CLINICAL
AND
LABORATORY OBSERVATIONS
Malignant Peritoneal Mesothelioma in an Adolescent Male With BAP1 Deletion Steve Taylor, PA,* David Carpentieri, MD,* James Williams, MD,w Juan Acosta, MD,z and Richard Southard, MDy
Summary: Diffuse malignant peritoneal mesotheliomas in children are uncommon, aggressive tumors with a grave prognosis. We herein report the clinical, radiologic, and pathologic findings of a 16-year-old male. The adolescent presented with a history of abdominal pain, nausea and daily, nonbilious, nonbloody emesis for 3 weeks. Radiographic imaging suggested small bowel obstruction. The diagnostic work-up and differential diagnoses are discussed. Histologically, the tumor was composed of epithelioid cells with a papillary and glandular architectural pattern. A few glands appeared to produce mucinous material. Histochemistry revealed PAS diastase resistant mucin, an inconspicuous finding in diffuse malignant peritoneal mesothelioma. An extensive immunohistochemistry panel (calretinin, WT-1, D2-40, CK 7, CAM 5.2, CK 5/6, CEA, B72.3, CK 20, CD10, CD30, CD15, CD117, PLAP, S100, TFE3, and EMA) confirmed the diagnosis. Of special interest, BAP1 staining was cytoplasmic and consistent with 3p deletion detected by conventional cytogenetics. The ultrastructural analysis demonstrated long microvilli, desmosomes, and intercellular junctions which further supported the diagnosis. Key Words: malignant peritoneal mesothelioma, cytogenetics, histology, histochemistry, ultrastructural analysis, immunohistochemistry, BAP1
(J Pediatr Hematol Oncol 2015;37:e323–e327)
D
iffuse malignant peritoneal mesotheliomas (DMPM) in children are clinically rare and aggressive tumors which usually harbor a grave prognosis.1 Mesotheliomas may originate from mesothelial cells lining the pleura, peritoneal cavities, pericardium, or tunica vaginalis.2 Recent estimates report a prevalence of 10:1, glycogen deposits, desmosomes, and tonofilaments. These ultrastructural features supported the diagnosis of DMPM, epithelial subtype (Fig. 4). Conventional cytogenetic analysis of the tumor sample revealed a hyperdiploid karyotype: 82-87 , XXY, Y; + 1, del(1)(q13q44) 2; + 3, del(3)(p11p26)2; 5, 5 del(5)(q22q35); 6, 6, del(9)(q11q34); 10, add(11)(q13); 19, 21, 22, 22; and + 2-10mar[cp3].
DISCUSSION DMPM in the pediatric population is extremely uncommon and a comprehensive combination of patient
history, physical examination, radiographic, and pathologic findings are required to reach an accurate diagnosis.8 Patients typically present with nonspecific complaints like abdominal pain and distention, nausea and vomiting, diarrhea, weight loss, and ascites.9,10 As in our patient, small bowel obstruction may be a late feature with progression of disease.3 Radiologic studies are integral to the diagnosis, staging, surgical, and therapeutic management of peritoneal mesothelioma.3 CT scanning is the best imaging modality for this entity.1,3,8 The CT findings may show peritoneal/ omental nodules, irregular thickened areas of the peritoneum with or without ascites,8,9 or sheet-like growths of tumor encasing abdominal viscera.9 The radiologic differential diagnosis would include any peritoneal tumors seen in children: desmoplastic small round blue cell tumor, metastases from an adenocarcinoma, peritoneal endometriosis, and pseudomyxoma peritonei.8 Absence of a primary site may help distinguish peritoneal mesothelioma
TABLE 1. Immunohistochemical Panel With Results
Stain—Clone Cytokeratin—AE1/AE3/PCK26 Cytokeratin 7—SP52 Calretinin—SP65 Podoplanin—D2-40 Cytokeratin—CAM 5.2 Cytokeratin 5/6—D5/16 B4 WT-1—6F-H2 INI-1—MRQ-27 Cytokeratin 20—SP33 Epithelial membrane antigen—E29 TFE-3—H-300 CD10—SP67 HMB45 Placental alkaline phosphatase—NB10 CD30—BerH2 CD117—YR145 S100—Polyclonal CD15—MMA B72.3 Carcinoembryonic antigen—II-7 Chromogranin—DAK-A3 BAP-1—C-4
Result
Distributor
Positive Positive Positive Positive Positive Positive Positive Positive Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative
Ventana, Tucson, AZ Ventana, Tucson, AZ Ventana, Tucson, AZ CellMarque, Rocklin, CA BD Biosciences, San Jose, CA Dako, Carpenteria, CA Dako, Carpenteria, CA CellMarque, Rocklin, CA Ventana, Tucson, AZ Ventana, Tucson, AZ Santa Cruz Biotech, Santa Cruz, CA Ventana, Tucson, AZ Santa Cruz Biotech, Santa Cruz, CA Ventana, Tucson, AZ Ventana, Tucson, AZ CellMarque, Rocklin, CA Ventana, Tucson, AZ Ventana, Tucson, AZ Covance/Signet, Dedham, MA Dako, Carpenteria, CA Dako, Carpenteria, CA Santa Cruz Biotech, Santa Cruz, CA
e324 | www.jpho-online.com Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
Pediatric Mesothelioma With BAP1 Deletion
FIGURE 3. A, Hematoxylin and eosin of tumor with glandular and papillary patterns (magnification: 20); (B) calretinin strong, diffuse cytoplasmic positivity (magnification: 40); (C) WT-1 (clone 6F-H2) strong nuclear positivity (magnification: 20); (D) D2-40 positive along luminal surface of tumor cells (magnification: 20).
from a gastrointestinal or gynecologic adenocarcinoma,1 whereas retroperitoneal nodal enlargement favors an adenocarcinoma.8 Magnetic resonance imaging may provide superior staging information over CT in regards to surgical management.3 Fluorodeoxyglucose positron emission tomography also provides essential information as it may show both metabolically active components within cystic lesions11 and potential tumor response to therapy12 as well as assist in preselection of nodes or viable tumor to biopsy. In the majority of these cases there is peritoneal/ pleural fluid which may be harvested via minimally invasive procedures and submitted for cytologic interpretation. However, false negatives may occur from inadequate sampling, lack of shedding of malignant cells, or atypical
FIGURE 4. Electron micrograph demonstrating the typical 1015:1 (length vs. diameter) distribution of long, sinuous microvilli on the surface of a tumor cell in diffuse malignant peritoneal mesotheliomas stained with uranyl acetate and lead citrate (magnification: 8000).
Copyright
r
patterns of exfoliation making the differentiation of reactive from neoplastic cells difficult.13 The classic cytologic findings of abundant morular clusters of atypical mesotheliallike cells strongly support the diagnosis of mesothelioma.13 Cytology can be definitive in roughly one third of these cases; therefore, tissue biopsy will be pursued to assist in the diagnosis in the majority of the cases.3 The highest diagnostic yields are retrieved with an open biopsy when compared with CT-guided biopsy (60% with single pass and 85% with multiple attempts).3 In this case, no abdominal fluid was detected for cytopathologic analysis. The typical gross appearance is that of multiple diffuse and sometimes confluent nodules studding the peritoneal surfaces with possible extension into abdominal viscera.9 The lesions are usually firm, but may incorporate spongy/ cystic areas and range in size from minute to several centimeters. There are 4 main types of DMPM: epithelial (75%) comprising a tubulopapillary and nonglandular pattern (solid—13%), sarcomatous (6%), biphasic (6%), and undifferentiated; the latter may be composed of desmoplastic, lymphohistiocytoid, small cell, or deciduoid patterns.1,2 Borderline tumors or those with low malignant potential have either the well-differentiated papillary or multicystic patterns and are rare.1 Microscopically, the epithelial variant shows sheets of epithelioid cells with welldeveloped tubulopapillary structures.9,14 The tumor cells are round to polygonal with pale, eosinophilic cytoplasm, which may be vacuolated.9 Nuclei are vesicular and contain single, prominent nucleoli.15 Variable numbers of psammoma bodies and mitotic figures may be present.9,15 A few epithelial DMPM (2-5%) have mucin production demonstrable by mucicarmine stain, alcian blue/colloidal iron, or PAS-D.2 The sarcomatoid variant may contain homologous or heterologous elements.2 The biphasic pattern includes, in addition to the epithelial cells, a spindle cell component with hyperchromatic nuclei and prominent nucleoli surrounded by a minimal amount of eosinophilic
2014 Wolters Kluwer Health, Inc. All rights reserved.
www.jpho-online.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
e325
Taylor et al
cytoplasm.14 Aside from routine hematoxylin and eosin stains, special stains play only a minor role in aiding to establish a diagnosis. Histochemical studies, such as mucicarmine, PAS with/without diastase, and alcian blue/colloidal iron with/without hyaluronidase treatments assist in efforts to differentiate mucin-producing adenocarcinomas from mesotheliomas; however, approximately 2% to 5% of epithelial mesotheliomas will show positivity following treatments with diastase and hyaluronidase.2 The mucin component of our tumor was PAS with/without diastase positive, making this a rare entity and to the best of our knowledge only the third reported case. The histopathologic differential diagnosis of these peritoneal tumors relies heavily on the available clinical history, imaging, and in some part the sex of the patient.14 The most common pitfall in accurately diagnosing this disease occurs when the pathologist fails to recognize the myriad histologic patterns of epithelial, sarcomatous, and biphasic mesotheliomas.2 Epithelial neoplasms, including mesothelial hyperplasia or reactive multipotential subserosal cell proliferations, have to be differentiated from adenocarcinomas.2,14 The desmoplastic variant of undifferentiated DMPM poses a diagnostic challenge as it closely resembles fibrosing pleuritis.2 In regards to female patients, other types of papillary tumors need to be considered such as papillary serous carcinomas or multicystic mesotheliomas.14 Histoarchitectural features helpful in distinguishing papillary serous carcinoma from mesothelioma include cellular papillae with slitlike spaces, psammoma bodies, nuclear atypia, and mitoses; whereas in equivocal cases, adjunct studies such as immunohistochemistry and electron microscopy should aid in an accurate diagnosis.14 In our case, the initial suspicion for Xp11.2 translocation renal carcinoma was not supported by the battery of immunohistochemical stains and the absence of renal lesions by CT examination. There are no consensusbased guidelines/panels for immunostains to differentiate mesothelioma from other neoplasms.2,4,16 However, the literature2,4,9,14,16 suggests a panel comprised of 4 antibodies (2 positive and 2 negative) be utilized to differentiate mesotheliomas from adenocarcinomas.2,17 Distinguishing reactive mesothelial cell hyperplasia from malignant mesothelioma (one of the pitfalls mentioned above) may be accomplished with the use of desmin. Reactive mesothelial cells will stain positive with desmin, whereas mesotheliomas generally fail to express this marker.4 Epithelial mesotheliomas are positive for broad-spectrum cytokeratin (CK), CK 5/6, CK 7, calretinin, WT-1, thrombomodulin, D2-40, epithelial membrane antigen, mesothelin, and N-cadherin.2 Conversely, this subtype typically fails to express immunoreactivity with Ber-EP4, MOC-31, B72.3, BG-8, CD15/Leu-M1, and CEA.15 Our case displayed results within expected parameters except for positive EMA staining. In sarcomatoid variants, the majority of cells express broad-spectrum cytokeratin and vimentin and about 30% to 40% are positive for a-actin.2 Ultrastructural analysis is also helpful to distinguish adenocarcinomas from mesotheliomas. In the epithelial variant, cells show long, sinuous microvilli (10-15:1) not covered by a glycocalyx (as they are in pulmonary lesions) and do not anchor into rootlets in the underlying tumor cells.2,18 This variant also produces hyaluronic acid, seen as electron-dense material surfacing the neoplastic microvilli.2 Added to this, some cases will show extracellular or intraluminal crystalloid structures unique for mucin as was the case with our tumor. These tumor cells may also show desmosomes, intermediate filaments, a basement
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
membrane, and glycogen.19 The biphasic or mixed types display similar epithelial components; however, the fibrosarcomatous cells show elongated nuclei and well-developed rough-surfaced endoplasmic reticulum.18 Both fluorescent in situ hybridization (FISH) and cytogenetic analysis may be valuable adjuncts to support the diagnosis. Approximately 60% to 80% of mesotheliomas express deletions of 1p, 3p, 6q, 9p, 22q, and trisomy 7 or some combination thereof.13,20 In a retrospective study, Factor et al13 demonstrated that 57% of their negative or equivocal cases by cytology were reinterpreted as positive with adjunct testing, either karyotype or FISH. Further, their analysis revealed an improvement in the diagnosis of mesothelioma from 31% by karyotype alone to 58% when combined with FISH.13 As expected, cytogenetic analysis of this patient’s tumor tissue demonstrated near tetraploidy (82 to 87 chromosomes) with structural abnormalities involving the 1q, 3p, 6, 9q, and 22 chromosomes. Etiologic agents implicated in the pathogenesis of mesotheliomas are many and asbestos fibers prevail as the most common cause.8 However, in children the association between this agent and DMPM has not been established. Other proposed pathogenetic mechanisms include prior exposure to Simian Virus 40 (SV40), irradiation, and maternal treatment with isoniazid9,20,21; however, the literature supporting these etiologies are limited to anecdotal reports.7,21 The only salient past medical history reported in our patient was a gastroschisis repair shortly after birth. After reviewing the literature, this has not been reported to be a predisposing factor for development of peritoneal mesothelioma. The absence of a definitive etiologic agent strongly suggests the existence of an underlying genetic predisposition.9 BAP1 (locus at 3p21.1) has been shown to be a tumor suppressor in the BRCA1 pathway and recent studies have demonstrated germline alterations in BAP1 may predispose to the BAP1 cancer syndrome encompassing mesotheliomas, uveal melanomas, cutaneous melanomas, melanocytic BAP1mutated atypical intradermal tumors (MBAITS), and other cancer types.22,23 Furthermore, Yoshikawa et al24 found that BAP1 gene inactivation is more frequent in patients with the epithelial subtype of DMPM when compared with other subtypes and may be a useful marker in reaching a diagnosis. The immunohistochemical staining of our patient’s tissue with BAP1 demonstrated the absence of nuclear expression with only weak/focal cytoplasmic staining. This finding correlated with the cytogenetic analysis of our patient’s tumor sample which revealed a deletion of chromosome 3p. In analyzing the patient’s peripheral blood, no BAP1 germline mutation was detected indicating a somatic aberration in the tumor cells. No ages were provided in the study by Testa et al22 and in the meta-analysis by Carbone et al23 the ages ranged from 26 to 64 years of age. To the best of our knowledge, this is the first reported case of a BAP1 deletion in a pediatric patient with DMPM. Because of the rarity of this lesion and its infrequent occurrence in the pediatric population, reports on the prognosis are limited and often times conflicting. Nonetheless, the vast majority of these patients have a short survival (< 1 y)14 with a few studies showing the median time to be between 8 and 14 months.5,8 In an additional study, the 5-year survival rate for peritoneal versus pleural/ pericardial mesothelioma was 6%:17% (males) and 4%:7% (females), respectively.25 A standard therapeutic regimen has not been established. In 1 trial, cytoreduction surgery coupled with hyperthermic intraperitoneal chemotherapy
e326 | www.jpho-online.com Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
raised the median survival to about 5 years.26 Furthermore, patients who underwent complete parietal peritonectomies had a higher 5-year survival rate at 64% versus selective resections at 40%.27 Chemotherapeutic agents have shown some efficacy, including cisplatin, gemcitabine, and pemetrexed or combinations thereof.9 Milano et al11 report a case of an 11-year-old female treated with pemetrexed. This patient was in partial remission with stable disease 5 years after initial therapy.11 Radiotherapy offers no effective reduction in tumor burden and its efficacy in palliation is modest at best.9 Our patient was treated with a combination of cisplatin and pemetrexed administered every 3 weeks for a total of 6 cycles. He tolerated the treatment well with little side effects; however, after completion of chemotherapy imaging revealed scattered thickened foci throughout the abdomen which appeared to be along peritoneal surfaces as well as thickening around loops of intestine. An exploratory laparotomy and small bowel segmental resection confirmed the presence of multiple intestinal plaques with no evidence of tumor. Our patient is currently free of disease 27 months status-post initial diagnosis. In conclusion, we present a rare case of DMPM, mucin-producing epithelial subtype, affecting a 16-year-old male. Interestingly, the patient’s tumor contained a 3p deletion involving the BAP1 gene which may be implicated in the pathophysiology of this tumor. Clinicians and pathologists should recognize the importance of screening for BAP1 germline mutations in efforts to identify at-risk patients and their family members to enhance earlier detection and treatment of the lesions associated with this gene. The extremely limited occurrence in the pediatric population and myriad histologic profiles of this lesion may impart diagnostic difficulty for the practicing pediatric pathologist. Use of ancillary tests described herein, when combined with thorough clinical and radiologic evaluations, allows the pathologist to unequivocally diagnose this entity. Finally, better treatment protocols are needed to improve the dismal survival of these patients. ACKNOWLEDGMENTS The authors thank Dr Gary Mierau (Children’s Hospital of Denver, CO) for providing technical assistance with ultrastructural images and Dr Joseph Testa (Fox Chase Cancer Center, Philadelphia, PA) for assistance in the BAP1 immunohistochemical staining and mutation analysis. REFERENCES 1. Deraco M, Bartlett D, Kusamura S, et al. Consensus statement on peritoneal mesothelioma. J Surg Oncol. 2008;98:268–272. 2. Hammar S. Macroscopic, histologic, histochemical, immunohistochemical, and ultrastructural features of mesothelioma. Ultrastruct Pathol. 2006;30:3–17. 3. Moore AJ, Parker RJ, Wiggins J. Malignant mesothelioma. Orphanet J Rare Dis. 2008;3:34. 4. Arora SK, Srinivasan R, Nijhawan R, et al. Malignant biphasic peritoneal mesothelioma in a child: fine-needle aspiration cytology, histopathology, and immunohistochemical features along with review of literature. Diagn Cyatopathol. 2012;40:1112–1115.
Copyright
r
Pediatric Mesothelioma With BAP1 Deletion
5. Brenner J, Sordillo PP, Magill GB. Malignant mesothelioma in children: report of seven cases and review of the literature. Med Pediatr Oncol. 1981;9:367–373. 6. Kelsey A. Mesothelioma of childhood. Pediatr Hematol Oncol. 1994;11:461–462. 7. Fraire AE, Cooper S, Greenberg SD, et al. Mesothelioma of childhood. Cancer. 1988;62:838–847. 8. Wiggins J. BTS statement on malignant mesothelioma in the UK, 2007. Thorax. 2007;62(suppl 2):ii1–ii19. 9. Andre N, Agaimy A. Paediatric peritoneal mesothelioma. In: Schneider DT, et al, ed. Rare Tumors in Children and Adolescents. New York, NY: Springer-Verlag; 2012:313–319. 10. Paterson A, Grundy R, de Goyet Jde V, et al. Congential malignant peritoneal mesothelioma. Pediatr Radiol. 2003;33: 73–74. 11. Milano E, Pourroy B, Rome A, et al. Efficacy of a combination of pemetrexed and multiple redo-surgery in an 11-year-old girl with a recurrent multifocal abdominal mesothelioma. Anticancer Drugs. 2006;17:1231–1234. 12. Zervos MD, Bizekis C, Pass HI. Malignant mesothelioma 2008. Curr Opin Pulm Med. 2008;14:303–309. 13. Factor RE, Dal Cin P, Fletcher JA, et al. Cytogenetics and fluorescence in situ hybridization as adjuncts to cytology in the diagnosis of malignant mesothelioma. Cancer Cytopathol. 2009;117:247–253. 14. Moran CA, Albores-Saavedra J, Suster S. Primary peritoneal mesotheliomas in children: a clinicopathological and immunohistochemical study of eight cases. Histopathology. 2008;52: 824–830. 15. Kim J-H, Kwon K-Y, Jeon Y-K, et al. Mucin-positive epithelial mesothelioma of the peritoneum: small bowel involvement. Pathol Int. 2011;61:756–761. 16. Marchevsky AM. Application of immunohistochemistry to the diagnosis of malignant mesothelioma. Arch Pathol Lab Med. 2008;132:397–401. 17. Ordonez NG. The immunohistochemical diagnosis of mesothelioma: a comparative study of epithelioid mesothelioma and lung adenocarcinoma. Am J Surg Pathol. 2003;27:1031–1051. 18. Suzuki Y, Churg J, Kannerstein M. Ultrastructure of human malignant mesothelioma. Am J Pathol. 1976;85:241–251. 19. Weiss SW, Goldblum JR. Enzinger and Weiss’s Soft Tissue Tumors. 4th ed.. Philadelphia: Mosby; 2001:1083. 20. Robbins SL, Kumar V, Abbas AK, et al. Robbins and Cotran Pathologic Basis of Disease. 8th ed.. Philadelphia: Suanders Elsevier; 2010:733. 21. Manfredi JJ, Dong J, Liu WJ, et al. Evidence against a role for SV40 in human mesothelioma. Cancer Res. 2005;65:2602–2609. 22. Testa JR, Cheung M, Pei J, et al. Germline BAP1 mutations predispose to malignant mesothelioma. Nat Genet. 2011;43: 1022–1026. 23. Carbone M, Ferris LK, Baumann F, et al. BAP1 cancer syndrome: malignant mesothelioma, uveal and cutaneous melanoma, and MBAITs. J Transl Med. 2012;10:179. 24. Yoshikawa Y, Sato A, Tsujimura T, et al. Frequent inactivation of the BAP1 gene in epitheliod-type malignant mesothelioma. Cancer Sci. 2012;103:868–874. 25. Siesling S, van der Zwan JM, Izarzugaza I, et al. Rare thoracic cancers, including peritoneum mesothelioma. Eur J Cancer. 2012;48:949–960. 26. Baratti D, Kusamura S, Deraco M. Diffuse malignant peritoneal mesothelioma: systematic review of clinical management and biological research. J Surg Oncol. 2011;103:822–831. 27. Baratti D, Kusamura S, Cabras AD, et al. Cytoreductive surgery with selective versus complete parietal peritonectomy followed by hyperthermic intraperitoneal chemotherapy in patients with diffuse malignant peritoneal mesothelioma: a controlled study. Ann Surg Oncol. 2012;19:1416–1424.
2014 Wolters Kluwer Health, Inc. All rights reserved.
www.jpho-online.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
e327
AND
LABORATORY OBSERVATIONS
Malignant Peritoneal Mesothelioma in an Adolescent Male With BAP1 Deletion Steve Taylor, PA,* David Carpentieri, MD,* James Williams, MD,w Juan Acosta, MD,z and Richard Southard, MDy
Summary: Diffuse malignant peritoneal mesotheliomas in children are uncommon, aggressive tumors with a grave prognosis. We herein report the clinical, radiologic, and pathologic findings of a 16-year-old male. The adolescent presented with a history of abdominal pain, nausea and daily, nonbilious, nonbloody emesis for 3 weeks. Radiographic imaging suggested small bowel obstruction. The diagnostic work-up and differential diagnoses are discussed. Histologically, the tumor was composed of epithelioid cells with a papillary and glandular architectural pattern. A few glands appeared to produce mucinous material. Histochemistry revealed PAS diastase resistant mucin, an inconspicuous finding in diffuse malignant peritoneal mesothelioma. An extensive immunohistochemistry panel (calretinin, WT-1, D2-40, CK 7, CAM 5.2, CK 5/6, CEA, B72.3, CK 20, CD10, CD30, CD15, CD117, PLAP, S100, TFE3, and EMA) confirmed the diagnosis. Of special interest, BAP1 staining was cytoplasmic and consistent with 3p deletion detected by conventional cytogenetics. The ultrastructural analysis demonstrated long microvilli, desmosomes, and intercellular junctions which further supported the diagnosis. Key Words: malignant peritoneal mesothelioma, cytogenetics, histology, histochemistry, ultrastructural analysis, immunohistochemistry, BAP1
(J Pediatr Hematol Oncol 2015;37:e323–e327)
D
iffuse malignant peritoneal mesotheliomas (DMPM) in children are clinically rare and aggressive tumors which usually harbor a grave prognosis.1 Mesotheliomas may originate from mesothelial cells lining the pleura, peritoneal cavities, pericardium, or tunica vaginalis.2 Recent estimates report a prevalence of 10:1, glycogen deposits, desmosomes, and tonofilaments. These ultrastructural features supported the diagnosis of DMPM, epithelial subtype (Fig. 4). Conventional cytogenetic analysis of the tumor sample revealed a hyperdiploid karyotype: 82-87 , XXY, Y; + 1, del(1)(q13q44) 2; + 3, del(3)(p11p26)2; 5, 5 del(5)(q22q35); 6, 6, del(9)(q11q34); 10, add(11)(q13); 19, 21, 22, 22; and + 2-10mar[cp3].
DISCUSSION DMPM in the pediatric population is extremely uncommon and a comprehensive combination of patient
history, physical examination, radiographic, and pathologic findings are required to reach an accurate diagnosis.8 Patients typically present with nonspecific complaints like abdominal pain and distention, nausea and vomiting, diarrhea, weight loss, and ascites.9,10 As in our patient, small bowel obstruction may be a late feature with progression of disease.3 Radiologic studies are integral to the diagnosis, staging, surgical, and therapeutic management of peritoneal mesothelioma.3 CT scanning is the best imaging modality for this entity.1,3,8 The CT findings may show peritoneal/ omental nodules, irregular thickened areas of the peritoneum with or without ascites,8,9 or sheet-like growths of tumor encasing abdominal viscera.9 The radiologic differential diagnosis would include any peritoneal tumors seen in children: desmoplastic small round blue cell tumor, metastases from an adenocarcinoma, peritoneal endometriosis, and pseudomyxoma peritonei.8 Absence of a primary site may help distinguish peritoneal mesothelioma
TABLE 1. Immunohistochemical Panel With Results
Stain—Clone Cytokeratin—AE1/AE3/PCK26 Cytokeratin 7—SP52 Calretinin—SP65 Podoplanin—D2-40 Cytokeratin—CAM 5.2 Cytokeratin 5/6—D5/16 B4 WT-1—6F-H2 INI-1—MRQ-27 Cytokeratin 20—SP33 Epithelial membrane antigen—E29 TFE-3—H-300 CD10—SP67 HMB45 Placental alkaline phosphatase—NB10 CD30—BerH2 CD117—YR145 S100—Polyclonal CD15—MMA B72.3 Carcinoembryonic antigen—II-7 Chromogranin—DAK-A3 BAP-1—C-4
Result
Distributor
Positive Positive Positive Positive Positive Positive Positive Positive Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative
Ventana, Tucson, AZ Ventana, Tucson, AZ Ventana, Tucson, AZ CellMarque, Rocklin, CA BD Biosciences, San Jose, CA Dako, Carpenteria, CA Dako, Carpenteria, CA CellMarque, Rocklin, CA Ventana, Tucson, AZ Ventana, Tucson, AZ Santa Cruz Biotech, Santa Cruz, CA Ventana, Tucson, AZ Santa Cruz Biotech, Santa Cruz, CA Ventana, Tucson, AZ Ventana, Tucson, AZ CellMarque, Rocklin, CA Ventana, Tucson, AZ Ventana, Tucson, AZ Covance/Signet, Dedham, MA Dako, Carpenteria, CA Dako, Carpenteria, CA Santa Cruz Biotech, Santa Cruz, CA
e324 | www.jpho-online.com Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
Pediatric Mesothelioma With BAP1 Deletion
FIGURE 3. A, Hematoxylin and eosin of tumor with glandular and papillary patterns (magnification: 20); (B) calretinin strong, diffuse cytoplasmic positivity (magnification: 40); (C) WT-1 (clone 6F-H2) strong nuclear positivity (magnification: 20); (D) D2-40 positive along luminal surface of tumor cells (magnification: 20).
from a gastrointestinal or gynecologic adenocarcinoma,1 whereas retroperitoneal nodal enlargement favors an adenocarcinoma.8 Magnetic resonance imaging may provide superior staging information over CT in regards to surgical management.3 Fluorodeoxyglucose positron emission tomography also provides essential information as it may show both metabolically active components within cystic lesions11 and potential tumor response to therapy12 as well as assist in preselection of nodes or viable tumor to biopsy. In the majority of these cases there is peritoneal/ pleural fluid which may be harvested via minimally invasive procedures and submitted for cytologic interpretation. However, false negatives may occur from inadequate sampling, lack of shedding of malignant cells, or atypical
FIGURE 4. Electron micrograph demonstrating the typical 1015:1 (length vs. diameter) distribution of long, sinuous microvilli on the surface of a tumor cell in diffuse malignant peritoneal mesotheliomas stained with uranyl acetate and lead citrate (magnification: 8000).
Copyright
r
patterns of exfoliation making the differentiation of reactive from neoplastic cells difficult.13 The classic cytologic findings of abundant morular clusters of atypical mesotheliallike cells strongly support the diagnosis of mesothelioma.13 Cytology can be definitive in roughly one third of these cases; therefore, tissue biopsy will be pursued to assist in the diagnosis in the majority of the cases.3 The highest diagnostic yields are retrieved with an open biopsy when compared with CT-guided biopsy (60% with single pass and 85% with multiple attempts).3 In this case, no abdominal fluid was detected for cytopathologic analysis. The typical gross appearance is that of multiple diffuse and sometimes confluent nodules studding the peritoneal surfaces with possible extension into abdominal viscera.9 The lesions are usually firm, but may incorporate spongy/ cystic areas and range in size from minute to several centimeters. There are 4 main types of DMPM: epithelial (75%) comprising a tubulopapillary and nonglandular pattern (solid—13%), sarcomatous (6%), biphasic (6%), and undifferentiated; the latter may be composed of desmoplastic, lymphohistiocytoid, small cell, or deciduoid patterns.1,2 Borderline tumors or those with low malignant potential have either the well-differentiated papillary or multicystic patterns and are rare.1 Microscopically, the epithelial variant shows sheets of epithelioid cells with welldeveloped tubulopapillary structures.9,14 The tumor cells are round to polygonal with pale, eosinophilic cytoplasm, which may be vacuolated.9 Nuclei are vesicular and contain single, prominent nucleoli.15 Variable numbers of psammoma bodies and mitotic figures may be present.9,15 A few epithelial DMPM (2-5%) have mucin production demonstrable by mucicarmine stain, alcian blue/colloidal iron, or PAS-D.2 The sarcomatoid variant may contain homologous or heterologous elements.2 The biphasic pattern includes, in addition to the epithelial cells, a spindle cell component with hyperchromatic nuclei and prominent nucleoli surrounded by a minimal amount of eosinophilic
2014 Wolters Kluwer Health, Inc. All rights reserved.
www.jpho-online.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
e325
Taylor et al
cytoplasm.14 Aside from routine hematoxylin and eosin stains, special stains play only a minor role in aiding to establish a diagnosis. Histochemical studies, such as mucicarmine, PAS with/without diastase, and alcian blue/colloidal iron with/without hyaluronidase treatments assist in efforts to differentiate mucin-producing adenocarcinomas from mesotheliomas; however, approximately 2% to 5% of epithelial mesotheliomas will show positivity following treatments with diastase and hyaluronidase.2 The mucin component of our tumor was PAS with/without diastase positive, making this a rare entity and to the best of our knowledge only the third reported case. The histopathologic differential diagnosis of these peritoneal tumors relies heavily on the available clinical history, imaging, and in some part the sex of the patient.14 The most common pitfall in accurately diagnosing this disease occurs when the pathologist fails to recognize the myriad histologic patterns of epithelial, sarcomatous, and biphasic mesotheliomas.2 Epithelial neoplasms, including mesothelial hyperplasia or reactive multipotential subserosal cell proliferations, have to be differentiated from adenocarcinomas.2,14 The desmoplastic variant of undifferentiated DMPM poses a diagnostic challenge as it closely resembles fibrosing pleuritis.2 In regards to female patients, other types of papillary tumors need to be considered such as papillary serous carcinomas or multicystic mesotheliomas.14 Histoarchitectural features helpful in distinguishing papillary serous carcinoma from mesothelioma include cellular papillae with slitlike spaces, psammoma bodies, nuclear atypia, and mitoses; whereas in equivocal cases, adjunct studies such as immunohistochemistry and electron microscopy should aid in an accurate diagnosis.14 In our case, the initial suspicion for Xp11.2 translocation renal carcinoma was not supported by the battery of immunohistochemical stains and the absence of renal lesions by CT examination. There are no consensusbased guidelines/panels for immunostains to differentiate mesothelioma from other neoplasms.2,4,16 However, the literature2,4,9,14,16 suggests a panel comprised of 4 antibodies (2 positive and 2 negative) be utilized to differentiate mesotheliomas from adenocarcinomas.2,17 Distinguishing reactive mesothelial cell hyperplasia from malignant mesothelioma (one of the pitfalls mentioned above) may be accomplished with the use of desmin. Reactive mesothelial cells will stain positive with desmin, whereas mesotheliomas generally fail to express this marker.4 Epithelial mesotheliomas are positive for broad-spectrum cytokeratin (CK), CK 5/6, CK 7, calretinin, WT-1, thrombomodulin, D2-40, epithelial membrane antigen, mesothelin, and N-cadherin.2 Conversely, this subtype typically fails to express immunoreactivity with Ber-EP4, MOC-31, B72.3, BG-8, CD15/Leu-M1, and CEA.15 Our case displayed results within expected parameters except for positive EMA staining. In sarcomatoid variants, the majority of cells express broad-spectrum cytokeratin and vimentin and about 30% to 40% are positive for a-actin.2 Ultrastructural analysis is also helpful to distinguish adenocarcinomas from mesotheliomas. In the epithelial variant, cells show long, sinuous microvilli (10-15:1) not covered by a glycocalyx (as they are in pulmonary lesions) and do not anchor into rootlets in the underlying tumor cells.2,18 This variant also produces hyaluronic acid, seen as electron-dense material surfacing the neoplastic microvilli.2 Added to this, some cases will show extracellular or intraluminal crystalloid structures unique for mucin as was the case with our tumor. These tumor cells may also show desmosomes, intermediate filaments, a basement
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
membrane, and glycogen.19 The biphasic or mixed types display similar epithelial components; however, the fibrosarcomatous cells show elongated nuclei and well-developed rough-surfaced endoplasmic reticulum.18 Both fluorescent in situ hybridization (FISH) and cytogenetic analysis may be valuable adjuncts to support the diagnosis. Approximately 60% to 80% of mesotheliomas express deletions of 1p, 3p, 6q, 9p, 22q, and trisomy 7 or some combination thereof.13,20 In a retrospective study, Factor et al13 demonstrated that 57% of their negative or equivocal cases by cytology were reinterpreted as positive with adjunct testing, either karyotype or FISH. Further, their analysis revealed an improvement in the diagnosis of mesothelioma from 31% by karyotype alone to 58% when combined with FISH.13 As expected, cytogenetic analysis of this patient’s tumor tissue demonstrated near tetraploidy (82 to 87 chromosomes) with structural abnormalities involving the 1q, 3p, 6, 9q, and 22 chromosomes. Etiologic agents implicated in the pathogenesis of mesotheliomas are many and asbestos fibers prevail as the most common cause.8 However, in children the association between this agent and DMPM has not been established. Other proposed pathogenetic mechanisms include prior exposure to Simian Virus 40 (SV40), irradiation, and maternal treatment with isoniazid9,20,21; however, the literature supporting these etiologies are limited to anecdotal reports.7,21 The only salient past medical history reported in our patient was a gastroschisis repair shortly after birth. After reviewing the literature, this has not been reported to be a predisposing factor for development of peritoneal mesothelioma. The absence of a definitive etiologic agent strongly suggests the existence of an underlying genetic predisposition.9 BAP1 (locus at 3p21.1) has been shown to be a tumor suppressor in the BRCA1 pathway and recent studies have demonstrated germline alterations in BAP1 may predispose to the BAP1 cancer syndrome encompassing mesotheliomas, uveal melanomas, cutaneous melanomas, melanocytic BAP1mutated atypical intradermal tumors (MBAITS), and other cancer types.22,23 Furthermore, Yoshikawa et al24 found that BAP1 gene inactivation is more frequent in patients with the epithelial subtype of DMPM when compared with other subtypes and may be a useful marker in reaching a diagnosis. The immunohistochemical staining of our patient’s tissue with BAP1 demonstrated the absence of nuclear expression with only weak/focal cytoplasmic staining. This finding correlated with the cytogenetic analysis of our patient’s tumor sample which revealed a deletion of chromosome 3p. In analyzing the patient’s peripheral blood, no BAP1 germline mutation was detected indicating a somatic aberration in the tumor cells. No ages were provided in the study by Testa et al22 and in the meta-analysis by Carbone et al23 the ages ranged from 26 to 64 years of age. To the best of our knowledge, this is the first reported case of a BAP1 deletion in a pediatric patient with DMPM. Because of the rarity of this lesion and its infrequent occurrence in the pediatric population, reports on the prognosis are limited and often times conflicting. Nonetheless, the vast majority of these patients have a short survival (< 1 y)14 with a few studies showing the median time to be between 8 and 14 months.5,8 In an additional study, the 5-year survival rate for peritoneal versus pleural/ pericardial mesothelioma was 6%:17% (males) and 4%:7% (females), respectively.25 A standard therapeutic regimen has not been established. In 1 trial, cytoreduction surgery coupled with hyperthermic intraperitoneal chemotherapy
e326 | www.jpho-online.com Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Hematol Oncol
Volume 37, Number 5, July 2015
raised the median survival to about 5 years.26 Furthermore, patients who underwent complete parietal peritonectomies had a higher 5-year survival rate at 64% versus selective resections at 40%.27 Chemotherapeutic agents have shown some efficacy, including cisplatin, gemcitabine, and pemetrexed or combinations thereof.9 Milano et al11 report a case of an 11-year-old female treated with pemetrexed. This patient was in partial remission with stable disease 5 years after initial therapy.11 Radiotherapy offers no effective reduction in tumor burden and its efficacy in palliation is modest at best.9 Our patient was treated with a combination of cisplatin and pemetrexed administered every 3 weeks for a total of 6 cycles. He tolerated the treatment well with little side effects; however, after completion of chemotherapy imaging revealed scattered thickened foci throughout the abdomen which appeared to be along peritoneal surfaces as well as thickening around loops of intestine. An exploratory laparotomy and small bowel segmental resection confirmed the presence of multiple intestinal plaques with no evidence of tumor. Our patient is currently free of disease 27 months status-post initial diagnosis. In conclusion, we present a rare case of DMPM, mucin-producing epithelial subtype, affecting a 16-year-old male. Interestingly, the patient’s tumor contained a 3p deletion involving the BAP1 gene which may be implicated in the pathophysiology of this tumor. Clinicians and pathologists should recognize the importance of screening for BAP1 germline mutations in efforts to identify at-risk patients and their family members to enhance earlier detection and treatment of the lesions associated with this gene. The extremely limited occurrence in the pediatric population and myriad histologic profiles of this lesion may impart diagnostic difficulty for the practicing pediatric pathologist. Use of ancillary tests described herein, when combined with thorough clinical and radiologic evaluations, allows the pathologist to unequivocally diagnose this entity. Finally, better treatment protocols are needed to improve the dismal survival of these patients. ACKNOWLEDGMENTS The authors thank Dr Gary Mierau (Children’s Hospital of Denver, CO) for providing technical assistance with ultrastructural images and Dr Joseph Testa (Fox Chase Cancer Center, Philadelphia, PA) for assistance in the BAP1 immunohistochemical staining and mutation analysis. REFERENCES 1. Deraco M, Bartlett D, Kusamura S, et al. Consensus statement on peritoneal mesothelioma. J Surg Oncol. 2008;98:268–272. 2. Hammar S. Macroscopic, histologic, histochemical, immunohistochemical, and ultrastructural features of mesothelioma. Ultrastruct Pathol. 2006;30:3–17. 3. Moore AJ, Parker RJ, Wiggins J. Malignant mesothelioma. Orphanet J Rare Dis. 2008;3:34. 4. Arora SK, Srinivasan R, Nijhawan R, et al. Malignant biphasic peritoneal mesothelioma in a child: fine-needle aspiration cytology, histopathology, and immunohistochemical features along with review of literature. Diagn Cyatopathol. 2012;40:1112–1115.
Copyright
r
Pediatric Mesothelioma With BAP1 Deletion
5. Brenner J, Sordillo PP, Magill GB. Malignant mesothelioma in children: report of seven cases and review of the literature. Med Pediatr Oncol. 1981;9:367–373. 6. Kelsey A. Mesothelioma of childhood. Pediatr Hematol Oncol. 1994;11:461–462. 7. Fraire AE, Cooper S, Greenberg SD, et al. Mesothelioma of childhood. Cancer. 1988;62:838–847. 8. Wiggins J. BTS statement on malignant mesothelioma in the UK, 2007. Thorax. 2007;62(suppl 2):ii1–ii19. 9. Andre N, Agaimy A. Paediatric peritoneal mesothelioma. In: Schneider DT, et al, ed. Rare Tumors in Children and Adolescents. New York, NY: Springer-Verlag; 2012:313–319. 10. Paterson A, Grundy R, de Goyet Jde V, et al. Congential malignant peritoneal mesothelioma. Pediatr Radiol. 2003;33: 73–74. 11. Milano E, Pourroy B, Rome A, et al. Efficacy of a combination of pemetrexed and multiple redo-surgery in an 11-year-old girl with a recurrent multifocal abdominal mesothelioma. Anticancer Drugs. 2006;17:1231–1234. 12. Zervos MD, Bizekis C, Pass HI. Malignant mesothelioma 2008. Curr Opin Pulm Med. 2008;14:303–309. 13. Factor RE, Dal Cin P, Fletcher JA, et al. Cytogenetics and fluorescence in situ hybridization as adjuncts to cytology in the diagnosis of malignant mesothelioma. Cancer Cytopathol. 2009;117:247–253. 14. Moran CA, Albores-Saavedra J, Suster S. Primary peritoneal mesotheliomas in children: a clinicopathological and immunohistochemical study of eight cases. Histopathology. 2008;52: 824–830. 15. Kim J-H, Kwon K-Y, Jeon Y-K, et al. Mucin-positive epithelial mesothelioma of the peritoneum: small bowel involvement. Pathol Int. 2011;61:756–761. 16. Marchevsky AM. Application of immunohistochemistry to the diagnosis of malignant mesothelioma. Arch Pathol Lab Med. 2008;132:397–401. 17. Ordonez NG. The immunohistochemical diagnosis of mesothelioma: a comparative study of epithelioid mesothelioma and lung adenocarcinoma. Am J Surg Pathol. 2003;27:1031–1051. 18. Suzuki Y, Churg J, Kannerstein M. Ultrastructure of human malignant mesothelioma. Am J Pathol. 1976;85:241–251. 19. Weiss SW, Goldblum JR. Enzinger and Weiss’s Soft Tissue Tumors. 4th ed.. Philadelphia: Mosby; 2001:1083. 20. Robbins SL, Kumar V, Abbas AK, et al. Robbins and Cotran Pathologic Basis of Disease. 8th ed.. Philadelphia: Suanders Elsevier; 2010:733. 21. Manfredi JJ, Dong J, Liu WJ, et al. Evidence against a role for SV40 in human mesothelioma. Cancer Res. 2005;65:2602–2609. 22. Testa JR, Cheung M, Pei J, et al. Germline BAP1 mutations predispose to malignant mesothelioma. Nat Genet. 2011;43: 1022–1026. 23. Carbone M, Ferris LK, Baumann F, et al. BAP1 cancer syndrome: malignant mesothelioma, uveal and cutaneous melanoma, and MBAITs. J Transl Med. 2012;10:179. 24. Yoshikawa Y, Sato A, Tsujimura T, et al. Frequent inactivation of the BAP1 gene in epitheliod-type malignant mesothelioma. Cancer Sci. 2012;103:868–874. 25. Siesling S, van der Zwan JM, Izarzugaza I, et al. Rare thoracic cancers, including peritoneum mesothelioma. Eur J Cancer. 2012;48:949–960. 26. Baratti D, Kusamura S, Deraco M. Diffuse malignant peritoneal mesothelioma: systematic review of clinical management and biological research. J Surg Oncol. 2011;103:822–831. 27. Baratti D, Kusamura S, Cabras AD, et al. Cytoreductive surgery with selective versus complete parietal peritonectomy followed by hyperthermic intraperitoneal chemotherapy in patients with diffuse malignant peritoneal mesothelioma: a controlled study. Ann Surg Oncol. 2012;19:1416–1424.
2014 Wolters Kluwer Health, Inc. All rights reserved.
www.jpho-online.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
e327
