SRU TOSHIBA RESIDENT TEACHING CASE
Sclerosing Angiomatoid Nodular Transformation of the Spleen Megan Lee, MD,* Melanie Caserta, MD,Þ and Hisham Tchelepi, MDþ CLINICAL HISTORY A 38-year-old female patient without significant past medical history initially presented with upper abdominal discomfort associated with nausea. Laboratory values were unremarkable, including amylase, lipase, and liver function tests. Hematologic laboratory values were as follows: hemoglobin level, 13.5 g/dL; white blood cell count, 12,900; and platelet count, 224,000. The patient was initially evaluated with an abdominal ultrasound, which demonstrated a 5.2-cm hypoechoic hypervascular mass within the spleen. A multiphasic contrastenhanced computed tomography (CT) of the abdomen was then performed for further evaluation. Computed tomography imaging demonstrated a hypervascular mass measuring 5.1 4.7 cm in the spleen with well-defined margins. The lesion was hypodense compared with the surrounding splenic tissue on noncontrast images. Avid peripheral contrast enhancement was seen during the early arterial phase of imaging, with a central area of hypoenhancement. On delayed imaging, the central areas of the lesion began to demonstrate contrast enhancement, with the entire lesion beginning to more closely approximate the contrast enhancement pattern of the surrounding splenic parenchyma. On imaging, this lesion within the spleen was favored to represent a hamartoma, with additional differential diagnostic considerations including hemangioma and angiosarcoma favored to be less likely. Given the concern for a possible malignancy, the patient was treated with splenectomy. Gross pathologic analysis of the splenic mass revealed ‘‘multiple tan well-defined nodulesI ranging from 0.8 cm up to 1.2 cm.’’
of benign massYforming lesions in the spleen with characteristic morphologic features and immunophenotypes. Sclerosing angiomatoid nodular transformation most commonly affects middleaged adults, with a slight female predominance. Most of these lesions are discovered incidentally in asymptomatic patients. Symptomatic patients most commonly present with abdominal pain, splenomegaly, or a palpable left upper quadrant mass.2 Sclerosing angiomatoid nodular transformation arises from the red pulp of the spleen and is ‘‘characterized by a single large mass composed of numerous variably sized vascular (angiomatoid) nodules separated by fibrous stroma.’’3 Several benign and malignant lesions are within the differential diagnosis of SANT radiographically. Benign vascular lesions such as littoral cell angiomas, hemangiomas, and hamartomas may have similar imaging characteristics. Additional differential diagnostic considerations should include hemangioendotheliomas, inflammatory myofibroblastic tumor, angiosarcoma, and metastases with associated reactive nodular transformation.3 Histologically, SANT lesions are composed of nodules each containing 3 distinct types of blood vessels as follows: splenic cord-type capillaries, sinusoidtype spaces, and small veins,4 separated by a central fibrous stroma. In comparison, littoral cell angiomas, hemangiomas, and hamartomas are characterized by aggregates of cells corresponding to a single type of blood vessel. Although there are only a small number of cases of SANT in the literature with reported radiologic findings, there
DIAGNOSIS The pathologic diagnosis was sclerosing angiomatoid nodular transformation (SANT) of the spleen.
DISCUSSION Sclerosing angiomatoid nodular transformation is a rare benign proliferative vascular lesion affecting the spleen. Sclerosing angiomatoid nodular transformation is a descriptive term first proposed by Martel et al1 in 2004 in a report of 25 cases
*Department of Radiology, Wake Forest School of Medicine; †Department of Radiology, Wake Forest Baptist Medical Center, Winston-Salem, NC; and ‡Department of Radiology, Keck School of Medicine-University of Southern California, Los Angeles, CA. The authors declare no conflict of interest. Reprints: Megan Lee, MD, Department of Radiology, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157 (e-mail: [email protected]). Copyright * 2014 by Lippincott Williams & Wilkins
Ultrasound Quarterly
& Volume 30, Number 3, September 2014
FIGURE 1. Transabdominal transverse gray scale ultrasonography image of the spleen demonstrating a large hypoechoic mass within the spleen with relatively well-defined margins. www.ultrasound-quarterly.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
241
Ultrasound Quarterly
Lee et al
& Volume 30, Number 3, September 2014
FIGURE 2. Color Doppler (A) and power Doppler (B) ultrasonography images of the spleen demonstrating a hypervascular mass with significantly increased peripheral vascularity and a spoke-wheel pattern of blood flow in the center of the lesion.
seem to be some common imaging features of SANT. On ultrasound, the echogenicity of SANT is variable, although lesions are more frequently hypoechoic with respect to the normal surrounding splenic parenchyma (Fig. 1). On color Doppler imaging, SANT lesions are hypervascular, demonstrating arterial flow signals with low resistive indices5 (Fig. 2). In comparison, splenic hemangiomas and hamartomas tend to be hyperechoic relative to the surrounding splenic parenchyma. Littoral cell angiomas can be isoechoic, hypoechoic, or hyperechoic, but tend to be multiple in number unlike SANT, which typically presents as a single splenic lesion. Unfortunately, hemangioendothelioma and angiosarcoma are typically hypoechoic and hypervascular by sonography, making differentiation between benign lesions such as SANT and malignant lesions difficult.6 Several case reports in the literature have examined the possible utility of contrast-enhanced ultrasonography (CEUS) in the examination of SANT. Contrast-enhanced ultrasonography provides real-time evaluation of the enhancement pattern, vessel structure, and morphology within the lesion, which may be of utility in differentiating SANT lesions from other hypervascular splenic lesions, although further research into this topic is
FIGURE 3. Noncontrast CT of the abdomen demonstrating a hypoattenuating mass within the spleen.
242
www.ultrasound-quarterly.com
needed.5,7 Gutzeit et al7 described the enhancement pattern of SANT on CEUS as follows: arterial vessels in a ‘‘spoke wheel’’ visualized in the early arterial phase followed by progressive centripetal enhancement of the mass from the periphery toward the center. Contrast was nearly evenly distributed throughout the lesion by the portal venous phase (45Y60 seconds). On CT, SANT lesions are well-circumscribed masses that are slightly hypodense to the surrounding splenic parenchyma on noncontrast imaging (Fig. 3). The enhancement pattern observed on CT is consistent with the findings described on CEUS. Lesions demonstrate early peripheral enhancement, which extends centrally in a spoke-wheel pattern toward the center with progressive central enhancement on delayed imaging4 (Figs. 4, 5). The spoke-wheel pattern of enhancement corresponds to a ‘‘central stellate fibrous stoma with fibrous septa separating angiomatoid nodules.’’8 This pattern of contrast enhancement on CT is helpful in narrowing the differential diagnosis radiographically. Splenic hamartomas tend to be isoenhancing relative to the surrounding splenic tissue, whereas littoral cell angiomas tend to be multiple in number and remain hypoattenuating relative to the surrounding
FIGURE 4. Early arterial phase contrast-enhanced CT. Avid peripheral enhancement of the splenic mass with an area of central hypoenhancement. * 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Ultrasound Quarterly
& Volume 30, Number 3, September 2014
SANT of the Spleen
Sclerosing angiomatoid nodular transformation should be included in the differential diagnosis for any patient with a solid hypervascular splenic mass. Given the small number of cases of SANT reported in the literature, it remains to be seen whether or not prospective diagnosis of SANT based on radiologic findings alone will be possible. The imaging features of SANT remain nonspecific and, at this point, do not exclude malignant splenic lesions such as angiosarcoma and metastases. Although diagnosis can be obtained through percutaneous biopsy, the risks of hemorrhage and possible seeding of the biopsy tract in the case of malignancy are generally prohibitive, and most patients ultimately undergo splenectomy for definitive pathologic diagnosis.
REFERENCES FIGURE 5. Delayed phase contrast-enhanced CT. Equilibration of the enhancement throughout the splenic mass, which now enhances only slightly more avidly than the surrounding splenic tissue.
splenic parenchyma until delayed phase imaging where they become isointense to the spleen. Splenic hemangiomas are often mixed cystic and solid lesions, demonstrating avid enhancement of the solid areas with relative hypoenhancement of the cystic components.6 Hemangioendothelioma and angiosarcoma both classically demonstrate avid enhancement and may contain areas of necrosis; however, this appearance is difficult to differentiate from the avid peripheral enhancement and central hypoenhancement in SANT. Recent studies have begun to examine the behavior of SANT lesions on FDG-PET imaging. Several case reports in the literature have shown that the angiomatoid nodules in SANT demonstrate hypermetabolic activity on FDG-PET compared with background splenic activity.8,9 A central area of low FDG uptake is present, corresponding to the central area of hypoenhancement on CT. Sclerosing angiomatoid nodular transformation’s FDG avidity may relate to the abundance of inflammatory cells, including macrophages, myofibroblasts, lymphocytes, and plasma cells within the lesion, although more research is needed.8
* 2014 Lippincott Williams & Wilkins
1. Martel M, Cheuk W, Lombardi L, et al. Sclerosing angiomatoid nodular transformation (SANT): report of 25 cases of a distinctive benign splenic lesion. Am J Surg Pathol. 2004;28(10):1268Y1279. 2. Kornprat P, Beham-Schmid C, Parvizi M, et al. Incidental finding of sclerosing angiomatoid nodular transformation of the spleen. Wien Klin Wochenschr. 2012;124(3Y4):100Y103. ¨ nder S, Kosemehmetoglu K, Himmetoglu C 3. O ¸ , et al. Sclerosing angiomatoid nodular transformation (SANT) of spleen: a case report describing cytology, histology, immunoprofile and differential diagnosis. Cytopathology. 2012;23(2):129Y132. 4. Raman SP, Singhi A, Horton KM, et al. Sclerosing angiomatoid nodular transformation of the spleen (SANT): multimodality imaging appearance of five cases with radiology-pathology correlation. Abdom Imaging. 2013;38(4):827Y834. 5. Cao JY, Zhang H, Wang WP. Ultrasonography of sclerosing angiomatoid nodular transformation in the spleen. World J Gastroenterol. 2010;16(29):3727Y3730. 6. Abbott RM, Levy AD, Aguilera NS, et al. From the archives of the AFIP: primary vascular neoplasms of the spleen: radiologic-pathologic correlation. Radiographics. 2004;24(4):1137Y1163. 7. Gutzeit A, Stuckmann G, Dommann-Scherrer C. Sclerosing angiomatoid nodular transformation (SANT) of the spleen: sonographic finding. J Clin Ultrasound. 2009;37(5):308Y311. 8. Thacker C, Korn R, Millstine J, et al. Sclerosing angiomatoid nodular transformation of the spleen: CT, MR, PET, and 99(m)Tc-sulfur colloid SPECT CT findings with gross and histopathological correlation. Abdom Imaging. 2010;35(6):683Y689. 9. Feng YM, Huang YC, Tu CW, et al. Distinctive PET/CT Features of Splenic SANT. Clin Nucl Med. 2013.
www.ultrasound-quarterly.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
243
Sclerosing Angiomatoid Nodular Transformation of the Spleen Megan Lee, MD,* Melanie Caserta, MD,Þ and Hisham Tchelepi, MDþ CLINICAL HISTORY A 38-year-old female patient without significant past medical history initially presented with upper abdominal discomfort associated with nausea. Laboratory values were unremarkable, including amylase, lipase, and liver function tests. Hematologic laboratory values were as follows: hemoglobin level, 13.5 g/dL; white blood cell count, 12,900; and platelet count, 224,000. The patient was initially evaluated with an abdominal ultrasound, which demonstrated a 5.2-cm hypoechoic hypervascular mass within the spleen. A multiphasic contrastenhanced computed tomography (CT) of the abdomen was then performed for further evaluation. Computed tomography imaging demonstrated a hypervascular mass measuring 5.1 4.7 cm in the spleen with well-defined margins. The lesion was hypodense compared with the surrounding splenic tissue on noncontrast images. Avid peripheral contrast enhancement was seen during the early arterial phase of imaging, with a central area of hypoenhancement. On delayed imaging, the central areas of the lesion began to demonstrate contrast enhancement, with the entire lesion beginning to more closely approximate the contrast enhancement pattern of the surrounding splenic parenchyma. On imaging, this lesion within the spleen was favored to represent a hamartoma, with additional differential diagnostic considerations including hemangioma and angiosarcoma favored to be less likely. Given the concern for a possible malignancy, the patient was treated with splenectomy. Gross pathologic analysis of the splenic mass revealed ‘‘multiple tan well-defined nodulesI ranging from 0.8 cm up to 1.2 cm.’’
of benign massYforming lesions in the spleen with characteristic morphologic features and immunophenotypes. Sclerosing angiomatoid nodular transformation most commonly affects middleaged adults, with a slight female predominance. Most of these lesions are discovered incidentally in asymptomatic patients. Symptomatic patients most commonly present with abdominal pain, splenomegaly, or a palpable left upper quadrant mass.2 Sclerosing angiomatoid nodular transformation arises from the red pulp of the spleen and is ‘‘characterized by a single large mass composed of numerous variably sized vascular (angiomatoid) nodules separated by fibrous stroma.’’3 Several benign and malignant lesions are within the differential diagnosis of SANT radiographically. Benign vascular lesions such as littoral cell angiomas, hemangiomas, and hamartomas may have similar imaging characteristics. Additional differential diagnostic considerations should include hemangioendotheliomas, inflammatory myofibroblastic tumor, angiosarcoma, and metastases with associated reactive nodular transformation.3 Histologically, SANT lesions are composed of nodules each containing 3 distinct types of blood vessels as follows: splenic cord-type capillaries, sinusoidtype spaces, and small veins,4 separated by a central fibrous stroma. In comparison, littoral cell angiomas, hemangiomas, and hamartomas are characterized by aggregates of cells corresponding to a single type of blood vessel. Although there are only a small number of cases of SANT in the literature with reported radiologic findings, there
DIAGNOSIS The pathologic diagnosis was sclerosing angiomatoid nodular transformation (SANT) of the spleen.
DISCUSSION Sclerosing angiomatoid nodular transformation is a rare benign proliferative vascular lesion affecting the spleen. Sclerosing angiomatoid nodular transformation is a descriptive term first proposed by Martel et al1 in 2004 in a report of 25 cases
*Department of Radiology, Wake Forest School of Medicine; †Department of Radiology, Wake Forest Baptist Medical Center, Winston-Salem, NC; and ‡Department of Radiology, Keck School of Medicine-University of Southern California, Los Angeles, CA. The authors declare no conflict of interest. Reprints: Megan Lee, MD, Department of Radiology, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157 (e-mail: [email protected]). Copyright * 2014 by Lippincott Williams & Wilkins
Ultrasound Quarterly
& Volume 30, Number 3, September 2014
FIGURE 1. Transabdominal transverse gray scale ultrasonography image of the spleen demonstrating a large hypoechoic mass within the spleen with relatively well-defined margins. www.ultrasound-quarterly.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
241
Ultrasound Quarterly
Lee et al
& Volume 30, Number 3, September 2014
FIGURE 2. Color Doppler (A) and power Doppler (B) ultrasonography images of the spleen demonstrating a hypervascular mass with significantly increased peripheral vascularity and a spoke-wheel pattern of blood flow in the center of the lesion.
seem to be some common imaging features of SANT. On ultrasound, the echogenicity of SANT is variable, although lesions are more frequently hypoechoic with respect to the normal surrounding splenic parenchyma (Fig. 1). On color Doppler imaging, SANT lesions are hypervascular, demonstrating arterial flow signals with low resistive indices5 (Fig. 2). In comparison, splenic hemangiomas and hamartomas tend to be hyperechoic relative to the surrounding splenic parenchyma. Littoral cell angiomas can be isoechoic, hypoechoic, or hyperechoic, but tend to be multiple in number unlike SANT, which typically presents as a single splenic lesion. Unfortunately, hemangioendothelioma and angiosarcoma are typically hypoechoic and hypervascular by sonography, making differentiation between benign lesions such as SANT and malignant lesions difficult.6 Several case reports in the literature have examined the possible utility of contrast-enhanced ultrasonography (CEUS) in the examination of SANT. Contrast-enhanced ultrasonography provides real-time evaluation of the enhancement pattern, vessel structure, and morphology within the lesion, which may be of utility in differentiating SANT lesions from other hypervascular splenic lesions, although further research into this topic is
FIGURE 3. Noncontrast CT of the abdomen demonstrating a hypoattenuating mass within the spleen.
242
www.ultrasound-quarterly.com
needed.5,7 Gutzeit et al7 described the enhancement pattern of SANT on CEUS as follows: arterial vessels in a ‘‘spoke wheel’’ visualized in the early arterial phase followed by progressive centripetal enhancement of the mass from the periphery toward the center. Contrast was nearly evenly distributed throughout the lesion by the portal venous phase (45Y60 seconds). On CT, SANT lesions are well-circumscribed masses that are slightly hypodense to the surrounding splenic parenchyma on noncontrast imaging (Fig. 3). The enhancement pattern observed on CT is consistent with the findings described on CEUS. Lesions demonstrate early peripheral enhancement, which extends centrally in a spoke-wheel pattern toward the center with progressive central enhancement on delayed imaging4 (Figs. 4, 5). The spoke-wheel pattern of enhancement corresponds to a ‘‘central stellate fibrous stoma with fibrous septa separating angiomatoid nodules.’’8 This pattern of contrast enhancement on CT is helpful in narrowing the differential diagnosis radiographically. Splenic hamartomas tend to be isoenhancing relative to the surrounding splenic tissue, whereas littoral cell angiomas tend to be multiple in number and remain hypoattenuating relative to the surrounding
FIGURE 4. Early arterial phase contrast-enhanced CT. Avid peripheral enhancement of the splenic mass with an area of central hypoenhancement. * 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Ultrasound Quarterly
& Volume 30, Number 3, September 2014
SANT of the Spleen
Sclerosing angiomatoid nodular transformation should be included in the differential diagnosis for any patient with a solid hypervascular splenic mass. Given the small number of cases of SANT reported in the literature, it remains to be seen whether or not prospective diagnosis of SANT based on radiologic findings alone will be possible. The imaging features of SANT remain nonspecific and, at this point, do not exclude malignant splenic lesions such as angiosarcoma and metastases. Although diagnosis can be obtained through percutaneous biopsy, the risks of hemorrhage and possible seeding of the biopsy tract in the case of malignancy are generally prohibitive, and most patients ultimately undergo splenectomy for definitive pathologic diagnosis.
REFERENCES FIGURE 5. Delayed phase contrast-enhanced CT. Equilibration of the enhancement throughout the splenic mass, which now enhances only slightly more avidly than the surrounding splenic tissue.
splenic parenchyma until delayed phase imaging where they become isointense to the spleen. Splenic hemangiomas are often mixed cystic and solid lesions, demonstrating avid enhancement of the solid areas with relative hypoenhancement of the cystic components.6 Hemangioendothelioma and angiosarcoma both classically demonstrate avid enhancement and may contain areas of necrosis; however, this appearance is difficult to differentiate from the avid peripheral enhancement and central hypoenhancement in SANT. Recent studies have begun to examine the behavior of SANT lesions on FDG-PET imaging. Several case reports in the literature have shown that the angiomatoid nodules in SANT demonstrate hypermetabolic activity on FDG-PET compared with background splenic activity.8,9 A central area of low FDG uptake is present, corresponding to the central area of hypoenhancement on CT. Sclerosing angiomatoid nodular transformation’s FDG avidity may relate to the abundance of inflammatory cells, including macrophages, myofibroblasts, lymphocytes, and plasma cells within the lesion, although more research is needed.8
* 2014 Lippincott Williams & Wilkins
1. Martel M, Cheuk W, Lombardi L, et al. Sclerosing angiomatoid nodular transformation (SANT): report of 25 cases of a distinctive benign splenic lesion. Am J Surg Pathol. 2004;28(10):1268Y1279. 2. Kornprat P, Beham-Schmid C, Parvizi M, et al. Incidental finding of sclerosing angiomatoid nodular transformation of the spleen. Wien Klin Wochenschr. 2012;124(3Y4):100Y103. ¨ nder S, Kosemehmetoglu K, Himmetoglu C 3. O ¸ , et al. Sclerosing angiomatoid nodular transformation (SANT) of spleen: a case report describing cytology, histology, immunoprofile and differential diagnosis. Cytopathology. 2012;23(2):129Y132. 4. Raman SP, Singhi A, Horton KM, et al. Sclerosing angiomatoid nodular transformation of the spleen (SANT): multimodality imaging appearance of five cases with radiology-pathology correlation. Abdom Imaging. 2013;38(4):827Y834. 5. Cao JY, Zhang H, Wang WP. Ultrasonography of sclerosing angiomatoid nodular transformation in the spleen. World J Gastroenterol. 2010;16(29):3727Y3730. 6. Abbott RM, Levy AD, Aguilera NS, et al. From the archives of the AFIP: primary vascular neoplasms of the spleen: radiologic-pathologic correlation. Radiographics. 2004;24(4):1137Y1163. 7. Gutzeit A, Stuckmann G, Dommann-Scherrer C. Sclerosing angiomatoid nodular transformation (SANT) of the spleen: sonographic finding. J Clin Ultrasound. 2009;37(5):308Y311. 8. Thacker C, Korn R, Millstine J, et al. Sclerosing angiomatoid nodular transformation of the spleen: CT, MR, PET, and 99(m)Tc-sulfur colloid SPECT CT findings with gross and histopathological correlation. Abdom Imaging. 2010;35(6):683Y689. 9. Feng YM, Huang YC, Tu CW, et al. Distinctive PET/CT Features of Splenic SANT. Clin Nucl Med. 2013.
www.ultrasound-quarterly.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
243
