Histopathology 1992, 20. 5 3 1 - 5 3 4


Intra-abdominal desmoplastic small round-cell tumour N.Y.A.CHEUNG, U.S.KHO0 8.1 K.W.CHAN Department of Pathology, University of Hong Kong, Queen Mary Hospital, Hong Kong Date of submission 28 August 1991 Accepted for publication 6 December 1991

Keywords: small round-cell tumour, desmoplastic reaction

Introduction Small round-cell tumours are a group of neoplasms, characterized by high cellularity, small cell size and a

generally diffuse pattern of growth, often seen in a paediatric population’. These include lymphomas, small cell variants of carcinomas, melanomas, rhabdomyosarcomas, neuroblastomas, primitive neuroectodermal tumours2, skeletal and extraskeletal Ewing’s sarcoma and Askin’s tumourj. The latter three share the common 11:2 2 chromosome translocation. Recently, a distinctive type of small round-cell tumour has been described

Figure 1 . Cross-section of the abdominal tumour showing the homogeneous whitish appearance.

Address for correspondence: Dr N.Y.A.Cheung, Department of Pathology. University of Hong Kong. Queen Mary Hospital, Pokfulam Road, Hong Kong.


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Figure 2. Islands of tumour cells separated by desmoplastic stroma.

showing a predilection for adolescent males, a predominant or exclusive intra-abdominal location, with only inconstant and secondary organ involvement, a nesting pattern of growth, focal rhabdoid features, intense desmoplastic reaction, immunohistochemical reactivity for epithelial, neural and muscle markers, and highly aggressive clinical b e h a v i ~ u r ' , ~We . have diagnosed such a tumour in a young Hong Kong Chinese.

Case report A 37-year-old man presented with a 2-week history of an abdominal mass. His general condition was satisfactory on examination. CAT-scan revealed several large masses in the abdomen. Laparotomy was performed during which three large tumour masses were found in the mesentery involving the serosa of the small bowel. Smaller tumour nodules were also found in the liver and the porta hepatis lymph nodes. No other tumours could be found in the chest, nasopharynx and other extraabdominal sites.


The resected tumour nodules weighed about 2 kg. They had a whitish bosselated surface. Sections showed a homogeneous whitish tumour (Figure 1). Microscopically. the tumour consisted of sharply outlined clusters of tumour cells separated by a desmoplastic stroma infiltrating the serosal layer of the bowel (Figure 2 ) . The tumour islands varied from large, solid, round to elongated appearance to areas of thin trabeculae or tiny clusters scattered in the stroma. Central necrosis was present in the larger tumour clusters. There were areas suggesting peripheral palisading. The tumour cells were uniform with small to medium sized nuclei which were mainly oval with hyperchromatic nuclei and inconspicuous nucleoli. The cytoplasm was scanty and cell borders indistinct. There was no evidence of glandular or squamous differentiation and intercellular bridging could not be demonstrated. The stroma between the tumour islands was predominantly collagenous but areas with myxoid change and necrosis were present.

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Figure 3 . Electronmicrograph showing primitive and tight junctions on the turnour cells. x 20000.

On immunohistochemical study, the tumour showed reactivity for epithelial cytokeratin (CAM 5.2 and Mak6) and epithelial membrane aritigen, neuron-specific enolase, desmin and vimentin. Staining for S-100 protein. leucocyte common antigen, actin, neurofilaments and chromogranin was negative. The glycogen and mucin content were inconspicuous. Ultrastructural studies showed that the tumour cells had a primitive appearance consistent with poorly differentiated carcinoma (Figure 3 ) . The cell membrane was smooth with primitive, intermediate and tight junctions identified. Basal lamina or microvilli were not found. The nuclei were irregular and the scanty cytoplasm contained a scattering of mitochondria, granular endoplasmic reticulum, occasional glycogen granules and Golgi apparatus. Perinuclear intermediate filaments and dense core granules could not be found.

Discussion The ultimate diagnosis of small round-cell tumours depends on the analysis of clinical, topographic, morphological, ultrastructural and immunohistochemical features5.Gerald et a).’ have recently described the intraabdominal desmoplastic small round-cell tumour based on their study of 19 such cases. The predominantly intra-abdominal location and prominent desmoplastic stroma, together with the co-expression of epithelial, neural and muscle immunohistochemical markers, distinguish this tumour from the other small round-cell tumours. No cytogenetic data have yet been available on this newly characterized small round-cell tumour. Some authors consider tumours with the capacity for simultaneous multi-directional phenotypic expression as a primitive ‘blastomatous’ Whether this


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tumour should be considered as a variant of the primitive primary neuro-ectodermal tumour of soft tissues or bone2,or whether it is related to the malignant small-cell tumour of the thoracopulmonary region in childhood (Askin's t ~ m o u ris) uncertain. ~ Chromosomal analysis would certainly be valuable in detecting the presence or absence of the 11:2 2 chromosome translocation, a finding consistently present in primitive neuroectodermal tumours, Ewing's sarcoma and Askin's tumour. According to Gerald et d.',this tumour may previously have been labelled as a n atypical example of one of the accepted types of small round-cell tumours, or as malignant mesothelioma, carcinoma, carcinoid or germ cell tumours. The aggressive clinical behaviour of the reported cases of this tumour fits the history of the present case. The tumour was only noticed by the patient 2 weeks before laparotomy. Pathologists should be acquainted with this entity, which should be included in the differential diagnosis of intra-abdominal small round-cell tumour. The histogenesis and behaviour of this tumour requires further investigation. It is especially important that cytogenetic studies be carried out on future cases in order to clarify its relationship with Ewing's sarcoma and Askin's tumour.

Acknowledgements We thank Dr Lily Ma for advice on the electronmicrographs.

References 1 . Gerald WL. Miller HK. Battifora H. Miettinen M. Silva EG. Rosai 1. Intra-abdominal desmoplastic small round-cell tumour. Report of 19 cases of a distinctive type of high-grade polyphenotypic malignancy affecting young individuals. Am. 1. Surg. Pathol. 1991: 15; 499-5 13. 2. rurgens H. Bier V. Harms D et a!. Malignant peripheral neuroectodermal tumours. A retrospective analysis of 42 patients. Cancer 1988: 61; 349-357. 3 . Askin FB. Rosai J. Sibley RK, Dehner LP. McAlister WH. Malignant small cell tumour of the thoracopulmonary region in childhood. A distinctive clinicopathologic entity of uncertain histogenesis. Canrer 1979: 43; 2438-2451. 4. Gonzalez-Crussi F. Crawford SE. Sun C-CJ. Intra-abdominal desmoplastic small-cell tumours with divergent differentiation. Observations on three cases of childhood. A m . 1. Surg. Pathol. 1 990; 14; 633-642. 5. Miettinen M. Imrnunohistochemistry of soft-tissue tumours. Possibilities and limitations in surgical pathology. Pathol. Anntr. 1990: 2 5 ; 1-36. 6 . Swanson PE. Dehner LP. Wick MR. Polyphenotypic small cell tumours of childhood (Abstract). Lab. hvest. 1988: 58;9.

Intra-abdominal desmoplastic small round-cell tumour.

Histopathology 1992, 20. 5 3 1 - 5 3 4 BRIEF REPORT Intra-abdominal desmoplastic small round-cell tumour N.Y.A.CHEUNG, U.S.KHO0 8.1 K.W.CHAN Departm...
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