A Case of Primary Intra-abdominal Synovial Sarcoma

Abstract

Synovial sarcomas are relatively common intermediate-to-high-grade malignant soft tissue tumors, often with an initial indolent course. And among the sarcomas primary intra-abdominal synovial sarcoma is a relatively rare entity that may present with an abdominal mass and diagnosis is usually confirmed by immunohistochemistry. The authors report a case of a 46-year-old man who presented with a large palpable abdominal mass. Contrast-enhanced computed tomography (CT) scan showed a large welldefined heterogeneous intra-abdominal mass filling the entire pelvis and extending upwards till the subhepatic region causing displacement of intra-abdominal organs. However, no other focal lesions were seen in the solid organs. The same findings were confirmed on surgery. Histopathology was suggestive of desmoid tumor/hemangiopericytoma. Immunohistochemistry showed positive markers corresponding to synovial sarcoma. The patient was advised to undergo chemotherapy which was refused and follow-up was lost. After 10 months, patient presented for follow-up CT, which showed marked increase in size of the lesion.

A 64-year-old woman with primary synovial sarcoma of the abdominal wall

“…The SS corresponds up to approximately 10% of the soft tissue sarcomas, predominantly affect synovial structures in the extremities (up to 88%) of young adults, and more rarely derive from a sarcomatoid differentiation of peritoneal mesothelial cells simulating synovial tissue [1,[3][4][5][6][7][8][9][10][11]. Based on the pathological and IHC features there are three types of SS: (i) monophasic, with exclusively of spindle-shaped cells; (ii) biphasic, with epithelial and spindle cells; and (iii) poorly differentiated, with rhabdoid pattern [1][2][3][4][5][6][7][8][9][10][11]. Molecular biology resources can reveal specific gene rearrangement consistent with translocation of chromosomes X and 18, resulting in three alternative fusion products of the SS18 gene (SYT) with the SSX1, SSX2 or SSX4 gene [1][2][3][4][5][6][7][8][9][10][11].…”

“…Based on the pathological and IHC features there are three types of SS: (i) monophasic, with exclusively of spindle-shaped cells; (ii) biphasic, with epithelial and spindle cells; and (iii) poorly differentiated, with rhabdoid pattern [1][2][3][4][5][6][7][8][9][10][11]. Molecular biology resources can reveal specific gene rearrangement consistent with translocation of chromosomes X and 18, resulting in three alternative fusion products of the SS18 gene (SYT) with the SSX1, SSX2 or SSX4 gene [1][2][3][4][5][6][7][8][9][10][11]. Primary intra-abdominal SS is a very uncommon condition, which constitutes a challenging diagnosis due to non-specific symptoms.…”

“…The differential diagnosis includes carcinosarcoma, chondrosarcoma, choriocarcinoma, desmoid tumor, endometriosis, deep-seated fibromatosis, fibrosarcoma, gastrointestinal stromal tumor (GIST), histiocytoma, leiomyosarcoma, mesothelioma, rhabdomyosarcoma, schwannoma, small round cell tumor, and the very rare solitary fibrous tumor (SFT) [1-3, 7, 9-12]. Immunohistochemistry can be confirmatory because peritoneal mesothelial cells show mesenchymal and epithelial features and express filaments typical of mesoderm (vimentin) and epithelium (CKs) [1][2][3][4][5][6][7][9][10][11]. The worst outcomes, including recurrences and metastases of intra-abdominal SS, are associated with a diameter over 5 cm, young age, high mitotic count, retroperitoneal and pelvic sites, and vascular or neural invasion [1][2][3][7][8][9].…”

“…Synovial sarcoma (SS) is an intermediate-to-high-grade malignant mesenchymal tumor more often affecting soft tissues in the extremities and related with synovial structures, joint capsules, bursae and tendon sheaths of children and adults often with a longstanding course. Infrequent sites are head and neck, abdominal wall, mediastinum, lung and pleura, prostate and kidney, skin, blood vessels, and nerves [1][2][3][4][5][6][7][8][9][10][11]. Primary intra-abdominal SS is very uncommon, causing non-specific symptoms or compression of adjacent structures [1][2][3][4][5][6][7][8][9][10][11].…”

“…Infrequent sites are head and neck, abdominal wall, mediastinum, lung and pleura, prostate and kidney, skin, blood vessels, and nerves [1][2][3][4][5][6][7][8][9][10][11]. Primary intra-abdominal SS is very uncommon, causing non-specific symptoms or compression of adjacent structures [1][2][3][4][5][6][7][8][9][10][11]. Worthy of note is that the case reports of SS having origin from peritoneal structures are even rarer [2, 4-6, 10, 11].…”