Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2013  |  Volume : 56  |  Issue : 4  |  Page : 396--398

Dumb-bell shaped poorly differentiated pelvic synovial sarcoma with molecular confirmation: A rare presentation of an uncommon disease entity


Roumina Hasan1, Sandeep Kumar2, Lakshmi Rao1,  
1 Department of Pathology, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
2 Department of Radiodiagnosis, Kasturba Medical College, Manipal University, Manipal, Karnataka, India

Correspondence Address:
Roumina Hasan
Departments of Pathology, Kasturba Medical College, Manipal University, Manipal, Karnataka
India

Abstract

Pelvic localization of synovial sarcoma is a rare phenomenon and to the best of our knowledge its presentation as a large DQdumb-bellDQ-shaped abdomino-pelvic mass showing extension to the thigh has never been reported in the literature. We report a case of a young adult presenting with retention of urine and was found to have a large abdomino-pelvic mass causing bony destruction and compression of pelvic viscera. A biopsy revealed a cellular tumor composed of spindle to oval cells arranged in a hemangiopericytomatous pattern. Histopathology was suggestive of poorly differentiated synovial sarcoma. Immunohistochemistry (IHC) was positive for vimentin, CD 99, Bcl2, Mic2 and focally for EMA and negative for CD 34, CK, desmin, synaptophysin, and WT1. Due to equivocal IHC findings molecular analysis was done which confirmed the diagnosis as synovial sarcoma.



How to cite this article:
Hasan R, Kumar S, Rao L. Dumb-bell shaped poorly differentiated pelvic synovial sarcoma with molecular confirmation: A rare presentation of an uncommon disease entity.Indian J Pathol Microbiol 2013;56:396-398


How to cite this URL:
Hasan R, Kumar S, Rao L. Dumb-bell shaped poorly differentiated pelvic synovial sarcoma with molecular confirmation: A rare presentation of an uncommon disease entity. Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Nov 24 ];56:396-398
Available from: https://www.ijpmonline.org/text.asp?2013/56/4/396/125336


Full Text

 Introduction



Synovial sarcoma is an aggressive, clinicopathologically, and cytogenetically distinctive tumor, accounting for 2.5-10.5% of all primary soft-tissue malignancies worldwide. [1] World Health Organization defines synovial sarcoma as "a mesenchymal spindle cell tumor which displays variable epithelial differentiation, including glandular formation and has a specific chromosomal translocation t(X;18)". [2]

The majority of synovial sarcomas occur in the extremities (85%-95%), with the site of predilection being around the knee and ankle joints. [1] Intra-abdominal synovial sarcomas are rare occurrences, only 34 cases have been reported till date, of which only few have been documented in the pelvis. [3]

We report this hitherto unknown presentation of a poorly differentiated synovial sarcoma as "dumb-bell"-shaped abdomino-pelvic mass lesion causing destruction of pelvic bones and showing extension into the thigh, with the radiological and pathological challenges in diagnosing it and discuss the treatment strategy to be employed in such cases.

 Case Report



A 17-year-old male was admitted to our hospital complaining of abdominal distension and non-colicky pain radiating to right thigh since 2 months. He presented to the emergency room with acute retention of urine. His physical examination revealed a large globular abdomino-pelvic mass in continuity with an indurated fixed, non-tender mass in medial side of right upper thigh.

CT scan abdomen revealed a large, lobulated heterogenously enhancing abdomino-pelvic mass lesion showing clumps and specks of calcification, with focal areas of necrosis within, extending superiorly from the right hemipelvis along the space of retzius up to the level of umbilicus, destroying the right superior and inferior pubic rami, anterior acetabular margins, and extending along the femoral canal and obturator foramen into the antero- medial aspect of right upper thigh [Figure 1]. CT thorax was negative for metastasis. Radiological possibilities suggested were Ewings sarcoma, malignant fibrous histiocytoma, and malignant peripheral nerve sheath tumor.{Figure 1}

An ultrasound guided percutaneous needle biopsy showed a cellular tumor composed of spindle to oval cells arranged in hemangiopericytomatous pattern and haphazardly. Cells had moderate eosinophilic cytoplasm, round to oval hyperchromatic nuclei, finely stippled chromatin, inconspicuous nucleolus, mild pleomorphism, brisk mitoses, and congested capillaries. Histopathology was suggestive of poorly differentiated synovial sarcoma [Figure 2].{Figure 2} Immunohistochemistry (IHC) was positive for vimentin, CD 99, Bcl2, Mic2 and focally for EMA and negative for CD 34, CK, desmin, synaptophysin, and WT1 [Figure 3]. Due to equivocal IHC findings molecular analysis was done. The reverse transcriptase-polymerase chain reaction (RT-PCR) revealed t(X;18) with SSX-SYT fusion protein which is diagnostic for synovial sarcoma and was negative for t(EWS-WTI), thereby ruling out desmoplastic small round cell tumor (DSRCT). Thus, a final diagnosis of poorly differentiated synovial sarcoma of pelvis, stage III, clinical group III was made. The management plan was for cytoreduction with neoadjuvant chemotherapy followed by surgery. Follow-up CT scan, post chemotherapy, revealed interval decrease in size of the mass lesion. Subsequently, the patient underwent right internal hemi-pelvectomy and the large abdomino-pelvic mass lesion was excised [Figure 4]. The excisional biopsy revealed treatment-induced changes with viable tumor less than 5% with marked endothelial proliferation. The inguinal lymph nodes and tumors pseudocapsule were found to be free of malignancy.{Figure 3}{Figure 4}

The patient is free of local recurrence or metastasis 12 months post surgery, and recovering well.

 Discussion



Synovial sarcomas typically occur in adolescents and young adult in the age group of 15-40 years, with no definite sex or race predilection. [1] Patients with synovial sarcoma usually present with a palpable soft-tissue mass or swelling. Pain is a consistent feature, distinguishing it from other soft tissue sarcomas which are typically painless. Synovial sarcomas can masquerade as a benign disease process due to its initial slow growth, long duration of symptoms, and well-defined margins especially when small in size.

Recent cDNA microarray-based studies found that the gene expression profile of synovial sarcoma is closely related to neural crest-derived malignant peripheral nerve sheath tumor. [4] Only six cases have been cited in the literature regarding pelvic synovial sarcomas, of which only two had molecular confirmation [Table 1]. [3],[5],[6],[7] We report this rare case of synovial sarcoma being confirmed with molecular analysis of t(X;18) translocation and the only such case to present as a large "dumb-bell"-shaped abdomino-pelvic mass.{Table 1}

Classical radiological finding of synovial sarcoma is the presence of calcification as seen in our case with "triple sign", which represents admixed area of low (calcification or fibrotic collagenized regions), intermediate (solid cellular elements), and high (hemorrhage or necrosis) signal areas within the mass on magnetic resonance imaging. [8]

Based on the prominence of either epithelioid or spindled cell type synovial sarcomas are histologically divided into four types: classic biphasic, monophasic fibrous, monophasic epithelial, and poorly differentiated (round cell) type.

Immunohistochemically synovial sarcomas are nearly uniformly positive for cytokeratin, Bcl2, EMA, CD99, and vimentin and negative for CD34, desmin, smooth muscle actin, and vascular tumor markers. S-100 are also expressed in 30% of synovial sarcomas. Calponin is frequently expressed in synovial sarcoma and their expression may be useful in distinguishing poorly differentiated variants from other round cell tumors which are always negative for this antigen. [9]

The IHC profile of our present case was unique as it was positive for vimentin, CD 99, Bcl2, and focally for EMA, but in contrast to most synovial sarcomas, CK7 was negative. Ewings sarcomas are characteristically CD 99 positive and CK 7 negative, but the presence of short spindly cells effectively ruled out its possibility. DSRCT was ruled out as they are positive for desmin, keratin, and synaptophysin and usually negative for CD 99, actin, and myogenin. DSRCT was conclusively ruled out by molecular analysis for t(EWS-WTI), which turned out to be negative. CD 34 was also negative ruling out hemangio-pericytoma.

The SYT-SSX fusion type has an impact on clinical behavior of synovial sarcoma, the overall survival being significantly better among SYT-SSX2 cases. [1],[2],[4]

The recent encouraging data regarding improved survival benefits of adjuvant chemotherapy in synovial sarcoma makes it pertinent to recognize this rare entity early and entertain it as a differential in abdomino-pelvic masses especially in adolescents and young adults.

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