A Challenging Case of Metastatic Intra-Abdominal Synovial Sarcoma with Unusual Immunophenotype and Its Differential Diagnosis

Yi-Che Changchien,Ferenc Salamon,Gergő Papp,Zoltán Sápi,Uhrin Katalin,László Fónyad,János Fillinger

doi:10.1155/2012/786083

Abstract

The primary and metastatic gastrointestinal synovial sarcoma is rare with a wide differential diagnosis. It usually expresses cytokeratins EMA, BCL2 with an occasional CD99, and S100 positivity but not desmin. We present a case of metastatic synovial sarcoma with unusual immunophenotype causing diagnostic challenges. The tumor cells showed focal cytokeratin, EMA, and, unexpectedly, desmin positivity. Additional intranuclear TLE-1 positivity and negativity for CD34 and DOG-1 were also identified. A diagnosis of monophasic synovial sarcoma was confirmed by using FISH break-apart probe. RT-PCR revealed the SYT-SSX1 fusion gene. Intra-abdominal synovial sarcoma, either primary or metastatic, with unusual desmin positivity raises the diagnostic challenge, since a wide range of differential diagnoses could show a similar immunophenotype (leiomyosarcoma, desmoid tumor, myofibroblastic tumor, and rarely GIST etc.). Typical morphology and focal cytokeratin/EMA positivity should alert to this tumor, and FISH and RT-PCR remain the gold standard for the confirmation.

Highlights

Synovial sarcomas are rare, unique spindle cell tumors probably of mesenchymal cell origin [1]
The differential diagnosis is wide since gastrointestinal stromal tumor (GIST), solitary fibrous tumor, myogenic, and neurogenic tumors could have similar, if not identical morphology
We present a case of metastatic synovial sarcoma from a 26-year-old Hungarian male with unusual immunophenotype showing desmin positivity, which raises diagnostic challenges

Summary

Introduction

Unique spindle cell tumors probably of mesenchymal cell origin [1]. They occur most commonly in the young patients, representing about 10% of all soft tissue sarcomas and about 15–20% of cases in adolescents and young adults [2]. The differential diagnosis is wide since gastrointestinal stromal tumor (GIST), solitary fibrous tumor, myogenic, and neurogenic tumors could have similar, if not identical morphology. It usually expresses cytokeratin, EMA, BCL2 with occasional CD99, and S100 positivity. We present a case of metastatic synovial sarcoma from a 26-year-old Hungarian male with unusual immunophenotype showing desmin positivity, which raises diagnostic challenges

Case Report

Findings

Discussion

Conclusion