A 30-year-old man presented with colicky abdominal pain in the left hemiabdomen of 3-month progression along with the sensation of fullness. Physical examination revealed a hard, fixed 8 x 8cm palpable mass in that area. Laboratory test results were normal. A contrast-enhanced abdominal computed tomography scan corroborated the presence of a mass in the left hemiabdomen. The patient underwent surgery resulting in the histologic diagnosis of synovial sarcoma (fig. 1).

Figure 1.

Contrast-enhanced coronal computed tomography multiplanar reconstruction in the venous phase showing a mass with no calcification with heterogeneous enhancement in the left hemiabdomen adjacent to the jejunal segments (A). Notice the metastatic satellite lesions with similar characteristics (B and C).

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Synovial sarcoma is the fourth most common type of soft-tissue sarcoma. Eighty to 95% of the cases present in the limbs. Fewer than 100 cases report it at the intra-abdominal level.1 The histologic subtypes are: monophasic, biphasic, and poorly differentiated. They arise from transposition (X; 18) and have a high mortality rate due to local tumor extension. Histopathologic and immunohistochemical diagnosis is indispensible.2 In tomography, the most frequent aspect of synovial sarcoma is that of a heterogeneous soft tissue mass with attenuation similar to that of intravenous contrast-enhanced muscle.3 Less attenuated areas representing bleeding or necrosis are also frequent. Small lesions tend to be homogeneous and well-defined margins are found in 53% of cases.