Background: Synovial sarcoma usually arises in the extremities and in close proximity to large joints. Reported examples arising in the anterior abdominal wall are rare. Because most accounts from this location consist of case reports, neither clinical nor prognostic features have been well delineated.
Methods: Twenty-seven synovial sarcomas of the abdominal wall (SSAW), retrieved from the Soft Tissue Registry of the Armed Forces Institute of Pathology, were reviewed and analyzed retrospectively. Immunohistochemical stains were performed in 18 cases.
Results: There were specimens from 12 male and 15 female patients, ranging in age from 8 to 58 years (median, 23 years). The tumors were classified as biphasic (14), predominantly monophasic fibrous (8), and poorly differentiated (5) types. The neoplasms occasionally were cystic and typically reacted, at least focally, with antibodies directed against keratin and/or epithelial membrane antigen. Eight tumors were smaller than 5 cm.; 17 tumors were 5 cm or larger in size. Dimensions were not recorded in two cases. Follow-up, ranging from 1 to 264 months, was obtained in 18 cases. Nine individuals were alive and well and eight were dead of disease at median follow-up intervals of 98 and 26 months, respectively. One patient was dead with disease, possibly secondary to chemotherapy-related causes. All nine patients who have died had clinical evidence of metastatic disease. Patients who presented with tumors 5 cm or larger had a less favorable outcome than whose with tumors smaller than 5 cm. (58% versus 40% mortality). A positive correlation was noted between increased mitotic activity and the mortality rate. Although patients with biphasic and predominantly monophasic fibrous tumors had a similar mortality rate (40% for both groups), patients with poorly differentiated synovial sarcoma fared worse (100% mortality). In general, poorly differentiated synovial sarcomas had a higher mitotic rate than either biphasic or monophasic fibrous examples. No appreciable difference in survival was evident based on the age at presentation (< 15 versus > or = 15 years of age).
Conclusions: The survival rate for patients with SSAW is similar to that reported for synovial sarcoma in general. A high mitotic rate and the poorly differentiated subtype of synovial sarcoma both were associated with a poor prognosis and, to some extent, appear interrelated. Less favorable behavior also was noted when the tumors were large (> or = 5 cm). Pluripotential or arthrogenous mesenchyme may be implicated in the pathogenesis of these tumors.