Synovial sarcoma is a malignant mesenchymal neoplasm which com-monly arises in the extremities of adults, in close association with joint capsules. Only a few cases of synovial sarcoma occurring in the abdominal wall have been reported. We report an extremely rare case of monophasic synovial sarcoma of abdominal wall in a 58-year-old woman who had presented with painless left ante-rior abdominal wallmass. The patient underwent excisional surgery. Histological andimmunohistochemistry examinations revealed monophasic synovial sarcoma. Base onthe diagnosis, the patient received chemoradiation. Primary synovial sarcoma is rarelyfound in the anterior abdominal wall. But, it should be included in the differentialdiagnosis.

Background: To the best of our knowledge, we do not have enough data on the rate of Intra-abdominal sarcoma (IaS) and retroperitoneal sarcoma (RPS) in Iran compared to other countries. We aimed to report a 10-year survey on the incidence and demographic characteristics or potential risk factors of RPS and IaS in Iranian patients in a population-based study setting. Materials and Methods: This descriptive-analytic, cross-sectional study was performed during 2009-2014 to evaluate the incidence of sarcomas in Iranian patients in different provinces under the supervision of the Cancer Research Center of Shahid Beheshti University of Medical Sciences. 2142 patients were included in this study. Demographic data of the patients including age, sex, and year of diagnosis, as well as primary tumor location and recurrence tumor site, tumor morphology, and tumor grade after clinical and pathological examinations were collected. Six-digit codes for histological grading and differentiation were used to evaluate the tumor grade. Data were entered into SPSS software, version 22, and analyzed. Results: In this study, data of 2142 patients were included and evaluated. Of the patients with soft tissue sarcoma, 993 (46. 4%) were women and 1149 (53. 6%) were men. Among the patients, 109 (5. 1%) were children, 1450 (67. 7%) were adults, and 583 (27. 2%) were in the elderly age group. The peak frequency of soft tissue sarcoma was 237 (11. 1%) in the 50-54 year-old age group, with the highest rate in 40-69 year-olds and the lowest in the age range of 5 to 14 years. The morphology of soft sarcomas was evaluated, gastrointestinal stromal sarcoma (16. 9%, n = 362) being the most common, followed by sarcoma (9. 9%, n = 212), spindle cell sarcoma (9. 9%, n = 211), leiomyosarcoma (7. 7%, n = 166%) and liposarcoma not otherwise specified (6. 2%, n = 133) were the four most common types. The morphology of the tumors was also evaluated by age and sex, which was statistically significant. gastrointestinal stromal sarcoma has the highest sex-specific incidence in patients with sarcoma, in other words, during the six years of our study, the sex-specific incidence rate for gastrointestinal stromal sarcoma were 163. 14 cases per 1000 patients with sarcoma for women, and the sex-specific incidence was 174. 6 for men. In patients less than 15 years old, the desmoplastic small round cell tumor morphology had the highest specific incidence, which was 201. 83 per 1000 patients with soft tissue sarcoma in this age group. Conclusion: Our study data show that the four most common types of soft tissue sarcomas in our country are gastrointestinal stromal sarcoma, followed by sarcoma, spindle cell sarcoma, leiomyosarcoma, and liposarcoma NOS and The peak age range of this sarcomas was 50-54 years.