Synovial sarcoma (SS) is a rare soft-tissue malignancy. Only about 15% of SS originates from the retroperitoneum. Retroperitoneal SS (RSS) is usually diagnosed incidentally due to the anatomy of the retroperitoneum. The most common complaints of patients are abdominal and low back pain. Other common symptoms of RSS are palpable abdominal mass, weight loss, and anemia. In this study, we will describe a 29-year-old white Asian man with a diagnosis of RSS after radical nephrectomy. He was admitted to the Urology Department of Shohada-e Tajrish hospital, Tehran, Iran in March 2019. The distinguishing feature of this case is the size of the mass, which has never been reported so much for Retroperitoneal synovial sarcoma. Radiologic imaging showed a huge Retroperitoneal mass originating from the kidney. Based on the pathologic features and immunohistochemistry (IHC) study, the diagnosis was consistent with synovial sarcoma. Accurate diagnosis of RSS is usually based on the pathological findings. Therefore, in case of doubt, a biopsy can be employed. Surgical resection of the tumor and lymph nodes dissection is the main and most important part of the treatment. Aggressive resection with free margin is recommended. The role of adjuvant and neoadjuvant chemotherapy in RSS is not certain to date, but it is recommended according to the patient’ s condition.

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.

Introduction: sarcomas of retroperitoneum contain heterogeneous groups of tumors with varying histology, probability of complete resection, and propensity to recur and difficulty in development of effective treatment and challenging. In this article we present a case of recurrent myxoid Retroperitoneal liposarcoma in a patient with personal and family history of different cancers.

Liposarcoma are one of the common soft tissue sarcomas of adulthood which are remarkable because of their frequently large size. We report a case with an extremely large well-differentiated Retroperitoneal liposarcoma that weighted 32 kilograms. The patient had relapse about one year later and two recurrent tumors were successfully excised.

A 45-year-old man was diagnosed with Retroperitoneal ganglioneuroma. The tumor was a large encapsulated mass of firm consistency with a homogeneous, solid, grayish white-cut surface, having a focally edematous appearance (Figures, Top).