Introduction/Background Sarcomas are uncommon arising from mesenchymal elements anywhere in the body. Synovial Sarcoma or Malignant Synovioma arises from different types of soft tissues such as muscles and ligaments. It is classified into biphasic, monophasic or poorly differentiated. Biphasic is composed of epithelial cells, spindle fibroblast-like cells and few epitheloid cells. Monophasic type exhibit abundant spindle cells, epitheloid cells though lacking in clearly defined epithelial component.

Methodology Case of a 19 years old, nulligravid with hypogastric pain and abdominal mass. CT scan revealed complex illdefined mass, moderate ascites and clots. She underwent cytoreductive surgery with findings of pelvic mass attached to the right adnexa and uterus. Histopathologic result revealed malignant spindle cell neoplasm and immunohistochemical studies showed positive CD 99, TLE 1, Bcl-2, S100 and Desmin. Intraoperatively it is classified as Stage 1A according to AJCC Staging System.

Results It is caused by unique chromosomal translocations of t(X;18) (p11.2;q11.2) found in more than 90% of cases. Immunohistochemistry has been proven to be pivotal in its diagnosis. Initial surgery is an important prognostic factor.

Conclusion Synovial sarcoma rare type of soft tissue neoplasm affecting adolescents and young adults. It originates from primitive or uncommitted mesenchymal cells that differentiate to resemble synovial cells. It is caused by unique chromosomal translocations of t(X;18) (p11.2;q11.2) found in more than 90% of cases resulting in formation two fusion genes: SYT-SSX1 or SYT-SSX2. Immunohistochemical studies positive for TLE1, CD99, Bcl-2, S-100 and Desmin. These results are consistent showing reactivity with epithelial membrane antigen, cytokeratin, E-cadherin, S-100 in combination with CD34 negativity are useful and sensitive markers. Initial surgery is an important prognostic factor, it has a 5-year survival rate of 76% after cytoreductive surgery. Adjuvant chemotherapy with ifosfamide with doxorubicin may be given but there are no specific guidelines because of its rarity.