An unexpected case of primary peritoneal carcinoma

Primary peritoneal carcinoma (PPC) is a rare tumor that is histologically and immunohistochemically indistinguishable from epithelial ovarian carcinoma. The diagnosis is usually made after excluding gross ovarian involvement or the ovarian involvement is only confined to the surface. A 68-year-old lady presented with right iliac fossa pain and increasing CA125. The CT scan showed bilateral pelvic adnexal masses with peritoneal deposits within the right side of abdomen. She was initially diagnosed as carcinomatosis peritonei from the omental cake removed after exploratory surgery. She was managed as advanced ovarian tumor with peritoneal metastasis and was then administered six cycles of chemotherapy. Surgical intervention included debulking surgery consisting of total abdominal hysterectomy, bilateral salpingo-oophorectomy and omentectomy and also with right hemicolectomy. The histopathological findings were of primary peritoneal serous carcinoma with only minimal involvement of the serosal surface of the right ovarian capsule. No microscopic invasion into underlying ovarian cortex and stroma was observed. Multiple tumor deposits were also seen over the right paratubal and paraovarian tissue, both parametrium as well as serosal surface of the terminal ileum and periappendicular tissue. Immunohistochemically, the malignant cells were positive to CA125, focally positive to CK7 and negative to CD20 and Calretinin. PPC is one of important differential diagnosis which needs to be considered in cases of advanced ovarian tumor, although the former can only be ascertained after excluding the ovarian involvement microscopically.