Metastatic ovarian or colonic cancer: a clinical challenge.

Clinical problems arise when histology is unable to differentiate between an ovarian carcinoma infiltrating into the rectosigmoid region and a colonic cancer with ovarian metastases. To evaluate the discriminative value of immunohistochemistry we studied four groups: (A) ovarian carcinoma (n = 21), (B) ovarian carcinoma with sigmoid stenosis (n = 18), (C) colonic carcinoma (n = 20) and (D) a group in which the differential diagnosis was a problem (n = 19). Paraffin sections stained with a panel of monoclonal antibodies revealed specific patterns: in group A and B a negative Parlam-4 and positive OC-125; in group C the opposite; in group D the 'colonic' pattern in 15 cases, and the 'ovarian' pattern in only 2. The clinical diagnosis in group D during follow-up was ovarian carcinoma in 7, colonic carcinoma in 8, double tumour in 1 and still unknown in 3. This was based on high levels of serum tumour markers such as carcinoembryonic antigen (n = 5) and CA-125 (n = 4), laparotomy (n = 4), autopsy (n = 1), barium enema and/or endoscopy (n = 5). The response to chemotherapy in group D was extremely poor.