Colonic or coelomic?

Abstract

In June, 2007, a 47-year-old woman of Irish descent presented with rectal bleeding, decreased appetite, weight loss, and decreased calibre of her stool. Her family history was signifi cant for reported, but unconfi rmed, early-onset colon cancer in three male and female fi rst-degree and second-degree relatives. Colonoscopy in May, 2006, had shown no abnormalities. Current colonoscopy showed an area of fi rm bulging with oedematous mucosa in the upper rectum. Biopsy showed small fragments of poorly diff erentiated invasive adenocarcinoma (fi gure A). MRI showed a 5·7 cm mass in the posterior wall of the rectosigmoid (fi gure B), with perirectal fat infi ltration and involvement of lymph nodes. Narrowing of the rectosigmoid lumen was seen, but the tumour seemed to be growing by extension into the perirectal fat rather than into the intestinal lumen. Endoscopic ultrasonography confi rmed these fi ndings. The staging was T3/T4 N1 M0, and the patient received neoadjuvant chemoradiation treatment, before undergoing a low anterior resection and diverting ileostomy in February, 2008. A six-cycle regimen of FOLFOX adjuvant chemotherapy was initiated. The pathological diagnosis was a pleiomorphic poorly diff erentiated adenocarcinoma involving the rectosigmoid colon. However, there was no defi nite origin from the colonic mucosal surface and highly bizarre cells with atypical mitotic activity were present. The immunohistochemistry profi le was CK7+, CK20–, CA-125+, ER+, CEA–, CDX2–, WT-1+, which raised the possibility of a gynaecological cancer. The presentation, location, and pathological fi ndings all suggested the diagnosis of a primary serous carcinoma arising from the visceral coelomic peritoneum or, less likely, a metastatic serous ovarian carcinoma, rather than rectal cancer. The patient underwent a subtotal abdominal hysterectomy with bilateral salpingo-oophorectomy in September, 2008. The pathology report mentioned only a few microscopic foci of high-grade serous carcinoma on the left paratubal and superfi cial cortex of the left ovary. These fi ndings were consistent with the fi nal pathological diagnosis of primary peritoneal serous adenocarcinoma. Given this diagnosis, genetic testing was done, showing a deleterious BRCA1 mutation, c.427 G>T, resulting in E143X, previously reported in Ireland. Our patient received three cycles of carboplatin and paclitaxel starting in December, 2008, and was in complete remission in February, 2010. Primary peritoneal adenocarcinoma, like ovarian cancer, often presents with non-specifi c gastrointestinal symptoms. A high degree of suspicion is needed for prompt identifi cation of this entity. In our case, as previously reported, the patient presented with symptoms of rectal bleeding and altered bowel habit, which are both suggestive of colorectal cancer. Also, secondary involvement of the colon by peritoneal carcinoma can mimic the colonoscopic appearance of a primary colon carcinoma—even modern imaging modalities cannot always distinguish between these two entities. An initial small biopsy showing “poorly diff erentiated adenocarcinoma” can, in the clinical context, be easily overlooked and interpreted as a primary cancer of the rectum if no immunohistochemistry is done. Any doubt, or presence of atypical morphologic features, should prompt careful pathological review and immunohistochemical assess ment. Notably, primary peritoneal serous adeno carcinoma is histologically and immunohisto chemically indis tinguish able from primary ovarian serous adeno carcinoma, and primary ovarian cancer must be excluded to establish the diagnosis. About 20% of women diagnosed with ovarian carcinoma at age 40–50 years carry a BRCA germline mutation. Female BRCA mutation carriers are also at a high risk for primary peritoneal carcinoma. Unusual presentations can delay the prompt identifi cation and appropriate management of this cancer.