ID: 38: PRIMARY SQUAMOS CELL CARCINOMA OF THE RECTUM

IntroductionSquamous cell carcinoma (SCC) of the gastrointestinal (GI) tract is an uncommon occurrence, as it usually involves the esophagus or anal canal. Approximately 90% of cases of rectal malignancy are adenocarcinoma and other rectal cancers include lymphoma (1.3%), carcinoid (0.4%), and sarcoma (0.3%). We are presenting a rare and unique case of patient with SCC of the rectum presenting with lower abdominal pain and significant weight loss.CaseA 52 year old female was admitted with a two month history of diffuse lower abdominal pain and hematochezia. The pain was constant and pressure like. The patient was a nonsmoker and nondrinker. Review of systems was pertinent for an unintentional weight loss of 10lbs. Physical examination revealed diffuse lower abdominal tenderness and a firm, irregular anterior rectal mass. She had no lymphadenopathy and her skin exam was normal. Laboratory results a normocytic anemia with a hemoglobin of 8.8 g/dl and a CEA of 1.35 ng/ml. Abdominal CT scan revealed a 7 cm irregular rectal mass with extra luminal compression to the rectosigmoid area, (figure 1). The mass did not extend from uterus and confirmed with transvaginal ultrasound. Patient underwent a flex sigmoidoscopy which revealed a lesion 5 cm from anal verge extending distally. There is a semi-circumferential narrowing occupying 7% of lumen and a dense layer of mass tissue with superficial friability of mucosa. Biopsy was taken from the mass, histology shows invasive moderately differentiated squamous cell carcinoma (figure 1).DiscussionSCC of the rectum has a very similar presentation to colon adenocarcinoma. Diagnoses can be established by proctoscopy/colonoscopy and more specifically, a biopsy to get a definitive histological analysis. The latter is a used to differentiate from SCC of the anus, which presents similarly. Immunohistochemistry has proved useful in characterizing lesions, especially when using cytokeratin stains. Pathogenesis is unclear due to its rarity; however one of the proposed mechanisms suggests that inflammation or infection results in squamous metaplasia from which carcinoma develops. Thus there is an association with HPV and various squamous cancers. In conclusion, SCC of rectum is a distinct entity and it is important to shed some light on this rare condition because it has different epidemiology, etiology, pathogenies and requires a different treatment approach than other colorectal carcinomas. Surgery is the primary treatment which c