2659 A Rare Occurrence: Anal Squamous Cell Carcinoma With Metastasis to Duodenum Causing Duodenal Stricture and Gastric Outlet Obstruction

Abstract

INTRODUCTION: Squamous cell carcinoma (SCC) of the anal canal is a rare entity encompassing only 2–4 percent of all colon, rectal, and anal cancers. SCC of the anal canal tends to be loco-regional and in the event of rare metastasis, most common sites of secondary seedlings are liver and lung. To our knowledge, metastatic spread from primary anal SCC to small bowel has been reported only once before. We report a rare case of SCC of anal canal with duodenal metastases in a 49-year-old female. CASE DESCRIPTION/METHODS: A 49-years-old female with 8-month history of anal SCC Stage IIIA, status post chemo-radiation therapy and loop ileostomy creation, was seen for complaints of vague abdominal pain, nausea, vomiting, and anorexia. Physical examination was significant for mild periumbilical tenderness. Computed tomography (CT) of the abdomen and pelvis with contrast revealed distended stomach with food contents and distended proximal duodenum. Esophagogastroduodenoscopy (EGD) showed moderate gastritis with duodenal edema resulting in narrowing of the second portion of the duodenum. An upper gastrointestinal series revealed distended stomach with air-fluid level and marked narrowing at the junction of the distal descending and transverse duodenum with "U-shaped" appearance and normal appearing jejunum. Colonoscopy via the stoma revealed normal colon proximal to diverting colostomy, normal terminal ileum, narrowed and scarred rectal vault. Biopsy from the duodenal stricture revealed duodenal mucosa with scattered malignant cells and malignant cell clusters within lymphatic spaces. Immunohistological staining demonstrated malignant cells positive for CK7, p16, p63 and negative for CK20, CDX2, GATA-3, CA19.9, TTF-1, Napsin A and PAX-8 favoring a metastatic anal SCC. DISCUSSION: Primary rectal squamous cell carcinomas (SCC) are very rare tumors. Additionally, either primary or metastatic SCC of the gastrointestinal tract is extremely rare with very few cases reported in the literature. In our case, the patient with established 8-month history of anal SCC stage IIIA, status post chemotherapy, radiation, and status post loop ileostomy creation presented with a rare duodenal metastasis, which has only been reported once before. The possibility of primary SCC of the small bowel was excluded with duodenal stricture biopsy showing scattered malignant cells and malignant cell clusters within lymphatic spaces and positive immunohistological staining favoring a metastatic lesion.