S3607 A Rare Case of Rectal Squamous Cell Carcinoma Metastatic to the Bile Duct

Introduction: Squamous cell carcinoma (SCC) of the gastrointestinal tract (GI) tract is rare outside of the esophagus and anus. SCC of the biliary tree is exceedingly uncommon and accounts for ∼2% of biliary tree malignancies, while rectal SCC comprises <1% of rectal cancers. To our knowledge, metastatic rectal SCC involving the bile ducts has not been previously reported. We present a unique case of a patient with a recto-vaginal fistula and jaundice who was found to have biopsy-proven SCC in the rectum and bile duct. Case Description/Methods: A 47-year-old woman with a past medical history of polysubstance abuse and untreated genital human papillomavirus (HPV) infection who was admitted to the hospital due to painless jaundice and passage of stool from the vagina for about 3 months prior to admission. Computed topography of the abdomen and pelvis showed evidence of a recto-vaginal fistula and diffuse dilation of proximal common bile duct (CBD) and intra-hepatic ducts. Endoscopic ultrasound showed a dilated CBD without a discrete mass. Endoscopic retrograde cholangiopancreatography (ERCP) revealed a CBD stricture; brushings and biopsies were obtained; the stricture was dilated, and a stent was placed. Flexible sigmoidoscopy revealed a circumferential fungating rectal mass; biopsies were obtained. Histopathology from both sites demonstrated SCC arising in a background of high-grade squamous intraepithelial lesions. Gynecologic oncology was consulted, and a diagnosis of metastatic rectal squamous cell carcinoma to the bile duct was favored, given a normal cervical examination aside from the presence of the recto-vaginal fistula. Plans were made to initiate chemotherapy ± immunotherapy after a multidisciplinary discussion. Discussion: This case highlights a rare presentation of SCC involving both the biliary system and rectum, an association not previously described in the literature. Given the absence of standardized treatment protocols for metastatic rectal SCC and the poor reported prognosis (∼8% survival), a multidisciplinary approach to care is recommended to guide management and improve outcomes.