Squamous Cell Carcinoma of the Anus: An Unlikely Suspect for a Pancreatic Mass

Abstract

Introduction While rare in the United States, the incidence of squamous cell carcinoma of the anus (SCCA) has been increasing over the last three decades as infection with human immunodeficiency virus and human papillomavirus become more prevalent. SCCA is often confined locally at diagnosis, but in unusual circumstances can present with seemingly unrelated signs and symptoms. Case Presentation An 80-year-old woman presented with one week of lethargy, anorexia, and acholic stools. Her medical history was significant for Stage IIIB SCCA diagnosed five years prior and treated with concurrent chemoradiation. She received appropriate follow up including surveillance colonoscopy three years after treatment. Initial exam was significant for scleral icterus with corroborating liver enzymes: alkaline phosphatase 1327 IU/L, total bilirubin 11.8 mg/dL, and direct bilirubin 9.5 mg/dL. Ultrasound was notable for extrahepatic biliary ductal dilation with enlargement of the pancreatic head. Computed tomography of the abdomen revealed an infiltrative mass centered at the dorsal pancreas encasing the superior mesenteric artery, celiac trunk, and distal common bile duct favored to be a locally advanced pancreatic ductal adenocarcinoma. Endoscopic ultrasound confirmed two hypoechoic masses surrounding the celiac artery and common bile duct; a biliary stent was placed with relief of symptoms and both masses sampled via fine needle aspiration. Pathology demonstrated a morphologic and phenotypic match between the current tumor and her prior SCCA (positive CK5/6, CK7, p63, p16 and negative CK20) indicating recurrence of SCCA with metastasis to the pancreas. Chemotherapy and immunotherapy directed against the programmed cell death (PD) receptor-1 were considered but ultimately not offered given her poor performance status and weakly positive staining for PD-ligand-1. She received palliative radiation and was discharged home with hospice services. Discussion Classically, SCCA is a local disease that rarely metastasizes, but on occasion can present distally in the lungs, liver, and regional lymph nodes. Distant spread to the pancreas is incredibly unique, and adds to the limited case reports of SCCA metastasizing to unusual locations including the vulva and biliary epithelium. For patients with a history of SCCA, any mass should raise suspicion for metastasis and confirmed with tissue diagnosis as novel treatment options may be offered in the current era of advancing immunotherapy.