A rare case of primary rectal squamous cell carcinoma diagnosed by endoscopic ultrasound.

Primary squamous cell carcinoma (SCC) of the rectum is a very rare entity making up to 0.1-0.25/1,000 cases of all colorectal cancers. Here, we present the case of an otherwise healthy 63-year-old female who presented with progressive pelvic discomfort, new onset constipation and a complex mass in presacral region on imaging which was proved to be poorly differentiated SCC of the rectum. The correct diagnosis was achieved by fine needle aspiration (FNA) via endoscopic ultrasound (EUS-guided FNA) as initial conventional colonoscopy failed to establish the diagnosis. Patient completed neoadjuvant chemo-radiation and her tumor was successfully resected. She is following up with oncology clinic for monitoring and further management.