Primary submucosal squamous cell carcinoma of the rectum diagnosed by endoscopic ultrasound: Case report and literature review

Primary colorectal squamous cell carcinoma (SCC) is one of the very rare malignancies of the gastrointestinal tract. The diagnosis cannot be made before ruling out other common primary sites. Using the endoscopic ultrasound (EUS) technique to get a tissue biopsy for submucosal tumors has not been demonstrated as the best diagnostic approach in the literature. Surgery is the gold standard treatment with arising evidence of good efficacy following conventional chemoradiation therapy. A 49-year-old male presented with rectal discomfort. Sigmoidoscopy revealed multiple submucosal masses in the rectosigmoid colon. Mucosal biopsies showed nonspecific inflammation. Subsequently, an EUS with fine needle biopsy was done and established the diagnosis of rectal SCC. There were no other primary sites noticed in the extensive evaluation. The patient chose to be treated only with chemoradiation without surgery. At the time of writing this report he had no evidence of recurrence achieving 2.5 years of survival. EUS is an emerging excellent approach to diagnose submucosal colorectal SCC. This case will add supportive evidence of having a complete response following combining treatment with squamous cell directed chemotherapy and external beam radiotherapy without preceded surgery.