Squamous Cell Carcinoma Originating from a Dermoid Cyst Located between the Upper Rectum and Prostate: A Case Report

INTRODUCTION: Pelvic squamous cell carcinoma (SCC) originating from a dermoid cyst (DC) is extremely rare. Here, we report the first case of SCC that developed in the anterior rectal area. CASE PRESENTATION: A 46-year-old man was initially diagnosed with rectal SCC by endoscopic biopsy, and multimodal image findings demonstrated direct invasion of the urinary system. Accordingly, total pelvic exenteration with bilateral lymph node dissection was performed with robotic assistance, and the patient was discharged without severe postoperative complications. Histological assessment revealed that the cancer originated in a DC with direct invasion of the seminal vesicle. CONCLUSIONS: Pelvic DC-derived SCC is rare but possesses high malignant potential. Because of the difficulty in preoperative diagnosis, diagnostic excision may be selected if complete resection is possible. Importantly, robot-assisted surgery enables precise management and might be an optimal strategy for preventing cancer dissemination by rupture during surgery.