Interval Squamous Cell Carcinoma of the Rectum.

Squamous cell carcinoma (SCC) of the rectum is a rare clinical entity with an incidence rate of 0.1-0.25% per 1,000 cases. Though its etiology and pathogenesis remains unclear, it has been associated with chronic inflammation and infections. Herein, we report a case of an 82-year-old female who presented with a 2-month history of worsening abdominal pain, hematochezia, and bilateral inguinal lymphadenopathy with right-sided purulent discharge. Two years prior, she had had an unremarkable screening colonoscopy which met all quality indicators. Abdominal CT scan showed an irregular rectal mass with bulky pelvic and retroperitoneal adenopathy. Colonoscopy revealed one large circumferential nonobstructing lesion in the rectum. Endoscopic ultrasound confirmed its origin from the rectal wall with an enlarged perirectal lymph node. Cold biopsy followed by histopathology revealed SCC of the rectum.