Stercoral Rectal Ulceration or a Missed Diagnosis of Rectal Carcinoma: Primary Signet Ring Cell Carcinoma of the Rectum Presenting as Fecal Incontinence in an Elderly Female

Abstract

Primary signet ring cell carcinoma of the rectum is a rare entity accounting for approximately 1% of all colorectal carcinomas. It arises more frequently in the stomach and is associated with younger patient population and advanced stage on presentation. Constipation is the main factor for development of stercoral ulcer which originates as a result of pressure necrosis of the colorectal mucosa. We describe an atypical case of an elderly female with primary signet ring cell carcinoma of the rectum presenting with fecal incontinence. A 68-year old woman presented with worsening fecal incontinence and hematochezia. Rectal exam revealed a firm tissue in the lateral anal canal. The endoscopic evaluation showed a friable partially necrotic ulcerated lesion at the anorectal junction extending at least 5 cm proximally. The histologic examination of the lesion was diagnostic for a primary signet ring cell carcinoma of the rectum (positive for CK 7 and CK 20 and negative for CDX-2). Computed tomography scan of the abdomen/pelvis revealed rectal wall thickening and MRI of the pelvis demonstrated a low rectal tumor with perianal involvement, clinical T3N2 with an enlarged right external iliac lymph node. Patient received chemo-radiation and later underwent laparotomy with abdominal perineal resection and an end colostomy was performed. Patient had good clinical progress and was discharged to a skilled nursing facility. Patient had a colonoscopy done three years prior for similar symptoms and was noted to have stercoral ulcerations in the rectum but rectal biopsies at that time were unremarkable. This case highlights the following important points. Ulcers particularly stercoral ulcers may herald a concealed malignant disease, hence surveillance colonoscopy/sigmoidoscopy should be considered. Also, the diagnosis of primary rectal signet ring cell carcinoma should be investigated in the elderly presenting with the complaint of fecal incontinence.1670_A Figure 1. Colonoscopy revealed a friable, necrotic and ulcerated rectal lesion.1670_B Figure 2. CT scan demonstrated rectal wall thickening.