Rare Cases of Synchronous Colon Adenocarcinoma and Rectal Carcinoid Tumor

Abstract

Colorectal cancer is the fourth and the third most common cancer in men and women, respectively, worldwide. Carcinoid of the rectum is the second most common site for gastrointestinal neuroendocrine tumors (NET). Concurrent colon adenocarcinoma and rectal carcinoid has not been reported. Here, we report two rare cases of synchronous colon adenocarcinoma and rectal carcinoid. Case Presentations Case #1 A 40 year old white male presented with hematochezia and abdominal pain. A CT of the abdomen and pelvis revealed focal segment of the sigmoid colon with thick wall, surrounding fat stranding and prominent lymph nodes. Follow up colonoscopy revealed a friable, ulcerated mass with biopsies revealing moderately differentiated adenocarcinoma. A rectal polyp was resected with biopsy revealing well-differentiated neuroendocrine carcinoid tumor. Computerized scan of the chest was negative for any metastasis. Patient underwent laparoscopic sigmoidectomy. Pathologic examination revealed moderately differentiated adenocarcinoma invading the peri-colonic fat. Adjuvant chemotherapy was started 4 weeks post operatively. Case #2 A 70 year old man with history of stage III adenocarcinoma of the colon was also found to have a rectal polyp consistent with carcinoid. The patient underwent trans anal resection and received adjuvant chemotherapy. Recent follow up colonoscopy was negative for malignancy. Discussion: NETs are rare and only represent 0.5% of all newly diagnosed cancer. Rectal carcinoids accounts for only 1-2% of all rectal tumors. We report cases of synchronous colorectal adenocarcinoma and rectal carcinoid. There was one case report of synchronous well-differentiated adenocarcinoma of the sigmoid colon and malignant ileal carcinoid tumor. While rectal carcinoids are typically nonfunctioning and asymptomatic, their presence should raise awareness of a potential synchronous cancer as observed in our cases. Conclusion: Synchronous colon adenocarcinoma and rectal carcinoid are rare but can be diagnosed with colonoscopy. The detection of rectal carcinoid necessitates thorough evaluation of the remainder of the colon for cancer so that timely treatment can be carried out.