Neuroendocrine carcinoma (NEC) is a rare disease accounting for 0.03% to 0.2% of all colorectal cancers and has been reported to occur significantly more frequently in the right-sided colon. Tumors consisting of both adenocarcinoma and NEC components or mixtures of these components have been reported. Some cases of adenocarcinoma diagnosed on H-E staining include neuroendocrine tumor components. We tested the hypothesis that distribution of endocrine tumor marker-positive cells in cancer tissue differ between right-sided and left-sided colon cancer.
The study group comprised 354 patients with stage II or III colon cancer who underwent curative resection from 2007 to 2012. Immunostaining was performed using chromogranin A (cgA), synaptophysin, and CD56 as gastrointestinal endocrine tumor markers. Cases in which positive cells were seen in some part of the cancer tissue were evaluated to be positive.
Tumors were located in the right-sided colon in 181 patients (51.1%) and the left-sided colon in 173 patients (48.8%). Immunohistochemical staining was positive for cgA in 66 patients (18.6%), positive for synaptophysin in 102 patients (28.8%), and positive for CD56 in 55 patients (15.5%). Immunohistochemical staining was positive for at least one of these markers in 118 patients (33.3%) and for all of the markers in 27 patients (7.6%). The rate of positive staining for cgA was 23.7% (43/181) in right-sided colon cancer and 13.2% (23/173) in left-sided colon cancer. The rate of positive staining for synaptophysin was 35.3% (64/181) in right-sided colon cancer and 21.9% (38/173) in left-sided colon cancer. The rate of positive staining for CD56 was 22.6% (41/181) in right-sided colon cancer and 8.0% (14/173) in left-sided colon cancer. The rates of positive staining for cgA, synaptophysin, or CD56 were significantly higher in right-sided colon cancer (p = 0.0115, p = 0.0054, and p = 0.0062).
Overall, 33.3% of patients with adenocarcinoma of the colon had endocrine tumor components in cancer tissue. The rates of positive staining for endocrine tumor markers were significantly higher in right-sided colon cancer, which may be associated with the high incidence of NEC in the right side of the colon.
Clinical trial identification
Legal entity responsible for the study
Sotaro Sadahiro, MD.
Has not received any funding.
All authors have declared no conflicts of interest.