Analysis of the Incidence and Clinical Features of Colorectal Nonadenocarcinoma in Korea: A National Cancer Registry-Based Study

Purpose: Although most colorectal malignancies are adenocarcinomas from mucosa, various types of malignant and benign tumors can develop. Due to extremely low incidence, little research has been conducted. The purpose was to assess incidence and compare it according to demographic factors.Methods: Data from the Korea National Cancer Registry from 2007 to 2016 were used. The crude incidence, age-standard incidence rate (ASR) of colorectal nonadenocarcinomas were calculated.Results: Over 11 years, there were 267,142 patients with colorectal malignancies. The patients of 14,495 (5.43%) were diagnosed with nonadenocarcinoma. The ASR was 2.52 per 100,000 in men and 1.56 in women. Lesions were classified according to histologic categories; neuroendocrine tumor (NET) was the most common malignancy (10,919 [75.33%]). Nonadenocarcinoma was the most common in 40s and 50s (40 to 49 years, 3,530 [24.35%]; 50 to 59 years, 3,991 [27.53%]). Lymphoma was high (54.46%) in patients in teenagers. Proportion of NET decreased with age and that of carcinoma increased with age. Carcinoma, sarcoma, and lymphoma were more common among men and melanoma was more common among women. The most common site was the rectum (11,066 [76.34%]). Lymphoma occurred more frequently in proximal colon. Melanoma, gastrointestinal stromal tumor, and NET occurred mostly in rectum. A total of 10,155 patients (70.06%) were classified as having localized disease.Conclusion: This study is meaningful as it is the first study to examine incidence of colorectal nonadenocarcinoma. Differences in incidence of different lesions based on demographic factors were identified. This study will play a role in cancer prevention and diagnosis projects.