A population-based study of colorectal cancer histology in the United States, 1998-2001.

BACKGROUND: Histology is an important factor in the etiology, treatment, and prognosis of cancer. The purpose of this study was to descriptively characterize colorectal cancer (CRC) histology in the United States population.
METHODS: Data from cancer registries in the National Program of Cancer Registries (NPCR) or Surveillance, Epidemiology and End Results (SEER) program, representing 88% of the U.S. population, were used in the study. The analysis included 522,630 microscopically confirmed CRC cases diagnosed from 1998-2001.
RESULTS: About 96% of CRCs were adenocarcinomas, approximately 2% were other specified carcinomas (including carcinoid tumors), about 0.4% were epidermoid carcinomas, and about 0.08% were sarcomas. The proportion of epidermoid carcinomas, mucin-producing carcinomas, and carcinoid tumors was greater among females. Several histologic patterns with regard to race and ethnicity existed, including a higher percentage of carcinoid tumors among most non-white populations. With respect to age, higher percentages of sarcomas, mucin-producing adenocarcinomas, signet ring cell tumors, and carcinoid tumors were found in individuals under age 40. Overall, adenocarcinomas were more likely to be diagnosed at regional stages with moderate differentiation. Compared with other adenocarcinomas, signet ring cell tumors were more often poorly differentiated and were at distant stage at diagnosis. Carcinoid tumors and sarcomas were mainly poorly differentiated and were at localized stage at diagnosis. Small cell carcinomas were more likely undifferentiated and were at distant stage at diagnosis.
CONCLUSIONS: To date, this is the largest population-based study to analyze CRC histology in the United States. Distinct demographic and clinical patterns associated with different histologies may be helpful for future epidemiologic, laboratory, and clinical studies.