Rare tumors of the colon and rectum: a national review.

BACKGROUND: Most literature available on rare colorectal cancer (CRC) is from case series reports. This population-based evaluation is the first comprehensive look at four rare histologic types of CRC, allowing comparisons with the more common adenocarcinoma for clinical and pathological features and survival rates.

MATERIALS AND METHODS: All patients diagnosed with carcinoid (n=2,565), malignant lymphoma (n=955), non-carcinoid neuroendocrine (n=455), squamous cell (n=437), and adenocarcinoma (n=164,638) in SEER cancer database (1991-2000) were analyzed. Evaluation of age-adjusted incidence rate, stage at presentation, and 5-year relative survival were determined for each histologic subtype.

RESULTS: All rare histologic subtypes had younger mean age than adenocarcinomas (70 years; p<0.05). Lymphoma was more common in males (65.1%; P<0.01). Incidence rates in 2000 per million were: carcinoid 10.6, lymphoma 3.5, neuroendocrine 2.0, squamous 1.9, and adenocarcinoma 496.3. The annual percent change in incidence for each rare tumor increased significantly during the 10 years (range: 3.1-9.4%, p<0.05), except squamous cell carcinoma (5.9%, p>0.05). Squamous (93.4%) and carcinoid (73.7%) tumors occurred more often in the rectum; lymphoma (79.0%), neuroendocrine (70.8%), and adenocarcinoma (70.1%) occurred more often in the colon (P<0.01). Carcinoids presented at earlier stage (localized/regional, 90.5%) more often than adenocarcinoma (80.6%; p<0.01), but squamous cell (82.1%; p=0.50), lymphoma(70.6%; p<0.01), and neuroendocrine (37.8%; p<0.01) presented at earlier stage similarly or less often than adenocarcinoma. Relative 5-year survival rate was highest for carcinoid (91.3%), and lowest for neuroendocrine tumors (21.4%).

CONCLUSION: This study provides the first population-based analysis of the epidemiology, tumor characteristics, and survival rates for rare CRC.