Carcinoids: the prognostic effect of primary site histologic type variations.

Carcinoids are histologically classified as insular (A), trabecular (B) glandular (C), undifferentiated (D) or mixed. These have prognostic significance, i.e. Group 1 (most favorable, A + C); 2 (favorable, A, B, A + B); 3 (relatively unfavorable, all non A + C or A + B mixed types); and 4 (unfavorable, C, D). Midgut primaries have a better prognosis than either foregut or hindgut/cloacal primaries. Carcinoids from 114 Eastern Cooperative Oncology Group patients were studied to determine if primary site prognostic differences result from histologic prognostic group occurrence rate differences across primary sites. By primary site the following rates were observed: Foregut: 1 (0%), 2 (79.2%), 3 (12.5%), 4 (8.3%); midgut: 1 (26.7%), 2 (58.7%), 3 (6.6%), 4 (8.0%); hindgut/cloaca: 1 (0%), 2 (42.9%), 3 (42.9%), 4 (14.2%); nongut: 1 (0%), 2 (75.0%), 3 (12.5%), 4 (12.5%), p less than 0.01. The results demonstrate that primary site prognostic differences are highly dependent upon histologic prognostic group occurrence rate variations across primary sites. In addition multivariate analysis of survivorship by both histologic type (p less than 0.05) and primary site (p less than 0.05) demonstrated that each variable has independent prognostic significance.