Comparison of age-specific incidence rate patterns for different histopathologic types of breast carcinoma.

OBJECTIVE The age-specific incidence rate curve for breast carcinoma overall increases rapidly until age 50 years, and then continues to increase at a slower rate for older women. In this analysis, our objective was to compare age-specific incidence rate patterns for different morphologic types of breast carcinoma. MATERIALS AND METHODS We analyzed age-specific incidence rate curves by histopathologic subclassification using records from 11 standard National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registries, diagnosed during the years 1992 to 1999. Data were examined by age <50 and > or /=50 years to simulate menopause. RESULTS Age-specific incidence rate curves showed three dominant patterns: (1) Rates for infiltrating duct carcinoma of no special type (duct NST), tubular, and lobular carcinomas increased rapidly until age 50 years then rose more slowly. (2) Rates for medullary and inflammatory breast carcinomas increased rapidly until age 50 years then failed to increase. (3) Rates for papillary and mucinous carcinomas increased steadily at all ages. Rate patterns varied by estrogen receptor expression but were unaffected by SEER registry, race, nodal status, or grade. CONCLUSION Age-specific incidence rates for breast carcinomas differed by histopathologic type. Rates that failed to increase after 50 years suggested that menopause had greater impact on medullary and inflammatory carcinomas than on duct NST, tubular, and lobular carcinomas. Menopause did not seem to have any effect on papillary or mucinous carcinomas as evidenced by steadily rising rates at all ages. Future etiologic and/or prevention studies should consider the impact of age-specific risk factors and/or exposures on different histopathologic types of breast carcinomas.