Abstract
There are several histologic types of breast cancer that beyond their histopathologic differences have distinct clinical characteristics. However, it is unclear how histology is related to risk of mortality particularly when differences in hormone receptor status, tumor size, and nodal status are incorporated. This study utilized a cohort of 319,463 breast cancer patients ≥30 years of age diagnosed from 1992 to 2007 identified from 17 population-based cancer registries that participate in the Surveillance Epidemiology and End Results Program. Multivariate adjusted risks of mortality associated with seven breast cancer histologic subtypes were estimated using Cox regression. Mucinous, tubular, and medullary carcinomas were associated with 31-79% lower risks of mortality compared to ductal carcinoma. Inflammatory breast cancer was associated with a 50-53% increased risk of mortality depending on age. While lobular carcinomas carried the same risk of mortality as ductal carcinoma among women 30-49 years of age, among women ≥50 years of age with node-negative disease lobular carcinoma was associated with an 11% reduced risk of mortality, but among those with node-positive disease it was associated with a 10% increased risk of mortality. This study confirms that mucinous, tubular, and medullary carcinomas have a more favorable prognosis compared to ductal carcinoma, and that inflammatory carcinoma has a poorer prognosis. Though many of these histologic subtypes are quite rare, consideration of the mortality risk associated with a given subtype may be clinically useful when making decisions regarding treatment and follow-up.