Association between breast cancer laterality and tumor location, United States, 1994-1998.

Objective: Cancer is more likely to be diagnosed in the left breast than the right, but the reasons are undetermined. Left-sided predominance has not been evaluated for some demographic groups or by tumor location.

Methods: Laterality was analyzed among 419,935 incident unilateral breast cancers from 26 population-based cancer registries covering 40% of the US population.

Variation in breast cancer counts using SEER and IARC multiple primary coding rules.

Objective: To determine breast cancer case counts, on a given data set, using both Surveillance, Epidemiology, and End Results (SEER) program and International Agency for Research on Cancer (IARC) multiple primary coding rules and to describe differences, if any, by age at diagnosis, histology, stage at diagnosis, laterality, and grade.

Methods: SEER and IARC multiple primary coding rules were applied to a dataset provided by the North American Association of Central Cancer Registries. Only registries whose data met high quality data standards for the time period studied (1994-1998) and whose permission was obtained were included.