In 2010, Surveillance, Epidemiology, and End Results (SEER) registries began collecting human epidermal growth factor 2 (HER2) receptor status for breast cancer cases. Breast cancer subtypes are defined by joint hormone receptor (HR; estrogen receptor [ER] and progesterone receptor [PR]) and HER2 status. The SEER*Stat software includes the Breast Subtype (2010+) variable to facilitate the analysis of trends in breast cancer molecular subtypes.

Algorithm for Breast Subtype Variable

  • If the case is not Breast 2010+, value is “Recode not available”
  • If “Derived HER2 Recode (2010+)” is positive:
    • If “ER Status Recode Breast Cancer (1990+)” or “PR Status Recode Breast Cancer (1990+)” is positive*, value is Her2+/HR+
    • If “ER Status Recode Breast Cancer (1990+)” and “PR Status Recode Breast Cancer (1990+)” are both negative, value is Her2+/HR-
    • Otherwise, value is unknown or borderline*
  • If “Derived HER2 Recode (2010+)” is negative:
    • If “ER Status Recode Breast Cancer (1990+)” or “PR Status Recode Breast Cancer (1990+)” is positive*, value is Her2-/HR+
    • If “ER Status Recode Breast Cancer (1990+)” and “PR Status Recode Breast Cancer (1990+)” are both negative, value is triple negative
    • Otherwise, value is unknown or borderline*
  • All other values are unknown

*In data submissions prior to November 2020, borderline ER/PR was classified with positive.