Hormone-receptor status definition in invasive ductal carcinoma, no special type
Hormone-receptor (HR) status for invasive breast cancer is defined by estrogen receptor (ER) and progesterone receptor (PgR) results from validated immunohistochemistry (IHC), rather than by histologic type (including invasive ductal carcinoma, no special type). [1]
Dependence on pathology testing
ER testing by validated IHC is recommended to predict benefit from endocrine therapy. [1] PgR testing is performed using similar principles and is used primarily for prognostic purposes in the setting of an ER-positive cancer. [1]
ER interpretation categories
An invasive breast cancer is considered ER positive when 1% to 100% of tumor nuclei are positive. [1] ER low positive is a reporting category for cases with 1% to 10% of tumor nuclei positive, with a recommended comment. [1] A tumor is considered ER negative when <1% (or 0%) of tumor cell nuclei are immunoreactive. [1]
Practical implication for “invasive ductal carcinoma, no special type”
“Invasive ductal carcinoma, no special type” describes a histologic diagnosis and does not by itself specify HR status. [1] Therefore, HR status is determined by the reported ER and PgR IHC results for the specific tumor specimen. [1]
Information needed to state HR status for an individual case
The pathology report ER result (including the percentage of positive tumor nuclei and whether it is reported as ER low positive) is required to assign ER status. [1] The pathology report PgR IHC result is required to assign PgR status. [1]