Pathology of invasive breast disease.

Invasive breast cancers constitute a heterogeneous group of lesions. Although the most common types are ductal and lobular, this distinction is not meant to indicate the site of origin within the mammary ductal system. The main purpose of the identification of specific types of invasive breast carcinoma is to refine the prediction of likely behavior and response to treatment also offered by the other major prognostic factors, including lymph node stage, histologic grade, tumor size, and lymphovascular invasion.