Assessment of tumor heterogeneity, as evidenced by gene expression profiles, pathway activation, and gene copy number, in patients with multifocal invasive lobular breast tumors [gene copy number]

Invasive lobular carcinoma (ILC) comprises approximately ~10-20% of breast cancers. In general, multifocal/multicentric (MF/MC) breast cancer has been associated with an increased rate of regional lymph node metastases. Tumor heterogeneity between foci represents a largely unstudied source of genomic variation in those rare patients with MF/MC ILC. We characterized gene copy number in 2 or more foci from 11 patients with MF/MC ILC (all ER+, HER2-) and adjacent normal tissue. RNA was extracted from 3x1.5mm cores from all foci. Gene copy number was measured using the Nanostring Cancer CNV panel, version 1. Copy number was compared between multiple foci within each patient.