Discordant ERBB2 Status and Genome Wide DNA Copy Number Alterations in Breast Cancer and Synchronous Lymph Node Metastasis: A Case Report and Literature Review.

Erb-b2 receptor tyrosine kinase 2 (ERBB2) is a biomarker in the management of breast cancer (BC). Changes of ERBB2 status in primary and synchronous metastasis have been reported in approximately 5% of BC. Here we describe a 55-years-old female with a history of left-side BC and again diagnosed in 2019 with right-side BC tested ER-, PR-, ERBB2+ in breast tissue and triple negative in right axillary lymph node. The right BC and lymph node metastasis samples were tested by chromosomal microarray (CMA); the BC sample harbored more DNA copy number alterations than the lymph node specimen, suggesting that the lymph node metastasis was not directly originating from a dominant tumor clone in the right BC. This case highlights discordant ERBB2 status that can benefit from assessment of ERBB2 in both primary and metastatic specimens. This case also demonstrates the value of using CMA to help understand the clonal evolution of breast cancer metastasis especially when there are discordant biomarker results between primary and metastatic lesions.