Professor Matti Aapro [International Society of Geriatric Oncology (SIOG) and, Multinational Association of Supportive Care in Cancer (MASCC), Switzerland] discussed the heterogeneity in Her2 positive breast cancer with concentration on the role of microenvironment and tumour infiltration lymphocyte in response to anti-Her2 treatment. The gene discussed is ERBB2; the disease is cancer.