Intratumoral heterogeneity in breast cancer – a real challenge for diagnosis and treatment.

We present the case of a patient with breast neoplasm which presented a particular evolution with pronounced molecular intratumoral heterogeneity proven at multiple biopsies. If in the first instance, at the primary tumor it was discovered a negative molecular HER2 luminal B pattern, in the end stage, after treatment with neoadjuvant chemotherapy, the residual tumor from the mastectomy tissue presented a luminal B profile with HER2 amplification. Under targeted anti-HER2 treatment, there was cutaneous and pleural progression, lesions that were subjected to biopsy and which revealed the presence of secondary masses with triple negative molecular pattern. [ABSTRACT FROM AUTHOR]