Biological heterogeneity of primary and metastatic brain tumor in breast cancer patients

Purpose: to evaluate the frequency of discordance of receptor status and HER2 status in primary and metastatic brain tumor in patients with breast cancer. Material and methods. The study included 18 patients whose brain metastases from breast cancer were treated surgically. An immunohistochemical assay of tumoral samples was performed to assess the expression of ER, PR, HER2. The results obtained were compared in pairs with samples from primary tumors. Results. The receptor status of the primary tumor and brain metastasis was constant in 50% of patients, while discordance in HR status was detected in 44% of cases. The rarest receptor conversions were the acquisition of HER 2+ status at 6% (n=1) and the loss of HER 2+ status at 11 % (n=2). 67% of patients with HR+ primary breast tumors, receiving adjuvant anti-estrogen therapy lost expression of the target receptor in brain metastases. Conclusion. In half of the tumor pairs under study we detected discordance in at least one of the indicators (ER, PR, HER2) of tumor biological heterogeneity. Loss of HR+ status in metastatic tumor was observed more often than other morphological transformations.