Benefits of using the cell block method to determine the discordance of the HR/HER2 expression in patients with metastatic breast cancer

The discordance of the hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) expressions between primary cancer and metastatic lesions is an important issue when selecting the optimal treatments for patients with metastatic breast cancer. A rebiopsy for the metastatic cancer is recommended before selecting the treatment; however, it is not easy to take a tissue sample for all metastatic lesions. Fine needle aspiration cytology (FNA) for regional lymph nodes and aspiration for pleural effusions or ascites are less invasive procedures to obtain the necessary samples to examine the HR/HER2 expression. These cytologic materials are able to be stained as a tissue sample using the cell block method. We examined the HR/HER2 expression of 20 patients with breast cancer (8 with synchronous metastases and 12 with metachronous metastases) using the cell block method. Among 8 patients with synchronous metastases, 7 patients with axillary lymph node (LN) metastasis were examined by fine needle aspiration (FNA), and one patient with pleural metastases was analyzed for the aspirated fluid. While in 12 patients with metachronous metastases, 7 patients were examined for their pleural effusion, 3 patients were examined for regional lymph node metastases, and 1 patient were examined for aspirated ascites. We compared the HR/HER expression between primary cancer and metastatic lesion in 17 patients (5 cases of 8 synchronous metastases, and all of 12 metachronous metastases). Discordance of HR was seen in 4 of 17 patients (24 %). Three cases with axillary LN metastasis (2 cases with synchronous metastases and one with metachronous metastasis) showed negative change of ER. Negative change of HER2 expression was seen in one patient with ascites caused by peritoneal dissemination. Cytology materials are easily obtained by FNA for LN metastases and aspiration for malignant effusions and analyzed for HR/HER2 expression using cell block method. We should take advantage of cell block analysis to determine the discordance of the HR/HER2 expression to select the optimal treatment for metastatic breast cancer.