[Comparison of HER2 gene status between primary breast cancer and synchronous axillary lymph node metastasis]

To investigate the discordant rate of HER2 gene status between primary breast cancer and synchronous axillary lymph node metastasis.

One hundred and fifty cases of primary breast cancer with corresponding synchronous lymph node metastases were collected, including 50 cases of HER2 FISH positive, 50 cases of HER2 FISH negative and 50 cases of HER2 FISH equivocal primary tumors, at Peking Union Medical College Hospital between May 2012 and June 2015. The HER2 gene status in lymph node metastatic tumors was analyzed by FISH, and the discordance of HER2 gene status was identified between primary and metastatic tumors.

The incidence of discordant HER2 gene status between primary breast cancer and synchronous lymph node metastasis was 20.67%(31/150). Forty-four FISH positive, 3 FISH equivocal and 3 FISH negative cases were found in the first group of 50 patients with HER2 positive results in primary tumor. Forty seven FISH negative, 3 FISH equivocal cases were discovered in the second group of 50 patients with HER2 negative results in primary tumor. Four FISH positive, 18 FISH negative and 28 equivocal cases were observed in the third group of 50 patients with HER2 equivocal results in primary tumor. The discordance of HER2 gene status between primary tumor and lymph node metastasis in the third group of patients was significantly higher than the other two groups (P<0.05).

Significant discordance of HER2 gene status between the primary and lymph node metastatic tumors exists. Patients with lymph node metastasis, simultaneous testing of HER2 status may be performed in both primary breast tumor and its lymph node metastasis. HER2 status of nodal metastatic lesion may be more relevant for guiding anti-HER2 target therapy.