Human epidermal growth factor receptor 2 protein expression between primary breast cancer and paired asynchronous local-regional recurrences.

Knowledge concerning concordance of epidermal growth factor receptor 2 (HER2) expression between primary breast cancers and asynchronous local-regional recurrences is sparse. Receptor characteristics could be altered with time and may be affected by anticancer treatment. It remains uncertain whether recurrences have the identical or similar HER2 receptor expression pattern as the primary breast cancer. The aim of the present study was to evaluate whether HER2 is stable during the process of recurrence. Expression of HER2 was investigated immunohistochemically in paired samples of primary breast cancers and corresponding asynchronous local-regional recurrences (n=35). HER2 expression was scored as 0, 1+, 2+ or 3+. HER2 overexpression (2+ or 3+) was found in 48.57% (17/35) of the primary breast cancers and 45.71% (16/35) of the corresponding local-regional recurrences. A concordance of HER2 overexpression between the primary lesions and matching regional recurrences was observed in 85.71% of the breast cancer cases. Five out of the 35 paired samples (14.28%) were discordant. Only 3 patients who had 2+ HER2 expression in the primary tumors showed HER2 down-regulation (0 or 1+) in the recurrences, while the HER2 score in 2 patients changed oppositely. Moreover, all of the cases with 3+ HER2 staining in the primary lesions retained HER2 overexpression in the recurrences. The HER2 is commonly expressed in breast cancer, and its expression in the primary tumors and the corresponding recurrences was concordant in the majority of the cases. As the receptor expression may lose or gain in recurrences at a probability of approximately 10%, assessment of the receptor status in recurrences is still encouraged.