Expression of GCDFP-15 and AR decreases in larger or node-positive apocrine carcinomas of the breast

Aims: Apocrine carcinoma of the breast is typically, though not always, positive for gross cystic disease fluid protein-15 (GCDFP-15). In order to clarify the clinical significance of GCDFP-15 in apocrine carcinomas, GCDFP-15 expression was examined in apocrine carcinomas of different stages and compared with clinicopathological factors. Apocrine lesions reportedly exhibit an unusual immunohistochemical status, expressing androgen receptors (AR) instead of oestrogen receptors (ER), progesterone receptors (PR), or bcl-2. Their expression was also examined. Methods and results: Fifty-two apocrine carcinomas were examined immunohistochemically. Thirty-nine (75%) and 29 (56%) were positive for GCDFP-15 and AR, respectively. GCDFP-15 positivity was significantly lower in infiltrating carcinomas than intraductal carcinomas (P = 0.0111). In infiltrating carcinomas, GCDFP-15 positivity was significantly low in tumours >= 15 mm (P = 0.0005) and node-positive tumours (P = 0.0004). Similar phenomena were observed for AR. Rare cases were positive for ER (3.8%), PR (5.8%), and bcl-2 (1.9%). Conclusions: GCDFP-15 positivity is transient and should not be considered a definitive marker of apocrine carcinomas. Cases which have apocrine features but lack GCDFP-15 expression should rather be considered as advanced apocrine carcinomas. ER/PR/bcl-2 negativity will sometimes be helpful to confirm the diagnosis of apocrine carcinoma, because it is more consistent than GCDFP-15/AR positivity.