Adenoid cystic carcinoma of the breast: a tumour commonly devoid of oestrogen receptors and related proteins.

Aim: Adenoid cystic carcinoma (ACC) of the breast is an uncommon well-differentiated tumour with good prognosis, and sometimes difficult to distinguish from in-situ and invasive cribriform carcinoma (ICC) which are relatively more common. Recently, we encountered a case of ACC that proved to be totally oestrogen receptor (ER) negative by immunohistochemistry. We investigated the possibility that this may be a consistent feature that can help in differentiating ACC from ICC which are usually ER positive.

Methods And Results: The immunoperoxidase technique was used to study the expression of ER and other related proteins in six cases of ACC and two cases of ICC. All ACC cases were negative for oestrogen (ER) and progesterone (PgR) receptors whereas the two ICC were strongly positive for ER and showed a variable degree of PgR positivity. In addition, ACC cases were pS2 negative and showed minimal expression of prolactin receptors (PrlR), while the two ICC showed widespread and strong staining for pS2 and PrlR. The percentages of cells staining positively for Ki67 and p27 were generally lower in ACC than in ICC. Both tumour types were c-erbB-2 negative, but p53 was weakly to moderately positive.

Conclusions: The findings suggest that a negative immunoperoxidase staining for ER would confirm the diagnosis of ACC in contrast to the positive staining which is always seen in ICC. The findings also raise the issue of the presence of a specific class of ER negative breast carcinomas which are negative not because of poor differentiation, but because of their derivation from, or differentiation along, an ER negative cell lineage.