Adenoid cystic carcinoma of the breast: A case report and clues for its differential diagnosis

Purpose: Adenoid cystic carcinoma (ACC) of the breast is an uncommon, well-differentiated tumor with excellent prognosis. Sometimes it is difficult to distinguish ACC from in situ and invasive cribriform carcinoma (ICC), which is relatively more common. In this Article we tried to find out histopathological clues for differential diagnosis between ACC and ICC, based on one case with ACC of the breast and 10 cases of ICC. Material and methods: All ACC and ICC cases were stained with haematoxylin-eosin (H;E), and PAS/alcian blue. An immunoperoxidase technique was used to study the expression of oestrogen receptor (ER), progesterone receptor (PR), p53, c-erbB-2 (Her 2/neu) and Ki-67 index. The ACC case was stained additionally for cytokeratin (CK), S-100, smooth muscle actin (SMA), and collagen type IV. Results: The ACC case was negative for ER, PR, p53 and c-erbB-2. Ki-67 index of this tumor was 3%. The myoepithelial cells of the ACC were stained weakly for S-100 and SMA. The epithelial cells were positive for CK. The intraluminal basement membrane-like material was positive for type IV collagen. In ICC cases the ER positivity was 40%, PR 90%, p53 60%, c-erbB-2 70%, and the mean value of Ki-67 12.5%. Conclusion: ACC of the breast is a rare tumor and must be correctly diagnosed. Although its histopathological similarity with ICC may cause difficulties in diagnosis, the ER and PR negativity, and the biphasic cellularity are helpful and reliable findings for the differential diagnosis