[Adenoid cystic carcinoma of the breast: clinical, histological and immunohistochemical characterization].

Background: Adenoid cystic carcinoma (ACC) of the Breast is a rare tumour (less than 1 % of all breast carcinomas). The aim of this study was to determine the clinical, histological and immunohistochemical characteristics of these tumours.

Methods: From the database of the Bergonié Institute of Bordeaux, 30 cases of ACC were identified. The clinical and histological features of these carcinomas were characterized. An immunohistochemical study was performed with the following antibodies: ER, PR, HER-2-neu, Vimentin, EGFR, P63, SMA, CK5/6, CK8/18, CK14, cKIT, MIB1, CD44 and CD24.

Results: Thirty patients were included (median age 60.7 years). The 10 axillary lymph node dissections and two sentinel lymph procedures were negative. The architecture was frequently of a mixed type (26/30) and less often solid (4/30). Among the 23 patients for whom follow up was available (median follow-up: 84 months [2-288]), there were three local recurrences and three metastatic events. The tumors with recurrence and metastasis showed more necrosis, a mitotic count greater than 4/10hpf, and in one case perineural infiltration. All the tumours were ER, PR and Her-2-neu negative. Morphological and immunophenotypical analysis disclosed in each tumor, a basaloid and a luminal cell population with divergent immunophenotypical patterns.

Conclusions: The mammary ACC is made of two cell types and is of good prognosis despite its triple negative phenotype, similar to the basal-like infiltrating carcinoma NOS. Axillary lymph node dissection is not recommended. Good local control by at least large lumpectomy with long-term follow-up is necessary.