Mammary adenoid cystic carcinoma (ACC) is a rare subtype of breast cancer with a favorable prognosis. Here we report on predictors of outcome based on a detailed morphologic review and analysis of 108 mammary ACC. Sixty-four tumors (59.2%) were pure conventional ACC, 23 (21.3%) were pure basaloid ACC. Follow-up was available for 87 patients (median: 51 mo). Eighteen patients (20.7%) developed recurrence: 7 (8%) had local recurrence and 14 (16%) had distant metastasis. Two patients died of disease, 1 died of an unrelated cause, 14 were alive with disease (including 8 in palliative care), and 70 (80.5%) were alive with no evidence of disease. Of 90 patients with known lymph node (LN) status 9 (10%) had nodal involvement (all with basaloid ACC). Distant metastases in patients with predominantly basaloid ACC compared with pure conventional ACC were more common (40% vs. 7.7%) and occurred earlier (22 vs. 84 mo). The following factors were found to be predictive of recurrence-free survival: positive margin, Nottingham grade, neovascularization, basaloid component, perineural invasion, lymphovascular invasion, >30% solid growth, necrosis and LN involvement; the first 3 remained statistically significant on multivariate analysis. Factors predictive of distant disease-free survival were neovascularization, Nottingham grade, lymphovascular invasion, solid component >50%, LN involvement, basaloid component >50%, tumor necrosis, perineural invasion, and final margin. Only neovascularization remained statistically significant on multivariate analysis. Basaloid ACC is an aggressive variant of mammary ACC with more frequent nodal involvement and higher incidence of distant spread. LN staging should be performed for all mammary basaloid ACC.
*Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, University of Toronto
§Department of Anatomic Pathology, North York General Hospital
#Department of Anatomic Pathology, St. Michael’s Hospital
§§Department of Anatomic Pathology, University Health Network, Toronto
†Department of Anatomic Pathology, The Ottawa Hospital and University of Ottawa, Ottawa
‡Department of Anatomic Pathology, Cambridge Memorial Hospital, Cambridge
∥Department of Anatomic Pathology, Scarborough Health Network, Scarborough
¶Department of Anatomic Pathology, Trillium Health Partners, Mississauga
††Department of Anatomic Pathology, Juravinski Hospital and McMaster University, Hamilton, ON
**Department of Anatomic Pathology, St. Paul’s Hospital, Vancouver, BC
‡‡Department of Anatomic Pathology, Nova Scotia Health Authority and Dalhousie University, Halifax, NS, Canada
Conflicts of Interest and Source of Funding: Supported by the academic stipend of the principal investigator. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence: Elzbieta Slodkowska, MD, FRCPC, Sunnybrook Health Sciences Centre, E413-2075 Bayview Avenue, Toronto, ON, Canada M4N3M5 (e-mail: firstname.lastname@example.org).