Rare breast cancer: 933 adenoid cystic carcinomas from the national cancer data base

Background: Adenoid cystic carcinoma (ACC) is a rare subtype of breast malignancy. Methods: Patients with ACC and infiltrating ductal carcinoma (IDC) reported to the National Cancer Data Base from 1998 to 2008 were reviewed for patient age, ethnicity, tumor size, nodal status, American Joint Committee on Cancer TNM Stage, tumor grade, initial treatment, hormone receptor status (for patients from 2004 to 2008), and survival (for patients from 1998 to 2003). Results: A total of 933 patients with ACC and 729,938 with IDC were identified. No differences were found for incidence by race/ethnicity (p = 0.97). The group with ACC was older (median 60 vs. 58 years), had larger tumors (median 18 vs. 16 mm), had more grade 1 tumors (46 vs. 18 %), was less likely to undergo axillary lymph node evaluation (75.9 vs. 96.3 %), had fewer node-positive patients (5.1 vs. 35.5 %), had fewer estrogen receptor-positive tumors (15.4 vs. 75.6 %), had fewer progesterone receptor-positive tumors (13.3 vs. 65.2 %), and underwent breast-conserving surgery more often (69.8 vs. 59.8 %). Chemotherapy was provided less often for ACC (11.3 vs. 46.4 %), as was hormone therapy (9.1 vs. 42.3 %). All of these differences were statistically significant (p < 0.0001). With a median follow-up of 65.7 months (ACC) and 64.9 months (IDC), 5-year overall survival (OS) was 88 % for ACC vs. 84 % for IDC (p = 0.02). Grade 1 OS (ACC, 91 % vs. IDC, 92 %; p = 0.50) and stage I OS (ACC, 90 % vs. IDC, 91 %; p = 0.93) were equal. Conclusions: Compared with IDC, ACC has different characteristics (lower grade, hormone receptor negative, node negative), is treated differently (less axillary surgery, fewer mastectomies, less chemotherapy, less hormone therapy), and has an improved prognosis, with 88 % 5-year survival.