Objective  To compare clinicopathological characteristics and prognosis of adenoid cystic carcinoma of the breast (ACCB) and triple-negative invasive ductal carcinoma (IDC).

  Methods  From January 2004 to December 2020, 26 ACCB cases and 216 IDC cases randomly selected from Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College were assessed. Disease-free survival (DFS) and overall survival (OS) rates were evaluated using Kaplan-Meier survival curves and were compared between the ACCB and IDC groups using the Log-rank test.

  Results   The median follow-up time was 72.4 months. Four patients with ACCB developed recurrence and metastasis, mainly in the lung and liver. Age >60 years, low Ki-67 expression, nerve invasion, early TNM (Tumor Node Metastasis) stage (stage Ⅰ and Ⅱ), and negative lymph node metastasis were more common in ACCB than in IDC (P<0.05). The 5-year DFS and OS rates of patients with ACCB tended to improve compared with those of patients with IDC, although the difference was not significant. The median DFS of patients with low Ki-67 expression was significantly higher than that of those with high Ki-67 expression (χ²=4.633, P=0.031). DFS was significantly improved in patients without nerve invasion compared with those with nerve invasion (χ²=3.861, P=0.049).

  Conclusions  High Ki-67 expression and nerve invasion are risk factors for ACCB recurrence and metastasis. The clinicopathological characteristics of ACCB include low Ki-67 expression, nerve invasion, negative axillary lymph nodes metastasis, early TNM stage, and treatment method that focuses on breast-conserving surgery without adjuvant chemotherapy.