Adenoid Cystic Carcinoma of the Breast: Clinical and Radiological Findings.

Background/Objectives: Breast adenoid cystic carcinoma (ACC) is a rare tumor with limited data on imaging features and treatment response. This study investigated the clinical and radiological characteristics of ACC of the breast. Methods: Patients with ACC who underwent surgery at our institution between February 2010 and December 2023 were included. Clinical characteristics, biopsy and surgical pathology findings, and follow-up outcomes were reviewed. Preoperative mammography, ultrasound (US), and MRI findings were analyzed. Results: Twenty-eight women (mean age, 57 ± 8 years) were identified. Half presented with palpable masses, and the remainder were detected on screening. Percutaneous biopsy was performed in 27 patients, correctly diagnosing ACC in 18 (66.7%), whereas 9 (33.3%) were misdiagnosed as having invasive ductal carcinoma. The mean tumor size was 2.9 cm (range, 0.9-8 cm), with axillary metastasis in two women (7.1%). Most tumors were triple-negative (78.6%), while six showed low estrogen-receptor positivity (<10%). Ki-67 was <20% in 64.3%, with no high values (≥75%). Three patients received neoadjuvant chemotherapy, with two non-responders. No recurrences occurred during a median follow-up of 51 months. Imaging revealed masses on mammography (85.2%), US (92.9%), and MRI (92.3%), with calcifications in two cases. Most lesions were highly suspicious (BI-RADS 4C or 5) and showed increased vascularity in 92.3% on Doppler US. Conclusions: Breast ACC typically presents as a hypervascular, highly suspicious mass. Despite frequent triple-negative profiles, it shows low proliferation, poor response to chemotherapy, and favorable prognosis.