Primary adenoid cystic carcinoma of the breast: a clinicopathological case series.

Adenoid cystic carcinoma of the breast (ACCB) is a rare special-type carcinoma, accounting for <0.1% of breast malignancies. Despite its frequent triple-negative phenotype, ACCB typically demonstrates indolent behavior and a favorable prognosis. Owing to its rarity and overlapping radiologic and histopathological features, accurate diagnosis can be challenging. We retrospectively analyzed three cases of histologically confirmed primary ACCB diagnosed at a tertiary care center. Clinical presentation, imaging findings, histomorphology, immunohistochemistry, treatment, and follow-up data were reviewed. The patients were women aged 42-58 years, all presenting with a breast lump; one case showed Paget-like nipple changes. Imaging findings varied from benign-appearing cysts to Breast Imaging Reporting and Data System (BI-RADS) category 4 lesions. Histology revealed classic biphasic morphology with tubular, cribriform, and focal solid patterns with perineural invasion noted in one. Tumor cells consistently expressed c-KIT (CD117) and myoepithelial markers (p63/S100), lacked HER2 (human epidermal growth factor receptor 2) expression, and showed variable hormone receptor status. All tumors were low-grade (grade 1), ≤2 cm, with negative sentinel lymph nodes where assessed. Surgical excision with clear margins was performed in all cases, with adjuvant radiotherapy in one patient. No recurrence or metastasis was observed on follow-up. Primary ACCB requires accurate recognition to prevent misdiagnosis and overtreatment.