Beyond its Rarity: A 10-year Study on Primary Adenoid Cystic Carcinoma of the Breast from a Tertiary Care Center

Adenoid cystic carcinoma (AdCC) of the breast is a rare malignancy (~0.1%), affecting women in their 50s-60s. It presents as a palpable mass with tubular, cribriform, and solid patterns and shows biphasic differentiation. C-Kit expression supports diagnosis. Despite its triple-negative status, AdCC has a favorable prognosis, except in solid-basaloid variants.

This retrospective study was conducted in the Department of Histopathology, Apollo Cancer Center, Chennai, and included all cases of primary breast AdCC diagnosed between January 2014 and December 2024.

Twelve female patients were included, with a mean age of 55.5 years. All presented with a breast lump; right and left sides were equally involved, with the upper outer quadrant being the most common site (70%). Surgical management included wide local excision (WLE) (45.45%), modified radical mastectomy (36.36%), total mastectomy (9.09%), and chemotherapy/immunotherapy in one patient (9.09%). Multifocality was seen in 16.66% (2/12). Mean tumor size was 2.66 cm, and pT2 stage was most frequent (57.14%). One case showed local recurrence post-WLE; another developed lung metastasis. Histologically, 75% showed all three patterns with solid areas ranging from 10% to 90%. Perineural invasion was seen in 58.33% (7/12) and lymphovascular invasion in 16.66% (2/12). Most tumors were Nottingham Grade 2 (83.33%). All were progesterone receptor and HER2/neu negative; estrogen receptor positivity was seen in two cases. C-Kit was positive in all tested cases. Ki-67 index ranged from 6% to 80%.

Breast AdCC shows favorable prognosis. Most cases were pT2, stage IIA, with rare recurrence or metastasis.