Fine-needle aspiration biopsy of adenoid cystic carcinoma of the breast: a case report.

We describe the cytologic findings of a fine-needle aspiration (FNA) breast lesion with a typical histology for adenoid cystic carcinoma. The aspirate yielded highly cellular smears with a monomorphic population of small, slightly atypical cells, arranged in multilayered groups with abundant fine intercellular metachromatic substance between cell groups. There were also fragments of fibrillar stroma in close relation to epithelial cells. The diagnosis based on the FNA material was suspicious of malignancy. The cytomorphology in this case presented a difficult differential diagnosis with pleomorphic adenoma. Features indicative of adenoid cystic carcinoma were nuclear cell hyperchromasia, the presence of small nucleoli, and scant, poorly defined, or absent cytoplasms. Differential diagnosis of breast adenoid cystic carcinoma with other entities will also be discussed.