Microglandular adenosis of the breast: fine-needle aspiration biopsy of two cases.

Microglandular adenosis (MGA) recognizes a benign proliferative lesion of the breast that can mimic adenocarcinoma histologically. We describe the fine-needle aspiration (FNA) biopsy cytology of MGA in two female patients. Smears were characterized by sparse cellularity, and the harvest consisted of a monotonous population of medium-sized cells, with vacuolated clear cytoplasm and round and uniform nuclei with small nucleoli. Clear cells appeared isolated or clustered with spindly fibroblasts. No naked nuclei of myoepithelial origin were present in the background. The differential diagnostic considerations included several breast lesions composed of clear cells. Subsequent surgical histology of lumpectomy revealed MGA. Further studies are needed to determine whether these cytologic features permit the specific identification of MGA, but our observations show that FNA is a sensitive method in recognizing the benign nature of the lesion.