Lactating adenoma--cytomorphologic study with review of literature.

Lactating adenoma is an uncommon well-differentiated benign tumor of secretory mammary epithelium that occurs in pregnant and lactating women. Three percent of all breast cancers are diagnosed during pregnancy and need to be differentiated from other breast masses occurring in pregnancy and lactational states. Its origin, though controversial, is believed to be de novo or a variant of pre-existing tubular adenoma or fibroadenoma, that reflects the morphologic changes resulting from the physiologic state of pregnancy. Four pregnant/lactating women presenting with solitary breast masses were aspirated. Spontaneous regression of the mass was observed in two of the four cases, one underwent excision biopsy and one case was lost to follow up. All four cases were diagnosed as lactating adenoma on fine needle aspiration cytology. Cytomorphologic features included cellular aspirates comprising of epithelial cells, scattered and in small groups. The acinar cells had foamy to vacuolated cytoplasm. The nucleus had prominent nucleoli. Background showed abundant foamy material. Biopsy confirmed lactating adenoma in one of the cases. Lactating adenoma needs to be differentiated from other breast masses, including carcinoma, in pregnant or lactating women. Sonographic studies are not diagnostic and surgical biopsies are not recommended as a majority of the lesions are known to regress spontaneously.