Diagnostic challenge of lobular carcinoma on aspiration cytology

Lobular carcinomas are among the most difficult to type correctly on aspiration cytology. The inherent cytologic traits such as small size and bland appearance of cells in scanty aspirates may lead to false-negative diagnoses. Due to the low incidence of this form of breast carcinoma, there are few studies solely on lobular carcinoma, and the cytomorphologic features are not well defined. To delineate the cytomorphologic features and to assess their utility in correctly typing an aspirate as lobular carcinoma, we undertook a retrospective review of fine-needle aspirates from 31 cases of lobular carcinoma. The cytologic features of monomorphic cells, with scant cytoplasm, central vesicular nuclei, and inconspicuous nucleoli were found most helpful in correct typing of the cases. Intracytoplasmic vacuoles, nuclear grooves, and "Indian-file" arrangement of cells were corroborating features. We postulate that a combination of cytologic features makes the diagnostic delineation of lobular carcinomas possible on aspiration cytology.