The cytopathology of proliferative breast disease. Comparison with features of ductal carcinoma in situ.

Epithelial hyperplasia, a component of proliferative breast disease (PBD), is a known risk factor for the development of breast carcinoma. To determine if criteria established for tissue biopsy could be used to more precisely define cytologic criteria for diagnosis of PBD, 37 breast fine-needle aspirates with biopsy diagnoses of PBD were studied. In cases with adequate cellularity, the following findings were consistently observed: (1) three-dimensional cell clusters with outlying myoepithelial cells, swirling intralumenal masses and peripheral, slit-like, irregular sublumens (65% of cases); (2) convoluted sheets of ductal epithelium with outlying myoepithelial cells and bulbous projections tethered to the ductal lining (29%); and (3) a background of discohesive small frayed groups of ductal cells (32%). Of the 15 cases that did not meet these criteria, most were paucicellular (87%), which suggested sampling error. Other cytologic features that were observed included: moderately increased cellularity (20 cases), moderate-to-marked nuclear overlap (14 cases), minimal nuclear atypia, and few single epithelial cells. Fifteen cases of confirmed ductal carcinoma in situ were studied for comparison. In these cases, cellularity, nuclear overlap, and atypia were increased, but swirling intralumenal masses, prominent myoepithelial cells and slit-like lumens were absent. In conclusion, the features of PBD established for tissue biopsy can be applied to cytologic specimens, and may provide useful clues to the diagnosis of epithelial hyperplasia in breast fine-needle aspiration specimens.