Cytologic features of ductal carcinoma in situ in fine-needle aspiration of the breast mirror the histopathologic growth pattern heterogeneity and grading.

BACKGROUND Approximately 20% of the breast carcinoma cases detected on mammography screening represent ductal carcinoma in situ (DCIS). Cytopathologists are exposed to cytologic material from DCIS when nonpalpable, mammographic lesions are aspirated during the workup of organized and opportunistic mammography screening. METHODS The material in the current study was comprised of 225 representative fine-needle aspiration cytology (FNAC) smears from histologically confirmed DCIS of the breast that were diagnosed between 1990-2003. Smears were rescreened to search for the following features: nuclear size (grading), monolayer sheets, solid and cribriform epithelial aggregates, micropapillary and true papillary structures, comedo-type necrosis, microcalcifications, myoepithelial cells, and discohesion. RESULTS There were 174 high-grade lesions (77% were Grade 3) and 51 nonhigh-grade lesions (Grades 1 and 2). The concordance between the cytologic and histologic grading was 97% in the Grade 3 lesions and 94% in the Grade 1/2 lesions. Smears from Grade 3 DCIS contained solid and/or cribriform epithelial aggregates in > 93%% of the cases, whereas smears from Grade 1/2 lesions were found to contain cribriform aggregates in 94% of the cases. Pure subtypes were virtually nonexistent. Monolayer sheets were found in 49% of nonhigh-grade DCIS and in 16% of high-grade DCIS. Myoepithelial cells were demonstrated in 51% of the nonhigh-grade DCIS lesions and 27% of the Grade 3 lesions. Microcalcifications were found on the smears from 96% of nonhigh-grade lesions and 84% of high-grade lesions. Approximately 47% of high-grade DCIS and 31% of nonhigh-grade DCIS were found to harbor a distinct single cell population. CONCLUSIONS The findings on FNAC from DCIS of the breast completely mirror the histologic heterogeneity of growth pattern subtypes. Primary cytologic grading can effectively separate the high-grade lesions from the nonhigh-grade lesions.