Cytologic findings with histologic correlation in 43 cases of mammary intraductal adenocarcinoma diagnosed by aspiration biopsy

OBJECTIVE: To review the cytologic and subsequent histologic findings in intraductal mammary adenocarcinoma (ductal adenocarcinoma in situ) (DCIS) to evaluate the role of aspiration biopsy (AB) in identifying and grading the disease. STUDY DESIGN: AB smears and tissue sections from 43 women with pure DCIS who underwent preoperative AB were reviewed. Smears were assessed for cellularity, cellular arrangement (including dissociation, nuclear size and pleomorphism), and presence of nucleoli and necrosis. RESULTS: Of the 43 cases, 22 were high grade (HG) DCIS, 7 cases were intermediate grade (IG), and 14 cases were low grade (LG). Cytologic findings of HG DCIS was as follows: high cellularity (22/22), clusters of pleomorphic cells with large nuclei and increased nuclear/cytoplasmic ratios (22/22), single cells (20/22), prominent nucleoli (22/22) and necrosis (diffuse in 15/22, focal in 7/22). All LG cases had moderately to highly cellular smears with cohesive, 3-dimensional sheets of uniform, small cells with inconspicuous nucleoli arranged around a central lumen, forming "punched-out" spaces. Single cells were prominent in 2 of 14 cases. IG DCIS showed intermediate features between LG and HG DCIS: 3-dimensional sheets with punched-out spaces, abundant single cells, moderate pleomorphism and focal necrosis. CONCLUSION: HG DCIS is easily identifiable on AB smears; however, distinction from invasive carcinoma may not be possible. The cytologic diagnosis of LG DCIS is difficult, and 50% of our cases were called atypical on AB. Recognition of cohesive cellular arrangements with crowding and punched-out spaces is crucial as single cells and prominent atypia are often lacking.