Aim: Cytological diagnosis of mammary papillary lesions is difficult. We reviewed the previous cytology diagnosis of 23 papillomas and 11 papillary carcinomas and specific cytological features that may assist in differentiating these entities.
Methods: The cytology preparations were reviewed for (i) overall cellularity; (ii) epithelial cell ball devoid of fibrovascular cores; (iii) single cells; (iv) papillary fragments and their morphology.
Results: The overall diagnostic accuracy was 59%, atypical rate was 24%, and the error (combined false positive and negative) rate was 17%. For overall cellularity, six, 14 and three cases of papillomas and six, three and two cases of papillary carcinoma showed low, moderate to high cellularity respectively. Cell balls were present in mild to moderate number in 20 papillomas and ten papillary carcinomas. The background single cells were absent, present in low or moderate to high numbers in seven, ten and six papillomas and three, three and five papillary carcinomas respectively. Papillary fragments were absent, present in small, moderate or large quantities in nine, four, eight and two papillomas and six, three, one and one papillary carcinomas respectively. There is no demonstrable quantitative difference between papilloma and papillary carcinoma for all these parameters. Qualitatively, the cell balls and single cells showed higher degree of atypia in papillary carcinoma, and the papillary fragments were more elaborate and slender.
Summary: Cytological diagnosis of papillary lesions shows significant error rate with overlapping features. Cellular atypia and fragments with long and slender papillae with ramifying edges favours papillary carcinoma.