Atypia in fine needle aspiration cytology of nonpalpable and palpable mammographically detected breast lesions.Acta Cytol. 1994 Jan-Feb; 38(1):9-17.AC
Widespread use of fine needle aspiration (FNA) in conjunction with mammography may lead to increased atypical or suspicious cytologic diagnoses. To assess the incidence and cytologic criteria of atypia in a mammographically screened population, we reviewed 220 FNA samples in this diagnostic category (5.8% incidence) from 3,798 FNAs performed in 1990-1991. The atypical category (134 cases) included 72 benign and 62 malignant confirmed cases. Common benign diagnoses were fibroadenoma and fibrocystic changes (33 cases, or 46%). Features responsible for an atypical diagnosis in benign cases were increased cellularity, single epithelial cells and "reactive nuclear atypia," the last defined as a finely granular, uniform chromatin pattern with small, prominent nucleoli. The suspicious category included 86 cases; only 10 cases (12%) were confirmed benign lesions, and the remainder were malignant. These benign cases included 3 fibroadenomas, 3 fibrocystic changes, 3 papillomas and 1 scar after radiotherapy. Two cases had prominent inflammation, a finding that should prompt caution. Malignant diagnoses in both categories included infiltrating and in situ cancers. A combination of limited cellularity, drying and/or bland nuclear features precluded a definitive diagnosis of cancer in many cases. For optimal management of mammographically screened patients, an acceptable "atypical" diagnostic rate should be defined for FNA. We conclude that a rate of less than 5% can be achieved by recognition of the following: (1) reactive atypia in the setting of fibrocystic and fibroadenomatous patterns, (2) significance of atypia in the setting of inflammation, and (3) improved sampling and sample preparation.