Breast fine‐needle aspiration samples reported as “proliferative breast lesion”: Clinical utility of the subcategory “proliferative breast lesion with atypia”

BACKGROUND: The fine‐needle aspiration (FNA) diagnosis of proliferative breast lesion is an indeterminate category. The aim of this correlative study was to determine whether a subcategory of “proliferative breast lesion with atypia” was achievable and whether this subcategory has management utility. METHODS: Breast FNA cases from 2000 through 2005 diagnosed as proliferative breast lesion and proliferative breast lesion with atypia were retrieved. Both cytologic and surgical slides of these cases were reviewed blindly. A cytologic diagnosis of proliferative breast lesion (without atypia) or proliferative breast lesion with atypia was used if the findings of the proliferative breast lesion did not fit a more specific category. RESULTS: Of the 3934 breast FNAs performed on palpable breast masses from January 2000 to December 2005 at the LAC + USC Medical Center, 317 (8.1%) were diagnosed cytologically as proliferative breast lesion with atypia, without atypia or without mention of atypia. There was subsequent histopathology on 201 of these cases. After the cytologic smears were reviewed, 29 cases were excluded from this study. Of the 172 remaining cases, 21 (12.2%) were found to be malignant and the remaining 151 (87.8%) were found to be benign on histology. Of the malignant cases, 90% had an FNA diagnosis of proliferative breast lesion with atypia; of the benign cases, 78% were interpreted as proliferative breast lesion without atypia. CONCLUSIONS: Proliferative breast lesion with atypia was clinically significant because it was associated with a significantly increased likelihood of malignancy compared with proliferative breast lesion without atypia. Most of the malignancies had hypocellularity or low nuclear grade on the FNA smears. Fibroadenoma accounted for most of the benign lesions in both proliferative breast lesion and proliferative breast lesion with atypia. Cancer (Cancer Cytopathol) 2009. © 2009 American Cancer Society. Because breast lesions diagnosed as proliferative breast lesion on fine‐needle aspiration FNA include significant proportions of both benign and malignant entities on histology, a subcategory of proliferative breast lesion with atypia may be helpful in dividing patients into groups needing immediate intervention and patients who can be managed more conservatively. In this study, the authors report whether a subcategory of “proliferative breast lesion with atypia” was achievable and whether this subcategory has management utility.