'Atypical' and 'suspicious' diagnoses in breast aspiration cytology

Background: In 1996, the National Cancer Institute (NCI) recommended five categories for the diagnosis of breast aspiration cytology: benign, atypical, suspicious, malignant, and unsatisfactory. The authors evaluated the usefulness of separating inconclusive diagnoses into the aforementioned atypical and suspicious categories. The current study examined the correlation between cytologic and histologic findings made in breast aspiration cytology specimens that were categorized in accordance with these NCI guidelines.

Methods: From 1992 to 2000, 7727 breast aspirations were performed at the University of Miami/Jackson Memorial Medical Center (Miami, FL). Aspirates were classified using criteria similar to the NCI recommendations. Four hundred eighty-nine aspirates (6%) were classified as being cytologically 'atypical' or 'suspicious'. Of those, 225 'atypical' aspirates and 162 'suspicious' aspirates had available histologic follow-up data and were included in the study.

Results: Among the 'atypical' aspirates, 118 (52%) yielded malignant findings on histologic evaluation. Infiltrating ductal carcinoma (n = 87; 74%) was the most common malignant diagnosis, followed by infiltrating lobular carcinoma (n = 12; 10%). Among 'suspicious' aspirates, 135 (83%) yielded malignant findings on histologic analysis. The most common benign diagnosis in both 'atypical' and 'suspicious' aspirates was proliferative fibrocystic changes with or without atypia, followed by fibroadenoma.

Conclusions: Most aspirates that yielded suspicious findings on cytologic examination proved to be malignant, as did > 50% of aspirates that yielded atypical findings. Infiltrating lobular carcinoma commonly was underdiagnosed as being atypical on cytologic examination. Benign lesions with atypical or suspicious cytologic diagnoses included certain cases of atypical ductal hyperplasia. The authors concluded that the distinction between the atypical and suspicious categories, as recommended by the NCI, is not warranted. Therefore, they suggest the use of a single term, such as 'equivocal', to describe inconclusive diagnoses on breast fine-needle aspiration cytology.