Adenocarcinoma in situ with a small cell (endometrioid) pattern in cervical smears

BACKGROUND: Papanicolaou smears have been less effective in preventing cervical adenocarcinoma than in preventing squamous carcinoma. One reason may be a lack of awareness of certain smear patterns of adenocarcinoma in situ (AIS) such as those with crowded small cells (endometrioid pattern). METHODS: A test set of 29 smears (17 AIS with an endometrioid pattern, 12 benign mimics) was reviewed by 11 cytologists (4 experienced cytotechnologists, 3 cytopathology fellows, and 4 cytopathologists with varying levels of experience). Participants were blinded as to the actual diagnosis and the number of cases in each category and were instructed to diagnose either AIS or a benign lesion. Results of this review were not disclosed before a second review conducted after instruction in specific criteria for "endometrioid" AIS. Results were compiled using kappa statistics. RESULTS: In the first round, the ability to distinguish these lesions was poor for 8 of the 11 reviewers, and no reviewer was in excellent agreement with the actual diagnosis. In the second round, only 1 reviewer had a poor rating, and 4 of 11 were in the excellent category. Misdiagnoses in both rounds were more commonly the result of underdiagnosis of AIS than overdiagnosis of benign cases. CONCLUSIONS: The presentation of AIS in smears as groups of crowded small cells is prone to underdiagnosis. Awareness of this problem and use of criteria improves sensitivity. [See editorial on pages 243-4, this issue.] Cancer (Cancer Cytopathol)