Effects of hormone replacement therapy on fine needle aspiration cytology of the breast

To investigate the possibility that hormone replacement therapy (HRT) might induce morphologic changes in breast cytology simulating malignancy, we determined the subjective interpretation and objective morphometric features of 39 fine needle aspiration cytology samples from women who were using a variety of HRT preparations. Cases were matched for age and final diagnosis (assessed by a triple approach) with women who had never used HRT. Cytocentrifuge preparations stained with Papanicolaou stain were assessed by two observers for cellularity and diagnosis. Although diagnostic accuracy was slightly higher in HRT than non-HRT samples, there was no significant difference in the assessments of cellularity and diagnosis between the two observers or between HRT and non-HRT samples. Nuclear areas in HRT samples were larger than in non-HRT samples, measured using computerized image morphometry; this difference did not induce the observer to diagnose malignancy more frequently. HRT had no adverse effect upon the accuracy of interpreting breast fine needle aspiration cytology samples.