Finasteride has been associated with the development of gynecomastia. Altho
ugh cytoplasmic vacuolization has been noted in prostatic epithelium in men
taking this drug, we found no documentation of the cytologic changes in fi
nasteride-associated gynecomastia. We present the case of a 53-year-old man
who developed unilateral gynecomastia following finasteride therapy for al
opecia. A fine-needle aspiration biopsy of the mass was diagnosed as adenoc
arcinoma on the basis of nuclear atypia and particularly because of cytopla
smic vacuolization. Subsequent excisional biopsy revealed benign gynecomast
ia with no evidence of malignant change. The ductal epithelium did exhibit
cytoplasmic vacuolization similar to that described in the prostate followi
ng finasteride therapy. We believe this is the first reported case document
ing the cytologic changes seen in gynecomastia secondary to finasteride the
rapy. Cytoplasmic vacuolization in this setting should not be considered ev
idence of malignancy in men with gynecomastia. As with gynecomastia in gene
ral, extreme caution should be used before rendering a cytologic diagnosis
of malignancy.