A clinicopathologic analysis of 15 patients with glassy cell carcinoma confirmed that this is a rare disease, having an incidence of 1.2%. It is a rapidly progressive and biologically aggressive disease with early extrapelvic metastasis. The five-year survival and the median survival in our series were 28% and 14 months, respectively. The majority of patients (87%) were understaged, which may have played a role in the poor prognosis. Four of 12 patients (33%) were initially diagnosed as having a benign disease (false-negatives). Defining of cytologic characteristics and differential features of this tumor may facilitate an early and more accurate diagnosis to improve prognosis.