Cytologic features of undifferentiated and dedifferentiated carcinomas of the endometrium

Background Undifferentiated carcinoma (UC) is a rare, aggressive subtype of endometrial carcinoma. Dedifferentiated carcinomas (DCs) are UCs associated with a component of well differentiated endometrioid carcinoma. The authors sought to describe the morphologic features of UCs and DCs in cytologic specimens. Methods Cytologic specimens from 23 women (aged 46‐86 years; median age, 59 years) were reviewed, including cervicovaginal specimens (n = 7), peritoneal washings (n = 5), touch preparations of core biopsies from various sites (n = 5), fine‐needle biopsies of lymph nodes (n = 3), ascitic fluid (n = 1), pleural fluid (n = 1), and intrauterine fluid (n = 1). Results There were 10 UCs (43%) and 13 DCs (57%). Tumor cells were arranged as single cells (9 UCs, 90%; 12 DCs, 92%) and 3‐dimensional groups (8 UCs, 80%; 11 DCs, 85%). Most cases showed high nuclear‐to‐cytoplasmic ratios. Nuclear molding was observed in 3 UCs (30%) and in 5 DCs (38%). Nuclear chromatin was often coarsely granular 6 UCs, 60%; 9 DCs, 69%). Nucleoli were inconspicuous in some cases (6 UCs, 60%; 8 DCs, 62%) but were appreciable in others. Necrosis was observed in 5 UCs (50%) and in 5 DCs (38%). Most cases exhibited clean backgrounds, and a few showed acute inflammation. Comparison of the cytologic features of UCs and DCs did not reveal any statistically significant differences. Conclusions UCs and DCs have a spectrum of cytomorphologic appearances that are not pathognomonic, but the presence of some of these (relatively uniform population of predominantly singly dispersed cells with high nuclear‐to‐cytoplasmic ratios and variably conspicuous nucleoli) should prompt consideration of UC and DC in the differential diagnosis.