Placental site nodule: a clinicopathologic study of 38 cases

This report describes the clinical, histological, and immunohistochemical features of 38 cases of placental site nodule (PSN), a recently described lesion of intermediate trophoblast (IT). The patients ranged in age from 20 to 47 years (mean, 31.1 years). PSNs were diagnosed in endometrial (30 cases), endocervical (seven cases), and both endometrial and endocervical specimens (one case). The majority of biopsies were prompted by an abnormal Pap smear (13 cases) or complaints of menorrhagia (21 cases). All PSNs were microscopically detected, lobulated nodules composed of acellular, hyalinized material admixed with IT. Mitotic activity was noted in seven cases. Immunohistochemically, the IT expressed human placental lactogen (hPL) in 78% of cases and human chorionic gonadotropin (hCG) in 42% of cases, but their expression was weak and focal in contrast to uniform, strong staining for placental alkaline phosphatase (PLAP) (100%), cytokeratins (96%), and epithelial membrane antigen (EMA) (84%). Type IV collagen outlined the IT and stained the extracellular material in the cellular areas. Vimentin-positive cells within the lesions were fewer in number and in a different distribution than those expressing PLAP, CK, and EMA. Two consecutive PSNs occurred in one patient, but no patient developed gestational trophoblastic disease or a significant gynecologic neoplasm.