OBJECTIVETo investigate the clinicopathological features of intermediate trophoblastic non-tumor lesions, and to evaluate the position of immunohistochemistry in differential diagnoses.

METHODSClinical presentation and morphological study of 15 cases of exaggerated placental site (EPS) and 4 cases of placental site nodule or plaque (PSNP) were reviewed. Immunohistochemical stains for hCG, hPL, inhibin-alpha, PLAP, CK18 and Ki-67 were performed.

RESULTSThe age of patients ranged from 25 to 40 years with an average of 31.5 years for EPS and 26 to 39 years with an average of 34.3 years for PSNP. Microscopically, EPS was characterized by cords and small sheets of implantation site intermediate trophoblasts infiltrating the endometrium, myometrium and arterial walls. The general histological structures of the endometrium and myometrium were preserved. PSNP was characterized by multiple circumscribed nodular lesions consisting of so-called chorionic-type intermediate trophoblasts and hyaline-like matrix present in the endometrium. Immunohistochemical stainings for hPL and CK18 were positive in the 15 EPS cases. Immunoreactivity for CK18, Inhibin-alpha and PLAP was detected in 4 PSNP cases. The Ki-67 labeling index in 15 EPS cases was low (< or = 5%), while Ki-67 index in 4 PSNP cases was close to 0.

CONCLUSIONSThe clinical presentation and pathological features of EPS and PSNP differ from those of trophoblastic tumors (placental site trophoblastic tumor, epithelioid trophoblastic tumor and choriocarcinoma). Immunochemical staining is of great value in their differential diagnoses.