PLACENTAL SITE TROPHOBLASTIC TUMOR - HUMAN PLACENTAL-LACTOGEN AND PREGNANCY-ASSOCIATED MAJOR BASIC-PROTEIN AS IMMUNOHISTOLOGIC MARKERS

Placental site trophoblastic tumor (PSTT) consists of a neoplastic pro liferation of intermediate or extravillous trophoblast (also known as X cells). Pregnancy-associated major basic protein (pMBP) is a marker for placental intermediate trophoblast. We compared the distribution o f pMBP and human placental lactogen (hPL) in 24 PSTT and 3 exaggerated placental site (EPS) specimens using two distinct immunohistologic me thods, Statistical analyses were wed to compare staining intensities i n metastatic and nonmetastatic lesions. By immunofluorescence, 77% of the PSTT specimens and 100% of the EPS specimens stained with antibodi es to pMBP, and the pMBP was localized in intermediate trophoblast and surrounding extracellular areas. By immunohistochemistry 78% of the P STT specimens and 100% of the EPS specimens stained for pMBP with a pa ttern comparable with that of immunofluorescence, Likewise, by immunoh istochemistry, hPL stained 96% of the PSTT specimens and 100% of the E PS specimens. Immunohistochemical staining intensities for pMBP and hP L correlated (r(2) = +.24; P = .013), but hPL staining was mainly conf ined to intermediate trophoblast and was more intense, Anti-pMBP tende d to stain metastatic PSTT weakly Thus, pMBP is a useful marker for in termediate trophoblast tumors and could help distinguish these from ot her forms of trophoblastic disease. Copyright (C) 1998 by W.B. Saunder s Company.