Proliferations and tumors of intermediate trophoblast of the placental site.

The clinical and pathologic features of proliferations and tumors of intermediate trophoblast of the placental site are reviewed. These lesions include the exaggerated placental site reaction, which is a florid form of the process that occurs normally at the placental site; a hitherto undescribed variant of this lesion, which we have designated placental site nodule, and the neoplasm of intermediate trophoblast that has been termed placental site trophoblastic tumor. Problems encountered in distinguishing these lesions from one another and from nontrophoblastic lesions, particularly in endometrial biopsy specimens and curettings, are discussed.