Placental site nodules and plaques. A clinicopathologic analysis of 20 cases.

The clinical and pathological features of 20 cases of a nodular or plaquelike trophoblastic lesion at the placental site, which we have designated "placental site nodule or plaque" (PSN-P), are described. The lesions occurred in patients 27 to 45 years of age, and were discovered in an endometrial curettage specimen performed because of menorrhagia or irregular uterine bleeding, or were incidental findings in curettage or hysterectomy specimens. They were grossly visible in five cases. Microscopic examination disclosed single or multiple, mostly well-circumscribed, oval, or plaquelike, variably cellular nodules that were characteristically extensively hyalinized. The lesional cells typically had abundant cytoplasm that was amphophilic, eosinophilic, or occasionally vacuolated, and irregular, often degenerative-appearing nuclei; mitotic figures were absent or rare. Immunohistochemical staining for human placental lactogen was focally positive in all but one specimen stained; most of the lesional cells stained for cytokeratin. An uneventful follow-up of 1 to 7 years was obtained in 14 cases, including five in which the only treatment was dilatation and curettage. The major lesion to be differentiated from the PSN-P is the placental site trophoblastic tumor. Features favoring the former diagnosis include its usually small size, circumscription, extensive hyalinization, degenerative appearance, and mitotic inactivity. These features, as well as the absence of squamous cells, help distinguish PSN-P from the rare hyalinizing squamous cell carcinoma of the cervix. The available evidence indicates that PSN-P is benign.