Atypical Placental Site Nodule Arising in a Postcesarean Section Scar: Case Report and Review of the Literature.

The distinction between benign and malignant trophoblastic lesions often presents a diagnostic challenge, even in entities with defined morphologic and immunohistochemical criteria. Lesions arising from chorionic-type intermediate trophoblast, namely placental site nodule (PSN) and epithelioid trophoblastic tumor (ETT), can be distinguished by existing criteria. However, a putative intermediate lesion termed "atypical placental site nodule" (APSN) has been described in the literature but is not well-classified. We present a case of APSN, along with a brief literature review, and we propose more definitive morphologic and immunohistochemical criteria for this entity, in order to facilitate easier diagnosis and gather more information regarding outcomes.