Placental site nodule (PSN) as a pitfall in histological diagnosis of the uterus

Aims: A placental site nodule (PSN) is the remnants of intermediate trophoblast, residual from a previous pregnancy that is usually an occasional finding in patients operated for other causes. In some situations the nodule can interfere with the histopathological diagnosis inasmuch as it creates difficulty in the differential diagnosis, not only with analogue trophoblast lesions [placental site trophoblastic tumour (PSTT) and epithelioid trophoblastic tumour (ETT)] of greater seriousness but also with the functional or organic pathology which was the original reason for the surgical intervention. Materials and Methods: Herein the authors present four cases of PSN with particular characteristics localised in the cervix (two cases) and in the endometrium (two cases). Results: In the first case an abnormal Pap test result (LSIL) led to a biopsy with the mistaken diagnosis of infiltrating squamous carcinoma, subsequently corrected by cervical conization biopsy. Follow-up revealed a miscarriage and a successful full-term pregnancy four years after the surgical operation.Two other cases were found in patients with concomitant malignant neoplasia (respectively breast and ovary) while the last case was in concomitance with uterine leiomyoma. Conclusions: The diagnoses were convalidated with suitable immunohistochemical analysis (cytokeratin, PLAP, hPL, P63, and β-hCG).

PSN, pitfall, histopathology.

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