Placental site nodule (PSN): an uncommon diagnosis with a common presentation.

Placental site nodule (PSN) is a rare benign lesion of the intermediate trophoblast which is thought to represent incomplete involution of the placental implantation site. PSN usually presents as menorrhagia, intermenstrual bleeding or an abnormal Pap smear. PSN is benign, but it is important to distinguish it from the other benign and malignant lesions like decidua, placental polyp, exaggerated placental site and placental site trophoblastic tumour. Follow-ups of typical PSNs do not show recurrence or malignant potential. PSN is an uncommon condition which should be suspected in cases of abnormal bleeding, especially following uterine surgical procedures preceding last pregnancy. Timely diagnosis and treatment is necessary to differentiate it from potentially malignant placental lesions with a similar presentation.