Postcesarean delivery uterine diffuse intermediate trophoblastic lesion resembling placental site plaque

We describe a highly unusual lesion characterized grossly by the formation of a cavity within the lower uterine segment and upper endocervix that communicated with bilateral fistulae to both parametria. Histologically, the cavity and fistulous tracts were entirely coated by fibrinous material with underlying intermediate trophoblastic cells with atypical degenerate nuclei, absent mitotic activity, and a low MIB1 proliferation index. The overall cellular morphology of the lesion was similar to that of the well-circumscribed placental site nodule or plaque. Apart from the lining of the fistulae, there was no invasion of the myometrium by the trophoblastic cells. The patient had undergone previous cesarean deliveries; the lesion was related to the surgical site and was probably secondary to the previous surgery. In a review of the literature, we identified only a single previous report of a somewhat similar case. We propose the term uterine diffuse intermediate trophoblastic lesion resembling placental site plaque for this rare condition.