[Cutaneous heterotopic meningeal nodules].

Cutaneous heterotopic meningeal nodules are rare lesions whose pathogenesis remain discussed. They are typically located on the scalp or the rachidian axis. They often are congenital and diagnosed during childhood or young adulthood. There are two admitted theories for pathogenesis of heterotopic meningeal nodules: (1) tumoral proliferation of ectopic arachnoïdal cells (true cutaneous meningioma), (2) meningocele-type developmental defect (rudimentary meningocele). Histological and immunohistochemical aspects are characteristic, showing arachnoidal cells, EMA+ and vimentine+, that infiltrate collagene and whorl around collagene or psammomatous bodies. We report the expression of progesterone receptor (PR) in a cutaneous heterotopic meningeal nodule on the scalp of a 23-year-old man, and propose this PR expression as a new diagnosis tool for such lesions.