Progesterone receptor expression in neurofibromas

Neurofibromas are benign tumors of the peripheral nerve sheath, which occur sporadically and in association with the common familial cancer syndrome, neurofibromatosis type 1. There are intriguing links between the growth of neurofibromas and levels of circulating hormones: neurofibromas often first appear around the time of puberty, increase in number and size during pregnancy, and shrink after giving birth. We examined 59 human neurofibromas for the expression of estrogen and progesterone receptors (PRs), because their ligands, estrogen and progesterone, were attractive candidate hormones. The majority (75%) of neurofibromas expressed PR, whereas only a minority (5%) of neurofibromas expressed estrogen receptor. Within neurofibromas, PR was expressed by non-neoplastic tumor-associated cells and not by neoplastic Schwann cells. We hypothesize that progesterone may play an important role in neurofibroma growth and suggest that antiprogestins may be useful in the treatment of this tumor.