While P450arom mRNA is not detectable in the eutopic endometrium of disease-free women, it is detected in the endometriotic tissues as well as eutopic endometrium of EM patients (Noble et al., 1996), and E2 is a potent stimulator of P450arom expression in cultured stromal cells derived from the eutopic endometrium as well as ovarian endometriomas of women diagnosed for EM (Noble et al., 1997). The gene discussed is CYP19A1; the disease is erythema multiforme.