Combined with previously published molecular signatures, which demonstrate that MCN tumors show significantly increased expression of key steroidogenic enzymes such as aromatase (CYP19A1), 17α-hydroxylase/17,20 lyase/17,20 desmolase (CYP17A1), 17β-hydroxysteroid dehydrogenase 1 (HSD17B1), steroidogenic acute regulatory protein (Star), and cholesterol side chain cleavage enzyme or cholesterol desmolase (CYP11A1) (Van Treeck et al., 2020), this provides convincing evidence that the stroma of MCNs produces estrogen locally, similar to what is observed in the normal ovary. The gene discussed is CYP11A1; the disease is lipoid nephrosis.