14. Manaka L, Kadono S, Kawashima M, Kobayashi T, Imokawa G. The mechanism of hyperpigmentation in seborrhoeic keratosis involves the high expression of endothelin-converting enzyme-1alpha and TNF-alpha, which stimulate secretion of endothelin 1. Br J Dermatol. 2001;145(6):895-903. doi: 10.1046/j.1365-2133.2001.04521.x. PubMed PMID: 11899142.