Transepithelial Elimination in Papular Mucinosis

To the Editor.—  Transepithelial elimination (TE) is a recognized mechanism in the formation of keratotic papules and nodules in a variety of skin diseases. Dermatoses displaying this phenomenon include calcinosis cutis, osteoma perforans, granuloma annulare, elastosis perforans serpiginosa, reactive perforating collagenosis, and perforating folliculitis, as initially reported by Mehregan.¹ This list has been expanded to include Kyrle's disease,^2,3 necrobiosis lipoidica,⁴ pseudoxanthoma elasticum,⁵ chondrodermatitis nodularis chronica helicis,⁶ cutaneous chromomycosis,⁷ eruptive vellus hair cysts,⁸ and malignant melanoma.⁹Transepithelial elimination can be suspected clinically when indolent keratotic papules fail to respond to treatment that is usually successful in diseases displaying a localized epidermal hypertrophy. The histologic pattern of TE is essentially the same within this heterogenous group and consists of the following: (1) epidermal hyperplasia, (2) a central crater with a keratinous plug, (3) direct communication of the crater to histochemically altered material in the