Mucinous nevus (MN) is an entity recently described1 and classified in the spectrum of einevi.2 We report a new case of MN with adult onset and present its nosography.
Report of a Case.
A 27-year-old man presented with a 5-year, 15-cm-long, mamillated, slightly keratotic, graybrown plaque of coalescent, linearly arranged papules on the lower back (Figure 1). Results of laboratory tests, including thyroid function tests and protein electrophoresis, were normal. Histopathologic findings revealed an acanthotic epidermis with thin, elongated rete ridges and orthohyperkeratosis. In the papillary dermis, fine collagen fibers were interspersed in an abundant ground substance (Figure 2) that stained positively with Alcian blue at pH 2.5 while it was negative at pH 0.5. A periodic acid— Schiff reaction was negative. Fibroblasts were increased without any inflammatory infiltrate. A Congo red stain for amyloid was negative. With the van Gieson and elastic tissue stains, the mucinous