Skin of Patients with Large/Giant Congenital Melanocytic Nevi Shows Increased Mast Cells.

Nevocytes (NC) and mastocytes (MC) have different progenitors but share stem cell factor as regulator/ activator of NC and for differentiation/proliferation of MC. Both cell types express stem cell factor receptor CD 117. We hypothesize that large/giant congenital melanocytic nevi (L/GCMN) may associate with MC hyperplasia. Forty-nine L/GCMN were examined, 12 samples from uninvolved skin of L/GCMN patients and 6 control skin samples studied with Giemsa and immunohistochemistry for CD117 and MC-tryptase. Picrosirius red (PR) was used to assess fibrosis. Digital images were used to count MC/mm² using ImageJ software. Western blot (WB) for MC-tryptase in 12 GCMN and 12 nonnevus samples was performed. Analysis of variance (Tukey) and Pearson statistical tests were applied. Increased MCs were observed in nevus tissue (75.1 ± 35.3 MCs/mm²) and in uninvolved skin (53.74 ± 27.7 MC/ mm²). P = 0.109 from patients with L/GCMN, compared with controls from individuals without L/ GCMN (28.74 ± 8.4 MC/mm²); P = 0.001 supported by results of WB analysis for tryptase. A positive trend toward correlation of MC numbers with fibrosis, assessed by PR staining fell short of statistical significance (r = 0.245; P = 0.086); no difference in fibrosis was found between nevus and non-nevus skin from patients with L/ GCMN (P = 0.136). We found a higher density of MC, both in normal-appearing skin and nevus areas of L/ GCMN patients, compared with control skin samples from individuals without nevi. Given the abnormal wound healing and allergic reactions described in L/GCMN patients, these findings suggest a potential role for MC in the biology of L/GCMN, making them a potential target for therapeutic intervention. [ABSTRACT FROM AUTHOR]