Increased number of MCs correlates with upregulated number of TrkA⁺, TrkB⁺, and TrkC⁺cells infiltrating the dermis in CM. Toluidine blue (A-C), anti-TrkA (D-F), anti-TrkB (G-I), and anti-TrkC (J-L) staining of skin biopsies of healthy control participants (CTR) and patients with mastocytosis (MAST; lesional skin). Immunohistochemistry stainings of a representative paraffin section of healthy skin (A, D, G, J), CM (B, E, H, K), and mean values and SEMs of the number of cells in the upper (left side) and lower (right side) dermis of 10 control participants and 10 patients with mastocytosis (C, F, I, L: n = 5 for CM; n = 4 for ISM; and n = 1 for SM-AHNMD) are depicted.