Fig. 3: Melanosomes diffuse outward from primary and metastatic tissues.

a Immunohistochemical (IHC) analysis of an in situ melanoma showing mature melanosomes stained with anti-GPNMB (green) diffusing rightward into the underlying subcutaneous tissues and away from the primary melanoma tumor. HMB45 (red), an antibody for PMEL, which stains the premelanosome, shows the location of the melanoma. Nuclei were stained blue with DAPI. Equally sized, equidistant zones were delineated on the image in order to quantify differences in the intensity of GPNMB displayed by the graph to the right of the image. b IHC investigation of the metastatic sites: lymph node (top), liver (middle), and brain (bottom) showing secretion and dispersion of mature melanosomes stained with GPNMB (green) into the stroma (S) surrounding the tumor (T), stained with HMB45 (red). Nuclei were stained blue with DAPI.