PMEL and pheochromocytoma: In one case series, it was found that in one-third of the cases of pheochromocytoma, there were HMB45-positive cells, which comes as no surprise because the cells of the adrenal medulla or pheochromocytes are derived from the neural crest in the same way as melanocytes, and HMB45 antibody stains tumors derived from the neural crest.