Morphology and distribution of eosinophilic granulocytes in damselfish neurofibromatosis, a model of mast cell distribution in neurofibromatosis type 1

Mast cells (MC) are a conspicuous component of neurofibromas in humans. The present study is based on damselfish neurofibromatosis (DNF) a naturally occuring animal model of neurofibromatosis type 1. Investigations of leukocytes of fishes have generally concluded that these animals lack metachromatic, basophilic mast cells and that the apparent analog in fishes is an eosinophilic granule containing cell (EGC). EGC were found at high densities in both naturally occuring neurofibromas in DNF and in those produced in laboratory transmission experiments. Tumors induced by injection of cells from cultured DNF tumor cell lines exhibited significantly higher densities of EGC than did spontaneously occuring tumors or those induced by injection of homogenized tumor tissue. EGC were significantly more common in the outer 200 μm edge of the tumors. We believe that these EGC are the piscine equivalent of the mammalian MC and that their presence in tumors in DNF will provide the first opportunity to experimentally manipulate this type of cell in neurofibromas.