A case of granular cell ameloblastoma (GCA) was studied by light microscopy and histochemistry. Microscopically, the lesion showed small groups or large clusters of granular neoplastic cells, with pyknotic and hyperchromatic nuclei, oriented away from the basement membrane, in a back-to-back arrangement. The "granular change" is thought to be due to a dysfunctional status of neoplastic cells, and the pathogenesis of this tumour seems to be age-related. The prognosis of GCA is good, generally corresponding to that of the classical ameloblastoma; as yet, only one case has been described with a more aggressive biological behaviour (high recurrence rate).