A clinicopathological study of 57 unicystic ameloblastomas has been undertaken, which represents 15% of all cases of ameloblastoma accessioned in our department over a 30‐yr period. Of the cases where gender was recorded: 30 were male and 23 female. The majority of patients were black (51 cases) and most occurred in the mandible (52). This distribution conforms to that of solid and multicystic ameloblastomas. The mean age at diagnosis was 23.8 years (S.D. 14.9) which is significantly younger than for the conventional counterpart (p <0.1%). The lesions were classified histologically into 3 groups: Group 1 (42%) cyst lined by a variable often non‐descript epithelium; Group 2 (9%) cyst showing intraluminal pelxiform proliferation of epithelium; Group 3 (49%) cyst with invasion of epithelium into the cyst wall in either follicular or plexiform patterns. While Group 1 and 2 lesions may be treated by enucleation, Group 3 lesions should be treated aggressively as for conventional ameloblastomas. The objectives of correct histological diagnosis, sub‐classification and appropriate therapy are best achieved by enucleation biopsy. There is little evidence to support origin from pre‐existing odontogenic cysts.

Our results suggest that ghost cell odontogenic tumours comprise a heterogeneous group of neoplasms which need further studies to define more precisely their biological behaviour.

This updated review based on the largest number of AOT cases ever presented, confirms the distinctive, although not pathognomonic clinicopathological profile of the AOT, its worldwide occurrence, and its consistently benign behaviour.

The presence of melanocytes in the oral epithelium is a well-established fact, but their physiological functions are not well defined. Melanin provides protection from environmental stressors such as ultraviolet radiation and reactive oxygen species; and melanocytes function as stress-sensors having the capacity both to react to and to produce a variety of microenvironmental cytokines and growth factors, modulating immune, inflammatory and antibacterial responses. Melanocytes also act as neuroendocrine cells producing local neurotransmitters including acetylcholine, catecholamines and opioids, and hormones of the melanocortin system such as proopiomelanocortin, adrenocorticotropic hormone and α-melanocyte stimulating hormone, that participate in intracellular and in intercellular signalling pathways, thus contributing to tissue homeostasis.There is a wide range of normal variation in melanin pigmentation of the oral mucosa. In general, darker skinned persons more frequently have oral melanin pigmentation than light-skinned persons. Variations in oral physiological pigmentation are genetically determined unless associated with some underlying disease.In this article, we discuss some aspects of the biophysiology of oral melanocytes, of the functions of melanin, and of physiological oral pigmentation.