Melanotic oncocytic metaplasia of the nasopharynx: a report of seven cases and review of the literature

We describe seven cases of melanotic oncocytic metaplasia of the nasopharynx and review five other cases in the literature. It is usually a small, brown to black lesion that occurs around the Eustachian tube opening, where abundant seromucinous glands and lymphoid tissue are present. Multiple or bilateral lesions are sometimes seen. All 12 reported cases are of Asian origin. Melanotic oncocytic metaplasia occurs predominantly in men (male:female=11:1), with a mean age of 68 years. Simple excisional biopsy appears to be curative. Microscopically, melanotic oncocytic metaplasia is a combination of oncocytic metaplasia of the epithelium of the gland and melanin pigmentation in its cytoplasm. Fontana-Masson staining and immunohistochemical staining of S-100 protein revealed numerous melanocytes with conspicuous dendrites in the glands and stroma, which probably transfer melanin to adjacent glands. The exact pathogenesis of melanotic oncocytic metaplasia is unknown, but we postulate that the lesion could be related to the oncocytic metaplasia of the seromucinous glands around the Eustachian tube, which is followed by the local production and/or acquisition of the melanin pigment, under the influence of certain neuropeptides in the vicinity. The recognition of melanotic oncocytic metaplasia is of clinical importance, as it may be misdiagnosed as a malignancy to the unwary.