Introduction: Melanocytes in skin are derived
from the neural crest and colonize the epidermis in the
first trimester of gestation. Melanocytes have been
observed in the nasopharyngeal, inner ear and oral
mucosa and should therefore be present in the middle ear
mucosa. Aims: To identify and determine the
distribution of melanocytes in human cholesteatoma and
normal meatal skin in Caucasian adults. Material and
methods: Human cholesteatoma (n=18) and normal
meatal skin samples (n=10) were investigated
immunohistochemically with anti-HMB-45 and MART-
1 antibodies. Localization and distribution of
melanocytes were assessed in the epidermis and
cholesteatoma using an automatic analyzing system.
Results: Regular skin exhibited melanocytes within the
epidermis and accounted for 10% of the total cell
number. They occurred partly as membrane-bound
clusters. Cholesteatoma matrix melanocytes were
observed in the basal layer and exhibited an oval or
roundmorphology. Decreased numbers of melanocytes in
the basal layer correlated with keratinization within
cholesteatoma samples. Melanocytes revealed
monomorphous nuclei, abundant cytoplasm containing
particles of melanin. Found adjacent to glands and blood vessels, melanocytes were also scattered among the
mesenchymal cells. Accounting for 2-6% of the total cell
number within the squamous epithelium, melanocyte
density was significantly lower in cholesteatoma tissue
than in skin. Conclusions: The melanocyte distribution
pattern was different when comparing the epithelia of
skin and cholesteatoma. The presence of melanocytes in cholesteatoma may be due to an ingrowth, consequently
controlled by keratinocyte-derived signals. In terms of
the pathogenesis of cholesteatoma, neither squamous
metaplasia nor melanocyte metaplasia can be excluded
by our data