Background: Merkel cells are neuro-endocrine cells present in the basal layer of the human epidermis and the outer root sheath of hair follicles. Objective and Method: In order to gain further insight into the as yet ill-defined involvement of Merkel cells in skin diseases, we studied the distribution of these cells in formalin-fixed, paraffin-embedded sections of 165 inflammatory, hyperplastic or tumoral skin lesions of various anatomic locations, with a monoclonal antibody to keratin 20. Results: Lesions with frequently increased Merkel Cell numbers included actinic keratosis, fibrous papules of the face and some conditions with (immature) hair follicle differentiation. Conclusion: These results suggest that Merkel cell hyperplasia is unrelated to epidermal proliferation but that it is rather specific to a limited number of skin diseases.

Keywords:
Merkel cells, Epidermal hyperplasia, Cutaneous tumours, Keratin 20
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