Final Diagnosis: Pigmented Onychocytic Matricoma
Diagnosis comment: The biopsy is most consistent with an onychocytic matricoma based on the hyperplastic bulbous quality of the rete pegs of matrical origin defining the essence of an onychocytic matricoma. It is reasonable to use the adjectival modifier of pigmented to denote the proliferation of lightly pigmented Fontana-Masson, tyrosinase positive dendritic melanocytes within the matrical epithelium.