The American Journal of dermatopathology
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This second part of the review categorizes the site-specific nail tumors, as proposed in the first part, according to their clinical presentations. Acquired localized longitudinal pachyonychia allows for the specific recognition of onychogenic nail tumor, which can be classified into 2 groups according to the predominant compartment of origin within the nail unit as follows: epithelial tumors encompassing onychocytic matricoma and onychocytic carcinoma, and fibroepithelial tumors: the so-called onychomatricoma. As onychomatricoma is neither an epithelial matrical tumor nor a tumor with a limited differentiation toward the matrix, the author proposes instead the descriptive term of panonychoma fibropapilliferum (POP). ⋯ The author proposes to categorize subungual tumors into 2 types: subungual skin tumors (including subungual skin metastasis from internal malignancies) and nail tumors. Nail tumors can be accurately classified using a combined clinical and histogenetic approach. This new and expanding group of appendageal tumors is important for both dermatologists and dermatopathologists for the potential early detection of a malignant lesion or for the avoidance of overtreatment of a benign lesion.