Clinical, histological and prognostic features of a novel nail-bed lesion of cats: 41 cases

Objectives There is a distinct subset of lesions arising on the digits of cats, located at or close to the nail-bed epithelium, which are typically composed of proliferative fibroblast-like cells, multinucleate giant cells and areas of osseous metaplasia, but currently there is no published literature detailing the clinical or histological features of these lesions. Methods This study identified 41 such cases from two large commercial diagnostic laboratories and assessed various histological and clinical features; 22 cases had additional follow-up data available. Results All masses in this study were exophytic, variably inflamed, contained large numbers of spindle cells and had areas of capillary formation. The majority also had areas of ulceration, multinucleate giant cells and osseous metaplasia. The mitotic count was variable, but mitoses were confined to the fibroblast-like cells. Male cats appeared predisposed and the second digit was the most commonly affected. Conclusions and relevance These distinctive lesions arising on the digits of cats had potential for local recurrence but metastasis was not reported. Based on these clinical and histological features, the masses in this study appear most similar to giant cell reparative granulomas, and trauma, injury to the nail or nail-bed and nail-bed infections may potentially contribute to their development.