Radiographic characteristics of canine subungual keratoacanthoma

Subungual keratoacanthoma (SKA) is a rare benign nail bed tumor in dogs, and its radiographic characteristics have not been reported based on the authors' review of the literature. The purpose of this multicenter, retrospective, observational, descriptive study was to describe the radiographic features of SKA in dogs. Twelve dogs for a total of 12 digits with histologically confirmed SKA met the inclusion criteria. The radiographs of the manus or pes were reviewed by two veterinary radiologists and one veterinarian. The radiology reports were interpreted based on a consensus. In six dogs, there was lysis of both the middle phalanx (P2) and the distal phalanx (P3), whereas in the other six dogs, there was only lysis of P3. In all dogs with osteolysis of P2, the lysis involved the distal articular surface. Osteolysis of P3 was more severe in the ungual process than in the ungual crest in all dogs. The margins of the lytic regions of P2 and P3 were well defined and smoothly marginated in most dogs. Expansile changes in the P3 crest were observed in 83.3% (10/12 dogs), and the nail of the affected digit was enlarged and deformed in 91.6% (11/12 dogs). In summary, the radiographic features of canine SKA include severe pressure resorption of the P3 ungual process, expansile change of the P3 ungual crest, and nail enlargement and deformation. With these radiographic features, SKA should be considered as a differential diagnosis.