Breed predilections and prognosis for subungual squamous cell carcinoma in dogs

Objective To better document the prevalence, breed predilections, and clinical behavior of subungual squamous cell carcinomas in dogs. Procedure Retrospective analysis of records from 278 812 canine biopsy submissions including 1518 subungual squamous cell carcinomas from dogs in Canada between the years 2003 and 2021. Results In agreement with previous studies, giant schnauzers [odds ratio (OR): 56.7], standard schnauzers (OR: 20.3), Gordon setters (OR: 18.3), black standard poodles ( OR: 11.1), Kerry blue terriers ( OR: 9.4), Rottweilers (OR: 7.0), and several other breeds of large black dogs had a strong predilection for development of subungual squamous cell carcinomas. In giant schnauzers and standard poodles specifically, the risk of developing additional tumors on additional digits was 56%. There were no local postoperative recurrences, and the risk of detecting metastatic disease within 5 y after initial diagnosis was very low at 4%. Conclusion Moderately large black, or black and tan, dogs have a marked increase in the prevalence of subungual squamous cell carcinomas. At least in giant schnauzers and black standard poodles, the risk of developing additional similar tumors on additional digits is high, but the metastatic risk is very low. Clinical relevance Veterinarians receiving a histologic diagnosis of subungual squamous cell carcinoma in a large black (or predominantly black) dog should advise the owners of a substantial risk that the dog will develop similar tumors on other digits in 2 or 3 y following initial diagnosis, but that the risk of local recurrence or metastatic spread is extremely low.