Sterile panniculitis in dogs: new diagnostic findings and alternative treatments

The objective of this study was to analyse the underlying diseases, diagnostic findings and treatment outcomes in 10 dogs with sterile panniculitis. There was no significant breed association in this study (P = 0.86).The median age of the dogs was 7.4 years. Concurrent diseases included atopic dermatitis (four dogs), acute pancreatitis (two dogs) and primary hypoadrenocorticism (one dog), with no concurrent conditions detected in three dogs. There was no significant association with the sterile panniculitis (P = 0.57). Well-circumscribed firm nodules were noted in seven dogs, and ill-defined soft nodules were observed in three dogs. Bacterial and fungal cultures of biopsy samples were negative in all cases. Fine-needle aspiration cytology of the nodules revealed pleomorphic mesenchymal cells in all of the well-circumscribed firm nodules, whereas numerous inflammatory cells and adipose cells were evident in soft nodules. These results indicate that firm nodules in panniculitis could be misdiagnosed as tumours. Immunosuppressive therapy was used in eight cases. Topical dexamethasone was used in four dogs, intralesional dexamethasone in one dog, oral prednisolone plus ciclosporin in two dogs and oral prednisolone only in one dog. The remaining treatments were surgical excision and systemic cefalexin in one dog each. The lesions regressed within 1 week in all cases, with more rapid remission following systemic immunosuppressive therapy. This study suggests that cytology may be misinterpreted as neoplastic, especially with firm lesions. In addition, topical glucocorticoid therapy should be further evaluated as a potential treatment for canine sterile panniculitis.