Case report: Long-term local control of recurrent lymphatic malformations using minocycline sclerotherapy following surgical resection in a dog.

Lymphatic malformation is a benign congenital vascular anomaly that is rarely reported in veterinary medicine. Complete surgical excision is extremely challenging because the boundary between the abnormal and normal tissues is poorly defined, which frequently results in recurrence. A 3-year-6-month-old castrated male mixed-breed dog (Chihuahua × Miniature Dachshund) presented with recurrent lymphatic malformations in the left inguinal and peripenile regions. The lesion had previously been surgically excised at another hospital but recurred shortly after surgery. Despite long-term prednisolone therapy, the lesion gradually enlarged, resulting in gait disturbance and decreased activity. Extensive surgical excision was performed at our hospital; however, early postoperative recurrence was observed. Repeat sclerotherapy with minocycline was subsequently administered for the recurrent cystic lesions. The large cystic lesions resolved or remained controlled after treatment, and long-term suppression of lesion progression was achieved. Although small residual lesions persisted, the dog maintained good activity and gait without marked progression at 535 days postoperatively. In addition, amplicon-based targeted deep sequencing of the PIK3CA hotspot regions did not identify any pathogenic variants. This case suggests that repeated minocycline sclerotherapy may represent a potential minimally invasive treatment option for canine lymphatic malformations that are difficult to control with surgical excision alone.