Diagnostic and Clinical Insights into an Infiltrative Lipoma in a Dog

Infiltrative lipomas are rare benign neoplasms originating from adipocytes that differ from conventional lipomas by their locally invasive behavior, often infiltrating adjacent tissues such as muscles, tendons, and joint capsules. This report describes a case of an infiltrative lipoma in a 9-year-old, 33 kg, intact female Boxer dog presenting with a progressive perineal mass over two months. Physical examination revealed a firm swelling in the perianal region, and laboratory tests indicated elevated ALT and alkaline phosphatase levels. Abdominal ultrasonography showed no hepatic alterations but suggested ovarian cysts as a differential diagnosis. Surgical excision was performed, revealing that the mass infiltrated the semitendinosus and semimembranosus muscles, partially encasing the urethra and large intestine. Histopathological analysis confirmed a well-differentiated adipocyte proliferation infiltrating muscle bundles without cellular atypia, consistent with an infiltrative lipoma. The patient recovered uneventfully postoperatively, although follow-up information was unavailable due to loss of contact with the owner. This case highlights the importance of thorough diagnostic evaluation and surgical planning in managing infiltrative lipomas, which, despite their benign nature, can present significant surgical challenges due to their invasive growth. Further studies are needed to determine their prevalence and behavior in small animal clinical practice.