Intermuscular Xanthoma between the abdominal oblique muscles mimicking soft tissue neoplasia in a dog

CASE REPORT: An 11-year-old neutered male Belgian Malinois, a retired military working dog, presented with gradually enlarging soft tissue masses in the right abdominal wall and left gluteal region. Computed tomography revealed a well-defined intermuscular mass located between the external and internal abdominal oblique muscles. Cytologic findings were suggestive of foamy macrophages, and histopathologic examination confirmed the diagnosis of xanthoma. Mild hypercholesterolemia with otherwise unremarkable lipid and endocrine profiles was observed. CONCLUSION: The lesion’s intermuscular location, combined with the dog’s history of repetitive physical activity during working service, suggests that chronic mechanical strain may have contributed to lesion development. This case represents an atypical presentation of xanthoma mimicking a soft tissue neoplasm in an uncommon anatomic site. A brief review of previously reported canine xanthoma cases is included to highlight anatomic variability and potential predisposing factors. KEY CLINICAL MESSAGE: Xanthoma can occasionally develop in atypical intermuscular locations and may mimic soft tissue neoplasia. In active or working dogs, repetitive mechanical stress combined may represent potential contributing factors, although definitive causation remains uncertain. Clinicians may need to be aware of this possibility to avoid overinterpretation of benign xanthomatous lesions as neoplastic processes.