Well-differentiated inflammatory liposarcoma with metastasis in a 6-y-old cat.

Liposarcomas are rare malignant tumors showing adipocytic differentiation. We report a well-differentiated liposarcoma in a 6-y-old, male neutered cat with a prominent inflammatory component and metastatic spread to the lungs. The patient was initially presented because of fever, lethargy, and a firm subcutaneous inguinal mass. A Tru-cut biopsy of the mass revealed a mixture of well-differentiated adipocytes and lymphoplasmacytic-histiocytic inflammation, interpreted as panniculitis. The mass was surgically excised but recurred 4 mo later. A second excisional biopsy yielded similar histologic findings. A third recurrence of the mass was associated with lung nodules. Histopathology of the recurring and metastatic masses confirmed the diagnosis of well-differentiated inflammatory liposarcoma with pulmonary metastases. The neoplasm had an intense inflammatory component, which obscured the underlying features of liposarcoma and made differentiation from steatitis difficult. This inflammatory variant of a well-differentiated liposarcoma should be considered as a differential in tumorous steatitis-like lesions.