Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma) of the Head in a Dog

A six year-old intact female miniature poodle was presented with a soft mass of the forehead region. Computed tomography identified generalized frontal bone loss and a large extracranial mass, which had a low attenuation area of hemorrhagic necrosis with septation and enhancement of solid components. In magnetic resonance imaging, the mass was isointense in T1-weighted images except its fluid parts and hyperintense in T2-weighted images with lobulated by low-signal septa. Surgery was performed to remove the mass, and histopathologic examination revealed that the mass was consistent with undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). The dog died from the rapidly recurrent mass and severe pulmonary metastasis.