Leiomyosarcoma of soft tissue in a cow.

A 4-year-old Holstein cow developed a large neoplastic mass, which was formed in the deep soft tissue of the neck and removed surgically. The neoplasm was shown to be a smooth muscle tumour by the presence of alpha smooth muscle actin and fine intracytoplasmic filaments with focal densities. This malignant neoplasm showed extensive areas of necrosis and haemorrhage, high cellularity, marked pleomorphism, atypical giant cells and numerous mitoses with occasional abnormal figures.