| These pleomorphic, mesenchymal tumors composed of fibroblasts and histiocytic cells (often present as multinucleated giant cells) remain poorly defined in veterinary medicine. A lesion called
canine fibrous histiocytoma
(nodular granulomatous episclerokeratitis, nodular fasciitis,
proliferative keratoconjunctivitis, conjunctival granuloma, Collie granuloma) is recognized at the episcleral junction and cornea primarily in young to middle-aged (2-4 yr old) Collies, but the histologic features are more suggestive of a granulomatous inflammatory response than a neoplasm. As might be
expected for a noninfectious inflammatory process, these are generally responsive to sublesional injections of 10-40 mg of methylprednisolone. |
|
Malignant fibrous histiocytomas
(extraskeletal giant cell tumors,
giant cell tumors of soft parts, dermatofibrosarcomas) are most frequently found in the skin and soft tissues of cats, occasionally found in horses and mules, and rarely in the skin of other domestic species, including dogs. In cats, malignant fibrous histiocytomas are most common on the distal extremities or ventral cervical regions of the aged but may also be
diagnosed at vaccination sites. In horses and mules, these have been described as giant cell tumors of soft parts. Occurring in young adult to middle-aged Equidae, they are firm, nodular to diffuse swellings that are white on cut surface, with variable hemorrhage. Malignant fibrous histiocytomas are sarcomas of intermediate malignancy. They are locally invasive and tend to recur after attempts at complete excision but seldom metastasize. Radical excision is recommended. |
