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Hemangiomas of the skin and soft tissues are benign proliferations that closely resemble blood vessels. Whether these are neoplasms, hamartomas, or vascular malformations remains undefined, and no clear criteria exist that allow for their separation. They are most commonly identified in dogs, occasionally in cats and horses, and rarely in cattle and pigs; they are an exceptional finding in other domestic animals. In dogs, they are tumors of adult dogs and most commonly
develop on the trunk and extremities. Many canine breeds (including Gordon Setters; Boxers; and Airedale, Scottish, and Kerry Blue Terriers) are considered to be at risk. Cats most frequently develop hemangiomas when they are adults. Lesions are most common on the head, extremities, and abdomen. In horses, they are most common on the distal extremities of young (<1 yr old) animals. In cattle, they may be seen as congenital lesions or in older animals. Dairy cattle are predisposed
to developing
disseminated hemangiomas (angiomatosis) in the skin and internal organs. In pigs, these lesions generally develop in the scrotal or perineal skin of Yorkshire, Berkshire, and less commonly Chester White boars. In the first 2 breeds, the disease is believed to be genetically transmitted. Hemangiomas are single to multiple, circumscribed, often compressible, red to black nodules. The
lining epidermis may be unaffected or ulcerated or papillated. Small, superficial hemangiomas that often appear as a “blood blister” are known as angiokeratomas. When erythrocytes are sparse or absent within vascular lumens, the term lymphangioma is applied. Hemangiomas are benign, but their tendency to ulcerate and grow quite large, along with the importance of confirming the diagnosis to make a
prognosis, indicate removal. Excision is the treatment of choice; however, in large animals in which the lesions may be large and involve the distal extremities, this may be difficult. In these cases, cryosurgery or radiation therapy may be necessary. Except in dairy cattle with angiomatosis, development of additional tumors at new sites after complete excision is uncommon. |
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Hemangiopericytomas
(canine spindle-cell sarcoma,
canine malignant fibrous histiocytoma,
canine neurofibrosarcoma,
canine perineuroma) are common in dogs and rare in cats (if they occur at all). This tumor was initially named because it was thought to be derived from fibroblastic cells that surround small vessels; however, the appropriateness of the name remains a topic of debate. These tumors develop most commonly on the distal extremities and thorax of older dogs. Females appear to be predisposed, and Siberian Huskies, mixed-breed dogs,
Irish Setters, and German Shepherds are most at risk. Hemangiopericytomas typically present as firm, multilobulated, solitary lesions with irregular borders, most commonly in the subcutaneous fat but sometimes in the dermis. They are of intermediate malignancy and have limited metastatic potential. Complete excision is the treatment of choice but, due to their infiltrative nature, ~30% recur. If the first excision of any sarcoma is not adequate, followup surgery to completely
remove the tumor bed is indicated. At surgery, intralesional chemotherapy with carboplatin and intraoperative radiation therapy may improve the tumor-free interval. Followup external beam radiation therapy may also be considered as an option to control local recurrence following incomplete excision or narrow margins. |
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Angiosarcomas, arguably the most aggressive of all soft-tissue tumors, are composed of cells that have many functional and morphologic features of normal endothelium. Although these tumors are often divided into hemangiosarcomas (of purported blood vessel origin) and lymphangiosarcomas (of lymphatic vessel origin), such a distinction is arbitrary. The term
angioendothelioma is also used. These tumors generally arise spontaneously, but in dogs with short, often white coats, chronic solar injury has induced a change in the superficial vascular plexus, which initially appears as a hemangioma and then progresses to a malignant vascular tumor. The breeds prone to actinically induced angiosarcomas are Whippets, Italian Greyhounds, White Boxers, and Pit Bulls. Pathologists will often diagnose these lesions as cutaneous hemangiosarcomas. |
| Angiosarcomas of the skin and soft tissues are seen in all domestic animals but are most common in dogs, generally in adult or aged animals. In dogs, they most frequently develop on the trunk, hip, thigh, and distal extremities. In addition to the breeds prone to actinically induced angiosarcomas, Irish Wolfhounds, Vizslas, Golden Retrievers, and German Shepherds are also at risk. In cats, this tumor is seen most commonly in older, neutered males, on the extremities and trunk. Cats
with skin, subcutaneous, or visceral involvement develop distant metastasis. Angiosarcomas can vary markedly in appearance. Most commonly, they appear as one or more erythematous nodules present anywhere in the skin or underlying soft tissues. Less frequently, they appear as a poorly defined bruise. All grow rapidly, often are associated with large zones of necrosis and thrombosis, and typically are red to black on cut section. Tumors often diagnosed as lymphangiosarcomas may have
much less lumenal blood, and the vascular spaces are typically filled with serum. Characteristically, angiosarcomas create their own vascular space by dissecting through soft tissues. Distant metastasis, especially to the lungs and liver, is common. In other domestic animals, these tumors do not appear to behave as aggressively, and postexcisional recurrence rather than metastasis is more common. For all species, wide excision is the treatment of choice. Solar-induced canine
cutaneous hemangiosarcomas generally do not have an aggressive biologic behavior, although numerous lesions may continue to appear over a period of several years. Superficial lesions are easily controlled with topical cryotherapy as needed. Avoidance of further sun injury may reduce the development of new lesions. Recently, adjuvant chemotherapy consisting of vincristine, doxorubicin, and cyclophosphamide has been reported to shrink angiosarcomas; however, the effects of chemotherapy
for systemic control or radiation therapy for local control and longterm survival remain to be defined. The role of NSAID such as thalidomide and piroxicam are still not completely understood and may vary from drug to drug. Investigators are hoping to use antiangiogenic or angiostatic compounds such as canine canstatin that attack the blood supply of tumors to control and prevent metastases; however, results of clinical trials are pending. |
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