Canine Subcutaneous & Cutaneous Hemangiosarcom

Oncology Update

Central Toronto Veterinary Referral Clinic

Kevin Finora DVM, Diplomate ACVIM (Oncology and Small Animal Internal Medicine)

Cutaneous and Subcutaneous Hemangiosarcoma

Cutaneous and Subcutaneous HemangiosarcomaEmerging diseases are both interesting and frustrating. Cutaneous and subcutaneous manifestations of hemangiosarcoma (HSA) have been previously reported in the literature, but there appears to be an increase in the incidence of these diseases. The reasons are unclear. It could be veterinarians are more aware and doing a better job with work-up, increased environmental exposure to the sun or changing genetics.

Cutaneous and subcutaneous HSA have some similarities but can behave very differently. Solar radiation is a known risk factor and dogs with short hair coats and lightly pigmented skin are 66% more likely to develop the cutaneous form than dogs with longer hair coats. Hair coat length and skin colour are not associated with the incidence of the subcutaneous form.

Cutaneous HSA tend to be small and are commonly seen on the ventral abdomen. They occur within the dermis only and do not reach into the subcutaneous tissue. Cutaneous HSA tends not to spread and appears to be less malignant than visceral HSA. In fact, the degree of malignancy of HSA decreases as you move out from the viscera. Splenic HSA is most malignant, followed by HSA of muscle, then subcutaneous HSA and finally cutaneous HSA. Cutaneous HSA is often identified as a red to pink mass associated with the skin. Diagnosis with cytology is difficult as typically only blood will end up in the needle. In most cases a biopsy is needed in order to make the diagnosis. The treatment of choice for cutaneous HSA is surgery to remove the entire tumour. Typically the cutaneous lesion will be the primary lesion. However, metastatic spread from a primary visceral tumour is possible and as such full staging to include three view thoracic radiographs and abdominal ultrasound is indicated. If no evidence of metastasis is found then the lesion(s) should be removed with 1-2 cm surgical margins. The role of chemotherapy is unknown for the cutaneous form. Hemagiosarcoma is a tumour of blood vessels and circulating blood has been in direct contact with the neoplastic cells. Therefore, it is possible for microscopic metastatic behaviour to occur. As such, my recommendation, to be most aggressive in fighting the cancer, is to treat with adjunctive chemotherapy. Survival times beyond that expected for splenic HSA is likely. Survival times of 780 days for dogs with cutaneous HSA treated aggressively with surgery and chemotherapy have been reported.

Subcutaneous HSA is a more complex disease. It tends to be more aggressive than the cutaneous form. The approach for subcutaneous HSA is as noted above with staging, to be followed by surgery. Local control of this tumour can be difficult. In some cases the subcutaneous lesion will appear extensive. Often these tumours will have bled into the subcutaneous space. This bleeding results in a very large and often bruised mass or swelling noted under the skin. The challenge is to identify the extent of the lesion to be removed. In some instances the lesion can be easily identified and surgery is possible. In others, it is nearly impossible to identify the actual tumour. Unfortunately if the tumour is sufficiently large and cannot be clearly delineated, surgery is not possible. A significant post-operative complication for incompletely resected subcutaneous HSA is continued subcutaneous bleeding. The degree of bleeding can be significant and may lead to severe and even life threatening anemia. In cases where the lesion can be removed with surgery, follow-up chemotherapy is recommended. I will recommend following up after chemotherapy with some form of anti-angiogenic therapy. Survival times are poorly reported but appear to fall somewhere between 172 and 307 days.

The more challenging situation is how to address a subcutaneous HSA presenting as an amorphous and bleeding subcutaneous mass. Various approaches have been suggested including chemotherapy, radiation therapy and anti-angiogenic therapy. No one therapy has been demonstrated to be more successful than the next and no data exist which offer such a comparison. My usual approach it to treat palliatively with chemotherapy and concurrent NSAID therapy (for the anti-angiogenic effects). Unfortunately therapy is usually not successful and survival times rarely reach beyond 2-4 months.


Dr. Kevin Finora is a Board Certified Oncologist and Small Animal Internist who is part of the Healthcare Team at the Central Toronto Veterinary Referral Clinic. He is available for referrals and consultations Monday to Thursday (including Monday and Tuesday evenings). Please contact him with any oncology questions or concerns.

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