Hemangiosarcoma

Overview

• Hemangiosarcoma is an aggressive, malignant tumor originating from blood vessels, most commonly affecting the spleen but also found in the heart, liver, and other vascular-rich tissues.

• This tumor is a significant cause of hemoperitoneum (abdominal bleeding) and can lead to sudden hypovolemic shock in affected dogs.

• Hemangiosarcoma metastasizes quickly, with the liver and lungs being the most frequent sites of secondary spread.

• While surgical intervention can improve survival and quality of life, the prognosis remains poor, with a 1-year survival rate of less than 10% regardless of the treatment approach.

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Etiology

• The exact cause of hemangiosarcoma remains unknown, but it is recognized as a malignant cancer of blood vessels. This tumor is highly vascular and friable, making it prone to rupture, which leads to internal bleeding.

• Hemangiosarcoma typically arises in the spleen, but can also develop in visceral organs like the liver or heart.

• The condition is seen more commonly in large-breed dogs, especially German Shepherds, Golden Retrievers, and Labrador Retrievers, suggesting a genetic predisposition. However, any breed can be affected.

• Breed Predisposition: German Shepherds, Golden Retrievers, Labrador Retrievers

• Age: Most commonly affects middle-aged to older dogs.

• Metastasis: Highly metastatic to liver, lungs, and occasionally to other organs.

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Clinical Signs​

• Clinical signs may be subtle or acute, and include:

  • Non-specific symptoms:

    • Lethargy, decreased appetite, and gastrointestinal distress.

  • Acute collapse or shock:

    • In some cases, the tumor ruptures, causing internal bleeding, which leads to hypovolemic shock. Affected dogs may show signs of acute collapse, pale mucous membranes, and weak pulse.

  • Abdominal signs:

    • Abdominal distension or pain due to hemoabdomen (blood in the abdomen).

  • Incidental discovery:

    • Occasionally, the mass is found during routine physical exams or imaging (such as abdominal ultrasound or radiographs) with no clinical symptoms.

  • Breed and Age Risk:

    • Large-breed dogs and those between 7–10 years of age are at higher risk.

  • Metastasis Symptoms:

    • Dogs with metastasis may show signs related to affected organs, such as respiratory distress (if the lungs are involved) or jaundice (if the liver is involved).

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Diagnosis​

• Physical Examination:

  • Palpation of the abdomen may reveal a firm splenic mass or signs of hemoabdomen.

• Bloodwork:

  • A complete blood count (CBC) and chemistry panel help assess the patient's overall health and identify anemia, thrombocytopenia, or signs of coagulopathy. These can raise suspicion for malignancy.

• Coagulation Tests:

  • Prothrombin time (PT) or activated partial thromboplastin time (aPTT) to check for a coagulopathy, which occurs in about 50% of dogs with hemangiosarcoma.

• Imaging:

  • Chest radiographs (3 views) to assess for pulmonary metastasis, as 50% of dogs with splenic hemangiosarcoma have lung metastases at the time of diagnosis.

  • Abdominal ultrasound to confirm the presence of a splenic mass, assess for effusion, and evaluate for metastasis in other abdominal organs. It can also help determine the mass architecture, which may influence the decision to perform fine-needle aspiration (FNA).

• Electrocardiogram (ECG):

  • Arrhythmias are common in dogs with hemangiosarcoma, particularly those with right atrial involvement, but pre-surgical echocardiography is not routinely recommended unless there is concern for cardiac masses.

• Histopathology:

  • Definitive diagnosis requires a tissue biopsy obtained after splenectomy or from suspicious metastatic lesions. Histopathology is essential to confirm the diagnosis, as clinical and imaging findings cannot reliably differentiate hemangiosarcoma from other malignancies.

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Treatment

• Treatment for hemangiosarcoma typically involves a combination of surgical intervention and chemotherapy, though prognosis remains guarded.

• Surgical Treatment:

  • Splenectomy (surgical removal of the spleen) is the first line of treatment for splenic hemangiosarcoma. The entire spleen should be removed, along with any suspected metastatic lesions in the abdominal cavity.

  • Perioperative considerations:

    • Surgeons must take care to minimize the risk of iatrogenic tumor seeding by thoroughly lavaging the abdomen and using fresh gloves and instruments for closure.

    • Dogs with ruptured tumors may require emergency surgery to control hemorrhage and stabilize the patient.

• Chemotherapy:

  • Following surgery, chemotherapy is used to control systemic disease and extend survival.

  • The most commonly used chemotherapy drug is doxorubicin, administered as part of a multi-agent protocol.

  • Due to cardiotoxicity, the number of doxorubicin treatments may be limited.

  • Emerging metronomic chemotherapy protocols (low-dose chemotherapy) are being studied to enhance survival without the side effects of traditional protocols.

• Palliative and Supportive Care:

  • For dogs with metastatic disease or those who are not candidates for surgery, palliative care may include medications like Yunnan Baiyao (to control hemorrhage) and polysaccharopeptide mushrooms (to slow tumor growth and improve quality of life).

  • Electrocardiographic monitoring is recommended during and after surgery, as arrhythmias are common and can increase perioperative mortality.

• New and Investigational Therapies:

  • New treatments are under investigation, including eBAT (a novel drug for treatment and prevention of hemangiosarcoma) and Losartan (an angiotensin II blocker), which may have anti-tumor effects.

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Prognosis

• The overall prognosis for dogs with hemangiosarcoma remains poor, despite treatment.

• Surgical intervention can provide palliative relief and control acute hemorrhage, with an average survival time of 1 to 3 months.

• When chemotherapy follows surgery, survival may extend to 6 to 9 months.

• Long-term survival is rare, and 1-year survival is less than 10%.

• Non-ruptured tumors and low-grade lesions have a better prognosis compared to ruptured or high-grade tumors.