Veterinary Oncology: Canine Hemangiosarcoma

Hemangiosarcoma Overview

• Hemangiosarcoma (HSA) is a cancer originating from endothelial cells.
• The exact cause of HSA isn't fully understood, but exposure to UV light is strongly linked to dermal HSA in dogs.
• Approximately 50% of canine HSA cases have mutations in the PTEN tumor suppressor gene.
• High levels of VEGF, a pro-angiogenic peptide, are frequently observed in HSA.

Objectives for the Lecture

• Students will learn the anatomical locations of canine hemangiosarcoma.
• Students will understand the biological behavior of canine hemangiosarcoma.
• Students will be able to differentiate between potential diagnoses for a ruptured splenic mass in a dog.
• Students will be able to create a diagnostic and staging plan for a patient with hemangiosarcoma.
• Students will be able to determine the prognosis of cutaneous, splenic, and cardiac hemangiosarcoma cases.

Anatomic Sites

• Spleen is a common location for HSA.
• Skin is a less common location for HSA.
• Right atrium/auricle is a less common location for HSA.
• Liver is a less common location for HSA.
• Bone is a rare location for HSA.
• Retroperitoneal is a rare location for HSA.

Biological Behavior

• HSA is highly invasive locally.
• HSA is highly metastatic, often spreading to lungs, liver, regional lymph nodes, and omentum/mesentery.
• Stage 1 cutaneous HSA is an exception and tends to be less metastatic.
• HSA is a rapid-growing tumor, common in dogs, and a common cause of brain tumors in dogs.

Signalment

• Older dogs are more prone to HSA.
• Breeds such as German Shepherds, Goldens, and Labradors are overrepresented in HSA cases.
• Cutaneous HSA cases are often seen in lightly haired, lightly pigmented dogs who frequently sunbathe.

History

• HSA symptoms range from mild lethargy and inappetence to collapse and hypovolemic shock.
• Intermittent periods of lethargy or collapse can occur in days to weeks along with recovery periods.
• Cutaneous HSA lesions are often red, ulcerated, and prone to frequent bleeding.

Physical Exam

• Physical examination findings may be normal.
• Cranial organomegaly with a palpable mass can occur.
• Signs of acute to chronic blood loss—such as pale mucous membranes, weak or bounding pulses, tachycardia, and low body temperature—can be observed.
• Muffled heart sounds indicating pericardial effusion might appear.
• Cutaneous or subcutaneous masses should be noted.

Hemoabdomen/Splenic Mass Management

• Prioritize stabilizing the patient.
• Order bloodwork.
• Perform abdominocentesis or pericardiocentesis.
• Order imaging studies.

Diagnosis

• Stabilize the patient.
• Perform blood work (CBC, including cell counts, thrombocyte counts, chemistry profile).
• Consider potential causes of anemia (regenerative vs. non-regenerative).
• Monitor for schistocytes and liver function.
• Assess clotting times.
• Check for findings suggestive of disseminated intravascular coagulation (DIC).
• Perform abdominocentesis or pericardiocentesis.
• Perform imaging (ultrasound guided or blind abdominocentesis, radiographs, CXR, echocardiography, CT/MRI).
• Fluid cytology from samples is typically not helpful due to hemodilution.

Diagnostic Imaging (Site Dependent)

• Radiographs (AXR) may reveal peritoneal effusion, cranial abdominal mass effect, and/or globoid heart (less helpful for diagnosis).
• They also help rule out distant metastasis.
• Abdominal ultrasounds are important for evaluating masses and staging.
• Echocardiography is essential for assessing cardiac involvement.
• Cross-sectional scans such as CT/MRI can provide comprehensive information about the extent of disease.

Splenic Mass Differential Diagnosis

• Potential diagnoses include benign tumors such as hematoma and hemangioma and malignant tumors like hemangiosarcoma (HSA).
• The double 2/3 rule for differentiating between benign and malignant masses in the spleen can aid in initial estimates.
• In that rule, two-thirds of the malignancies found in splenic masses are indeed HSA.
• Also, about 70% of incidentally noted splenic nodules are benign.
• The definitive diagnosis is histopathology.

Clinical Staging System for Canine Hemangiosarcoma

• Table 33-2 outlines the stages of canine hemangiosarcoma based on primary tumor, regional lymph nodes, and distant metastasis.

Staging

• CXR/CT (3-view chest radiographs or thoracic CT)
• Abdominal ultrasound (AUS)
• Echocardiography
• Abdominal exploratory surgery with biopsy of any abnormalities for confirmation

Staging (Continued)

• Abdominal ultrasound (AUS) or CT for complete staging
• Key organs include spleen, liver, lymph nodes, omentum, mesentery, and other sites (kidney, retroperitoneum) to evaluate for metastasis.
• Nodules in older dogs aren't always metastatic.

Treatment (Surgery)

• Removal of the splenic mass (splenectomy).
• Removal of cutaneous masses based on margins (2-3 cm, 1 fascial plane deep).
• Rare resectability of right auricle masses (pericardectomy, to prevent tamponade).

Treatment (Radiation Therapy)

• Palliative protocols for cardiac HSA.
• Radiation impact is relatively unknown due to the heart's movement.
• High radiation doses difficult to administer due to the difficulty targeting the tumor precisely with the heart moving.

Treatment (Chemotherapy)

• Best outcome is surgery combined with chemotherapy.
• Stage I cutaneous HSA is an exception where chemo alone might suffice.
• Doxorubicin is the drug most used, IV administered every 2-3 weeks for 5 doses.
• Chemotherapy alone is not beneficial for splenic HSA.
• Doxorubicin improves survival for cardiac HSA.

Complementary and Alternative Therapies

• Yunan Baiyao (herbal remedy): mechanisms are unclear, but it may enhance surface glycoprotein expression on platelets and potentially be mildly cytotoxic against HSA cells.
• Aminocaproic acid and tranexamic acid both prevent fibrinolysis, helping with bleeding episodes.
• Polysaccaropépetide (turkey tail mushroom): anti-tumor activity in vitro, but some toxicity concerns exist; additional research is needed for further conclusions.

Follow-up

• Splenic HSA: AUS and CXR every 2-3 months.
• Cutaneous HSA: q3m PE and restaging (AUS/CXR).
• High risk factors include further lesion development (regular PE), metastasis, and local recurrence.
• Patient care is site/treatment dependent.

Prognosis (Bleeding Splenic Mass)

• Stage 2: surgery alone (1-3 months), surgery + chemo (4-6 months), Stage 3 (short duration—usually weeks).
• Stage 2 Cutaneous (completely excised): stage 1, not invasive into subQ (good prognosis >2 years), stage 2, invasive into subQ (good with aggressive treatment like surgery + chemo up to 18 months).

Prognosis (Cardiac)

• Surgery (rare) + chemotherapy (~6 months).
• Chemotherapy alone (~3-6 months).
• Radiation therapy (RT) is typically TBD.

Feline HSA

• Most common locations: skin or SQ, abdominal.
• Skin/SQ lesions are similar to other soft tissue sarcomas (STS).
• Splenic HSA behavior is comparable to canine cases.