
Hemangiosarcoma of the third eyelid (image source: Multari et al. 2002)
Feline Hemangiosarcoma
Feline hemangiosarcoma (HSA) is a malignant tumor of the blood vessel walls. It originates from the endothelial cells that line the surface of blood vessels of the entire circulatory system. It is a rare but very aggressive tumor that metastasizes early, resulting in a poor prognosis. This page is about feline hemangiosarcoma, its types, signs and symptoms, diagnosis, treatment and prognosis.
Types of Hemangiosarcoma

Cutaneous Hemangiosarcoma
Cutaneous HSA often develops on the cat’s lightly haired areas such as the head and ears. It is more prevalent among older cats with lightly pigmented skin. This is due to the reported link between sun exposure and cutaneous HSA development. Tumors can manifest as individual or multiple skin masses with red to purple coloration.

Visceral Hemangiosarcoma
Visceral HSA affects the spleen, heart, liver and other internal organs. It has a high metastatic potential and very aggressive, thus it is associated with a poor prognosis. Anemia or internal bleeding are the common signs of visceral HSA in cats (Culp et al., 2008).

Subcutaneous Hemangiosarcoma
This subtype of feline hemangiosarcoma is characteristically found under the skin of cats so they are often mistaken for other types of cysts or tumors. Subcutaneous HSA can be locally invasive like cutaneous forms of HSA. However, subcutaneous HSA is more likely to metastasize and recur than cutaneous HSA (Johannes et al., 2007).

Nasal Planum Hemangiosarcoma
Nasal planum HSA is a tumor common to middle-aged or older cats. It presents as a mass on the nasal planum with deformities, bleeding and associated eye problems (McGrath et al., 2022).
Signs and Symptoms
Depending on the location of the feline hemangiosarcoma, cats may present various clinical signs. Lethargy is a common sign among cats with the tumor. Visceral HSA may cause cats to develop anemia and weakness due to internal bleeding. Internal bleeding may also lead to fluid accumulation and abdominal distention. Cats with HSAs that affect the thoracic cavity or lungs may present with respiratory distress such as difficulty breathing. Visible lesions on the skin are a hallmark of cutaneous HSA.
Diagnosis

Clinical Exam
When diagnosing cats for HSA, veterinarians look for the following signs and symptoms: anemia, shock, skin lesions, abdominal masses or fluid accumulation which are specific to the type of feline hemangiosarcoma being suspected.

Imaging
Abdominal ultrasound is an imaging technique typically used to detect masses in internal organs such as the spleen and liver. It can also be used to identify internal bleeding through the presence of free fluid. Metastasis can be detected using X-rays of the lungs and other thoracic structures.

Histopathology
Histopathology is usually needed to come up with a definitive diagnosis for feline hemangiosarcoma. To obtain tissue samples, a biopsy or fine needle aspiration is performed. Analysis involves identification of atypical spindle cells which are a characteristics of HSA.
Treatment

Surgery
For cutaneous HSA and other localized tumors, surgical resection is a recommended treatment procedure. Complete and clean resections can lead to good outcomes for these tumors. For visceral HSA affecting the spleen, a splenectomy is typically recommended. High risk of metastasis for this tumor form means long-term survival cannot be guaranteed.

Chemotherapy
Doxorubicin has been used to treat feline HSAs as well as other types of tumors in cats although efficacy of this drug against feline HSA has not been established. Some publications have reported promising results when drugs such as vincristine and cyclophosphamide were used in combination.

Prognosis
Cutaneous HSAs typically have better prognosis than visceral HSAs. However, prognosis for different feline HSAs still depend heavily on the metastatic level, overall health of the cat and its response to treatment.
Available Services for
Characterization
FACS (fluorescence-activated cell sorting)
qPCR (quantitative Polymerase Chain Reaction)
RNAseq (RNA sequencing)
Sterility
HLA (human leukocyte antigen) typing
More on request
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