Hemangiosarcoma in Cats: Causes, Symptoms, & Treatment

Hemangiosarcoma is an uncommon type of cancer found in cats. However, when it does occur, it is often highly aggressive and has a tendency to spread rapidly. This article will explore the various types of hemangiosarcoma seen in cats, methods for diagnosis, and available treatment options.

Quick Overview: Hemangiosarcoma in Cats

What is Hemangiosarcoma?

Hemangiosarcoma (HSA) is an uncommon type of cancer in cats, affecting only an estimated 1-2% of the feline population. This cancer targets endothelial cells, which form the inner lining of blood vessels.

Since blood vessels are present throughout the body, hemangiosarcoma has the potential to develop anywhere and can spread easily to various organs through the bloodstream.

However, while it can occur in any location, certain patterns are observed regarding where it tends to develop in animals. In dogs, for instance, it most commonly originates in the spleen or the right atrium of the heart.

Cats, on the other hand, exhibit distinct patterns of hemangiosarcoma development that differ significantly from those seen in dogs. Below are the typical forms of this cancer in cats and their characteristics.

Cutaneous/Subcutaneous

The cutaneous and subcutaneous layers of the skin are distinct, but they are often grouped together in studies on hemangiosarcoma in cats. This type of cancer is thought to be the most frequently observed in cats, although this could be due to external tumors being more noticeable compared to internal ones. Cutaneous tumors, located on the skin’s surface, are generally more favorable for surgical removal. Conversely, subcutaneous tumors, found beneath the skin, pose a greater risk of metastasis and are more challenging to completely excise through surgery. Additionally, hemangiosarcoma involving the eyes, such as in the conjunctiva, third eyelid, or corneal surface, has also been reported in cats.

Visceral

Visceral pertains to internal organs. In cats, hemangiosarcoma is most frequently found in the spleen, liver, and intestines. It can also occur in areas such as the lymph nodes, the omentum (which connects the intestines), and the lungs. Although rare, the pancreas has also been identified as a site for this condition.

There is some debate about whether visceral hemangiosarcoma is less common than the cutaneous or subcutaneous types, or if it is simply more challenging to detect. However, it is widely accepted that the visceral form tends to be more aggressive and spreads at a faster rate.

Oral

Oral hemangiosarcoma in cats is extremely uncommon, with limited data available on its prevalence. Among oral tumors in cats, squamous cell carcinoma is the most frequent, accounting for up to 80%, followed by fibrosarcoma, which makes up about 20%. A variety of other tumor types comprise the small remaining percentage, with hemangiosarcoma being one of the rarest.

Causes of Hemangiosarcoma in Cats

Research on hemangiosarcoma in cats is relatively limited compared to dogs, especially regarding the internal forms of this cancer. The exact causes remain unclear, but it is thought that both genetic predispositions and environmental influences may contribute. There doesn’t appear to be a gender-based difference in risk.

For skin-related forms of hemangiosarcoma, however, sun exposure seems to play a role. These cases are often found in areas that receive more sunlight, such as the scalp, ears, eye conjunctiva, muzzle, flank, and groin. Cats with lighter-colored skin, particularly in these areas, may face a higher risk.

While squamous cell carcinoma is the most common skin cancer in cats linked to sun exposure, similar risk factors may also apply to cutaneous hemangiosarcoma.

Signs of Hemangiosarcoma in Felines

Cutaneous

• Tumors are often small (0.1cm up to 1.0cm).
• Tumors have a red or purple colored appearance.
• Tumors most often occur on the head.
• Tumors most often occur in light-pigmented areas of skin.
• Tumors are usually not painful when touched.
• Skin surface tumors usually disrupt fur growth in their location (as opposed to subcutaneous).

Subcutaneous

Tumors of comparable size to cutaneous ones (ranging from 0.1 to 1.0 cm) tend to present as swellings just beneath the skin. The fur on the surface typically remains undisturbed. These may have a purplish-blue coloration, resembling a bruise or hematoma. Their location on the body is often consistent with that of cutaneous tumors.

Ocular

• Most common sites are the conjunctiva (beneath the lid), third eyelid, and cornea.
• Appears as a focal red fleshy type growth on the eye.
• Conjunctival growths may appear more as a focal eyelid swelling or where the eyelid appears “pushed out” because of the growth occurring beneath it.

Oral

Oral tumors can be very difficult to visually see in cats, even during a veterinary exam. In many cases, oral tumors can occur beneath the tongue or further back into the mouth where it’s hard to see. When a cat is showing signs of significant oral pain or discomfort, sedation is often needed to get a thorough assessment.

These are general signs where there is enough oral pain or discomfort for an oral tumor to be a potential concern:

• Excessive salivating or drooling
• Blood present in saliva or drool
• Chewing food with one side of the mouth
• Dropping food while eating
• Excessive swallowing or tongue movement
• Reduced to absent appetite (may be gradual or appear suddenly)
• Weight loss
• Signs of pain, tensing, or irritation even with gentle attempts to handle mouth or face
• Pawing at the mouth
• Foul breath odor

Visceral

Hemangiosarcoma in the visceral organs often remains unnoticed until a severe bleeding episode occurs. As this tumor develops in blood vessels, bleeding issues are highly prevalent, particularly when the spleen is involved.

The symptoms of visceral hemangiosarcoma are generally vague but relate to bleeding and abdominal discomfort. These may include:

– Fatigue or weakness
– Decreased appetite
– Vomiting, especially if the tumor ruptures and bleeds
– Difficulty breathing or rapid breaths
– Sudden collapse
– Pale gums
– Abdominal tenderness or tension
– Swelling or bloating in the abdomen

In cases where the tumor affects the intestinal tract in cats, there may be visible blood in their vomit or stools.

Tragically, some cats may show no signs of illness until sudden death occurs. One documented case involved a 15-year-old cat with pancreatic hemangiosarcoma that had spread throughout the abdominal region, despite no prior symptoms such as weight loss or illness.

Challenges Associated with Hemangiosarcoma in Felines

Metastasis, the process by which cancer spreads through blood or lymphatic systems to other parts of the body, is a frequent issue with hemangiosarcoma. Visceral hemangiosarcoma carries the highest risk of spreading since it is more challenging to detect early compared to cutaneous or subcutaneous forms.

The cancer most commonly spreads within the abdominal region, though it can also reach the lungs. In one study, approximately 30% of cats diagnosed with visceral hemangiosarcoma already had lung involvement at the time of diagnosis.

Another common problem is bleeding. While bleeding is usually less severe with skin-based hemangiosarcoma, internal bleeding poses a significant risk in cases of visceral hemangiosarcoma, particularly when major organs such as the spleen, liver, pancreas, or kidneys are affected.

Understanding Hemangiosarcoma in Felines

Determining hemangiosarcoma in cats can be challenging without a tissue biopsy. While this tumor type is commonly linked to the spleen and heart in dogs, making it easier to suspect based on imaging, cats often present with other more common tumors in areas like the skin, mouth, or abdomen.

Fine-needle aspiration, which involves collecting cell samples, is a less invasive diagnostic method than a biopsy and is frequently performed with ultrasound guidance. This approach can diagnose certain cancers, such as lymphoma, but it is often insufficient for confirming hemangiosarcoma. For definitive diagnosis, a tissue biopsy or surgical removal of the tumor is usually necessary.

For tumors located on or just beneath the skin, surgical excision is often both diagnostic and therapeutic. However, diagnosing and treating visceral hemangiosarcoma is more complex. If symptoms suggest this type of tumor, veterinarians typically recommend bloodwork and imaging like X-rays or ultrasounds to detect fluid or bleeding in the chest or abdomen. Ultrasound has been shown to identify tumor locations in about 75% of cases.

If imaging reveals potential tumors, fine-needle aspiration might be attempted if conditions allow, though it may not always yield a conclusive diagnosis. In such cases, a surgical biopsy could be considered, provided the cat’s condition allows for it.

Blood tests are a common initial step for severely ill cats but cannot specifically diagnose hemangiosarcoma. Anemia is frequently observed in cats with visceral hemangiosarcoma, and abnormal liver or kidney values may also appear if those organs are affected. However, lab results can often be nonspecific and require further context from other diagnostic tools.

Options for Managing Hemangiosarcoma in Felines

Surgery

The primary approach to treating hemangiosarcoma involves surgically removing the tumor, regardless of where it is located. For tumors on or just beneath the skin, efforts are typically made to excise the entire growth. However, this type of cancer has a significant likelihood of recurring, particularly when the tumor cannot be completely removed or when sufficient margins of healthy tissue around the tumor are not achieved.

Skin-based tumors generally have the highest success rate for complete surgical removal. A study found that nearly 75% of cats with cutaneous hemangiosarcoma had their tumors fully excised. In contrast, subcutaneous tumors are more challenging to remove entirely with clean surgical margins, and recurrence at the site of surgery is common. The same study reported that only one out of sixteen cases involving subcutaneous tumors achieved complete removal, with local recurrence rates estimated at approximately 60%.

Visceral hemangiosarcoma tends to have a much grimmer prognosis due to its difficulty in early detection and its rapid spread to other parts of the body. Many cats with this form of the disease are euthanized shortly after presenting with severe symptoms. In one study, about half of the cats underwent surgery for visceral hemangiosarcoma, but tumor removal was only attempted in a small number of cases due to the extensive nature of the disease in most patients.

Chemotherapy

Chemotherapy can be considered as a treatment option after surgery to help slow the progression of cancer, although it is rarely used in cats. In one study, only two cats underwent chemotherapy. While chemotherapy has shown improved survival times in dogs with HSA, there is insufficient data to determine its effectiveness in cats.

For cats diagnosed with visceral HSA, the median survival time is approximately 77 days, with a range between 23 and 296 days. Unfortunately, the prognosis for visceral HSA in cats is generally poor, and treatments are typically aimed at providing comfort rather than achieving a cure.

From personal observation, cats with a single large bleeding tumor in the spleen might benefit most from palliative surgery. Removing the spleen can address severe bleeding and improve the cat’s quality of life temporarily, though this improvement usually lasts only a few months at most.

Prevention of Hemangiosarcoma in Cats