Mast Cell Tumor (Mastocytoma) in Cats

Mast cell tumors do not present a life-threatening emergency, but early identification and treatment improves the odds for a good outcome.

A mast cell tumor diagnosis has a big impact on both the cat and its family because treatment is often invasive and time-consuming.

Mast cell tumors are the second-most common skin tumor in cats. The majority of mast cell tumors on the skin are benign while those on the spleen or intestines tend to be malignant. They are more common in older (10+ years) and Siamese cats.

The secondary symptoms vary based on the localization of the tumors.

Secondary symptoms of cutaneous mast cell tumors include:.

• Hard, small, hairless lumps on the skin
• Often solitary but may occur in multiples
• Excessive itchiness around the tumor
• Red skin around the tumor
• Ulceration

Symptoms vary in severity based on the progression of the tumor and whether or not it has metastasized.

The cause of mast cell tumors is not fully understood but appears to be a combination of genetic and environmental factors.

Symptoms vary slightly depending on the location of the tumor(s).

Cutaneous mast cell tumors: The primary symptom is a mass on the skin. Cutaneous (skin) tumors are primarily seen around the head, neck, limbs, and tail. These can appear as a single mass or several.

Visceral tumors are within the body and tend to appear on the spleen, intestines, and liver. These typically escape detection until metastasis occurs and non-specific symptoms like vomiting or appetite loss occur.

After a physical examination and medical history, a number of tests can confirm a mast cell tumor and assist in determining the stage of cancer, including:

• Fine needle aspiration of the tumor
• Biopsy
• Bloodwork and urinalysis
• Diagnostic imaging (x ray, ultrasound)

Treatment depends on the location, severity, and staging of the tumor. Supportive treatment involves symptom management for allergic responses as the removal of the tumor may release a large amount of histamines into the body, mimicking an allergic reaction.

If the tumor is benign and cutaneous, surgical excision is the primary treatment and shows a good prognosis post-surgery. If the tumor is malignant, poorly defined, or in an area difficult to ensure full surgical removal, radiation therapy and chemotherapy can be used to reduce mass growth and lower the risk of metastasis.

If the tumor is in a late stage of development and is malignant, most treatment options are palliative and may include euthanasia.

Benign cutaneous tumors have a good prognosis with successful surgical removal. Approximately 90% of cats are healthy and alive 4 years after treatment. Recurrence is rare and seen in cases of tumors where it is difficult to fully remove all of the tissue around the tumor.

Visceral mast cell tumors tend to be malignant and have a poor prognosis. Surgery is not always possible and radiation and chemotherapy are the next option. Radiation can help to reduce spread and shrink the tumor while chemotherapy is mostly palliative.

Mast cell tumors are not preventable but the risk of serious consequences can be reduced with regular check ups and monitoring for skin abnormalities. Mast cell tumors are not contagious.

This is the second-most common form of skin tumors in cats. Malignant and visceral tumors are less common in cats.

• Surgical excision
• Radiation
• Chemotherapy
• Palliative care
• Symptom management (allergen treatments)