Mast cell tumors in cats can present in two different forms: cutaneous and visceral. Cutaneous mast cell tumor is the most common and is the second most prevalent type of malignant cancer in cats. Visceral mastocytoma occurs mainly in the spleen, although it can also occur in other locations such as the intestine.
The diagnosis is made by cytology or biopsy, in cases of cutaneous mastocytoma, and by cytology, blood tests and diagnostic imaging in visceral mastocytoma. Treatment is by surgery in both cases, although in certain types of visceral mastocytoma it is not indicated, using chemotherapy and support drugs to improve the quality of life of the cat with mastocytoma. Keep reading this article on our site to learn more about mastocytoma in cats, its symptoms, treatment and prognosis.
What is mastocytoma in cats?
Mast cell tumor is a tumor that consists of an exaggerated multiplication of mast cells Mast cells are cells that originate in the bone marrow from hematopoietic precursors and can be found in the skin, connective tissue, gastrointestinal tract, and respiratory tract.
They are some defensive cells of the first line against infectious agents and their granules contain substances that mediate allergic and inflammatory reactions, such as histamine, TNF-α, IL-6, proteases, etc.
When a tumor occurs from these cells, the substances contained in their granules are released excessively, causing local or systemic effects that they can give rise to many different clinical signs, depending on their location.
Types of mastocytoma in cats
In cats, mastocytoma can be cutaneous, when it is located on the skin; or visceral, when it is found in the internal viscera.
Cutaneous mastocytoma
It is the second most common malignant tumor in cats, and the fourth among all feline tumors. Siamese cats seem more predisposed to cutaneous mast cell tumors. There are two forms of cutaneous mast cell tumors according to their histological characteristics:
- Mastocytic: occurs especially in cats over 9 years of age and divides compactly (the most frequent and benign, up to 90 % of cases) and diffuse form (more malignant, infiltrating and causing metastasis).
- Histiocytic: This occurs between ages 2 and 10.
Visceral mastocytoma
These mast cell tumors can be found in Parenchymal organs such as:
- Spleen (most frequent).
- Small intestine.
- Mediastinal lymph nodes.
- Mesenteric lymph nodes.
They especially affect older cats between 9 and 13 years old of age.
Symptoms of mastocytoma in cats
Depending on the type of mast cell tumor in cats, the symptoms may vary, as we will see below.
Symptoms of Cutaneous Mastocytoma in Cats
Cutaneous mast cell tumors in cats can be single or multiple masses (20% of cases). They can be found on the head, neck, chest or extremities, among others.
Consists of nodules which are usually:
- Defined.
- 0, 5-3 cm in diameter.
- Not pigmented or pink.
Other clinical signs that may appear in the area of the tumor are:
- Erythema.
- Superficial ulceration.
- Intermittent itching.
- Self-trauma.
- Inflammation.
- Subcutaneous edema.
- Anaphylactic reaction.
Histiocytic mast cell nodules usually disappear spontaneously.
Symptoms of Visceral Mastocytoma in Cats
Cats with visceral mast cell tumors exhibit signs of systemic disease such as:
- Vomiting.
- Depression.
- Anorexy.
- Weightloss.
- Diarrhea.
- Hyporexia.
- Respiratory difficulty if there is pleural effusion.
- Splenomegaly (enlarged spleen).
- Ascites.
- Hepatomegaly (enlarged liver).
- Anemia (14-70%).
- Mastocytosis (31-100%).
When a cat presents alterations in the spleen, such as an increase in size, nodules or general involvement of the organ, in the first place to think about is a mast cell tumor.
Diagnosis of mastocytoma in cats
The diagnosis will depend on the type of mast cell tumor that the veterinarian suspects the feline may have.
Diagnosis of Cutaneous Mastocytoma in Cats
Cutaneous mastocytoma in cats is suspected when a nodule with the characteristics described above appears, confirmed by cytology or biopsy.
Histicitic mast cell tumor is the most difficult to diagnose by cytology due to its cellular characteristics, vague granularity and the presence of lymphoid cells.
It must be taken into account that mast cells can also appear in feline eosinophilic granuloma, which can lead to a erroneous diagnosis.
Diagnosis of visceral mastocytoma in cats
The differential diagnosis of feline visceral mastocytoma, especially that of the spleen, includes the following processes:
- Splenitis.
- Accessory spleen.
- Hemangiosarcoma.
- Nodular hyperplasia.
- Lymphoma.
- Myeloproliferative disease.
CBC, biochemistry and imaging tests are key to diagnosing visceral mast cell tumor:
- Blood test: in the blood test, mastocythemia and anemia may raise suspicion. Especially the presence of mastocythemia, being characteristic of this process in cats.
- Abdominal ultrasound: Abdominal ultrasound can detect splenomegaly or an intestinal mass and look for metastases in mesenteric lymph nodes or other organs, such as the liver. It also allows to see alterations in the parenchyma of the spleen or nodules.
- Thoracic X-ray: The chest X-ray allows the state of the lungs to be observed, looking for metastases, pleural effusion or alterations in the cranial mediastinum.
- Cytology: Fine-needle aspiration cytology of the spleen or intestine can differentiate a mast cell tumor from other processes described in the differential diagnosis. If performed on pleural or peritoneal fluid, mast cells and eosinophils can be observed.
Treatment of mastocytoma in cats
The treatment to be followed will also present some variations depending on the type of mast cell tumor to be treated.
Treatment of cutaneous mastocytoma in cats
Treatment of cutaneous mast cell tumors is performed with removal surgery, even in cases of histiocytic forms, which tend to regress from spontaneously.
Surgery is curative and must be performed by local resection, in mast cell cases, and with more aggressive margins in diffuse cases. In general, Local excisionwith margins between 0.5 and 1 cm is suggested for any cutaneous mast cell tumor diagnosed by cytology or biopsy.
Recurrences in cutaneous mast cell tumors are very rare, even in incomplete excisions.
Treatment of visceral mastocytoma in cats
Surgical removal of visceral mastocytoma is performed in cats with an intestinal or spleen mass without metastases elsewhere. Before removal, the use of antihistamines such as cimetidine or chlorferamine is advised to reduce the risk of mast cell degranulation, which would cause problems such as gastrointestinal ulcers, abnormalities of coagulation and hypotension.
The median survival time after splenectomy is between 12 to 19 months, but negative prognostic factors are found in cats with anorexia, with considerable weight loss, with anemia, mastocythemia and metastasis.
After surgery, adjunctive chemotherapywith prednisolone, vinblastine, or lomustine is usually given.
In cases of metastasis or systemic involvement, oral prednisolone can be used at doses of 4-8 mg/kg every 24-48 hours. If an additional chemotherapeutic agent is needed, chlorambucil can be used orally at a dose of 20 mg/m2 every two weeks.
To improve the symptoms of some cats, antihistamine drugs can be used to reduce excessive gastric acidity, nausea and the risk of of gastrointestinal ulcer, antiemetics, appetite stimulants or analgesics.
