Diagnosis of Mast Cell Tumor

If your DVM veterinarian suspects that your cat may have a mast cell tumor, the following steps may be taken.

• Detailed History Taking
  • Your vet will discuss every aspect of your cat’s condition and overall health care. There are other causes of the same types of signs as mast cell tumor, and this history will help to differentiate the various possible causes.
  • If there is a lump, when did it appear? How rapidly has it been growing?
• Physical Examination
  • Your veterinarian will check your cat over carefully, all over. This will include palpating your cat’s body, feeling for any unusual lumps or bumps, both internal and external.
  • Your cat’s superficial lymph nodes will be checked for any enlargement. Any abnormalities at all will be noted, and may be helpful towards making a diagnosis and staging of a mast cell tumor.
• Routine Blood and Urine Tests
  • As part of a minimum database when working up a sick cat, vets often carry out routine blood work, including the usual panel of diagnostic tests, such as hematology (complete blood count) and biochemistry profiles.
  • Full urinalysis will also usually be undertaken. These tests are a useful way of checking for any other underlying illnesses, and the results act as a useful baseline, even if no abnormality is found.
• Specialized Blood Tests
  • Your veterinarian may recommend specific blood tests for some viral infections such as FeLV and FIV, since there are significant implications if your cat is positive for either of these.
• Diagnostic Imaging
  • Radiography (x-rays) and abdominal ultrasound may be carried out, to examine your cat’s internal organs for possible spread of mast cell tumors, and to screen your cat for other internal diseases.
  • These investigations are not just important for making the initial diagnosis: they are also part of the staging process, searching for any evidence of metastases which would help with decision making around treatment plans.
• Biopsies
  • • If an abnormal mass is located (whether in the skin, or internally), a biopsy (sample of living tissue) is the only way that a mast cell tumor can be definitively diagnosed. This usually involve a Fine Needle Aspirate (FNA), which is how a diagnosis of mast cell tumor is usually made.
    • Cytology will be carried out these fine needle aspiration samples, with a pathologist examining the samples, checking for high levels of mast cells.
    • Sometimes, an initial sample may simply confirm the broad diagnosis of “mast cell tumor” and a second, larger, biopsy sample (e.g. a core biopsy, or an excisional biopsy, by excision of the entire tumor) may be needed for full histopathology, to discover more detailed information about the nature of the mast cell tumor.

Grade

Mast cell tumors are usually graded, from low grade to high grade, but the system of classification in cats is far less detailed than that used for canine mast cell tumors.