The Great Pretender

Tigger is a 6 year old Boxer dog who came to see us in May. She is a gorgeous pooch, very happy in herself and well in every respect.

She had a small, inocuous lump on the skin on her tummy and another near her lady bits, the latter of which was ulcerated and bled a little – she may have caught it on something. We treated her with a short course of antibiotics, in case the lumps were just infected cysts, but the growths didn’t change.

As they were small lumps we chose to remove them surgically. The option would have been to take fine needle aspirates first, to see if a pathologist could identify the cell types on a slide. Because we weren’t sure exactly what they were, and although they looked quite innocent, we removed them with very wide margins, just in case.

Tigger recovered really well from her surgery and the wounds soon healed up. We sent her home with plenty of pain killers to keep her comfortable.

We sent the lumps to a pathologist to identify them histologically. The results said that the lumps were mast cell tumours, that, thankfully, had been completely removed, with good margins of normal tissue around them. Mast cell tumours are a potentially malignant form of cancer that are defined in grades of 1 (benign) to 5 (very malignant with a poor outcome).

Tigger’s lumps proved to be Grade 2 Mast Cell tumours. The pathologist recommended further tests, as some grade 2 tumours can behave aggressively (by spreading to other organs and recurring at the surgical site).

Some special stains were used to do something called immunohistochemistry, looking for cells which stain positive for something known as Ki67. We can tell a lot about tumour behaviour with special stains and tests. The number of Ki67  ‘positive’ mast cells was extremely low so Tigger was given an excellent prognosis and we are just going to monitor the surgical site. Hopefully, Tigger should live happily ever after but we will continue to monitor for any new lumps that appear anywhere and deal with them hastily.

Sometimes we see such cases and the patients aren’t so lucky. With more aggressive mast cell cancers we need to do imaging (xrays / scans) to look for evidence of spread, take samples from the spleen and liver to look for spread and treat the patients with chemotherapy (various regimes are available depending on the type of mast cell tumour it is and whether it has metastasized).

They call Mast Cell Tumours the ‘Great Pretender‘. Some look like very benign skin tumours that could be mistaken for an innocent cyst. Some look like fatty lumps under the skin, which could be mistaken for lipomas (benign tumours that grow in fat).

We recommend that all growths found on your pet are examined by the Veterinary Surgeon. Most skin tumours are benign, others less so. Early treatment for skin cancers is essential if we are aiming at saving lives. Please be vigilant.

Thankfully Tigger’s story had a really happy ending, but this isn’t always the case. Be assured though, that even in the more serious cases, there are often things we can do to help, ensure good quality of life, extend life and ensure freedom from pain.