Mast Cell Tumours In Dogs

Mast Cell Tumours (MCT’s) account for about 20% of skin tumours in dogs.  They can often be mistaken for fatty lumps under the skin called lipomas which are benign fat tumours.

MCT’s are usually within the skin, and move with the skin when palpated.  Mast Cells are immune cells containing large amounts of histamine and proteolytic enzymes which help defend the body from parasitic invaders and are activated in allergy type reactions.

They are graded 1-3 and staged 1-4.  The latter staging is based on whether the tumour has spread within the body such as the regional lymph nodes, lungs or liver.

It also tells us what we can expect the tumour to do and whether the dog needs further chemo or radiation treatment.  It helps us prognosticate the dogs’ future.  It is not fully understood what causes the tumour formation but they can occur in any age or breed.  However some breeds such as Boxers, Pugs, Retrievers, Boston Terriers, English Bulldogs and other brachiocephalic breeds seem to be more prone.

Their benign appearance makes them a dangerous tumour, as they are often overlooked or ‘fobbed off’ as just a lump of no real consequence.  However sometimes they take on an ulcerated appearance.  So any lump in your dogs skin, especially one that moves with the skin when palpated should be investigated.

Often a quick FNA (Fine Needle Aspirate) stained and examined quickly at the time of the consultation will give you an answer if it’s a MCT or not.

At our Hospital we see on average 5 a month.  Some with a very sad outcome because they have been left too long before removal.  As far as we are concerned any skin lumps are deemed guilty until proven innocent!!