Expert: Jessica - 6/27/2010

Question
My cat has a small lump on the middle of his back. I didn't think anything of it at first until I noticed today that when I ran my hand along his back there was a wet spot. So I pulled the hair back and found a hole about the size of pencil lead and it had a kind of clear but a kind of milky fluid coming out when he would breath in. I squeezed it a little and more fluid came out but it didn't seem to hurt him. There seems to be like a little black speck in the center of the hole. The area around the hole is red but the hole its self look pink. He doesn't act any different either. He still runs around and plays with the other cat.What could this be and should I take him to a vet.

Answer
Hi Jessica,

I'm not really certain what's going on with your cat.  One of the things that comes to mind is a warble.  This is a lump that's created by the parasitic larva of a bot fly.  This happens almost entirely to cats who go outdoors.  Their fur comes in contact with a bot fly egg, which hatches.  The larva makes its way to the skin and cuts into it, burrowing under, where it will grow for about 6 weeks.  It produces a lump that becomes quite large toward the end of its growth.  The worm leaves a hole in the cat's skin so that it will be able to breathe, and also so that it will be able to exit once it's finished growing.  The larva does appear as a black dot in the hole as it gets bigger.

Usually, the larva will back itself out of the hole once it's finished maturing, and that's the end of the story.  Unfortunately, the hole that's left is quite large and is prone to infection.  Also, some larvae grow so large that they can't get out of the hole.  When they die, they leak toxins into the bloodstream that can kill the cat.  So it's important to have a vet remove bot fly larva carefully.  Some people try to remove them themselves or try to kill them by flushing them with alcohol or suffocating them with Vaseline.  Remember - if the larva dies in the hole, it will leak toxins that can kill the cat, so it's safest to have the vet take care of it.

There are some growths on cats that can leak fluid, especially sebaceous cysts, and these are most commonly found on the back.  They're similar in nature to giant zits!  They're full of an oily substance produced by glands under the skin, and the cysts are harmless.  They may be caused by an ingrown hair, a splinter or a scratch, or some cats are just prone to them for unknown reasons.  The cysts are slow growing and do tend to rupture on their own after a while.  However, rather than a milky fluid, they usually release a waxy material.

Any lumps definitely should be investigated by a vet, because they all have the potential to be serious.  Besides cysts and warbles, abscesses and cancer are other possibilities.  I would get your kitty to the vet on Monday.

Best wishes!

Jessica