Cat with a lump on her back

[Kate95]

     My cat, Hope, is about three years old.  I recently noticed a lump on her back.  The lump is located near the end of her spine, close to her tail.  The lump feels squishy, like it is filled with liquid.  It is about and inch in diameter and about half an inch tall. I tried to find something on Google, but could find nothing.
     I breed rabbits, and occasionally during the summer some kind of larvae gets under their skin and forms a lump, but since it is winter, I do not think this is likely.

[Aleda M Cheng, D.V.M., C.V.A]

The differential diagnosis for a free moving, fluctuant dermal mass includes: abscess, bot larvae (as your mentioned), sebaceous cyst filled with fluid or pus, basal cell tumor or other dermal tumor and more.  

For a definitive diagnosis I recommend that you have your veterinarian perform a fine needle aspirate and have a cytology performed; or your vet could remove the mass completely and send a biopsy to a pathologist for analysis.

[ireneo]

Is your cat an outdoor cat? It could be an abscess of some kind from an injury received outdoors. My one cat used to develop infections from flea bites (she was very sensitive to those). Perhaps the larva you're thinking of is cuterebra (nasty little things). But you'd be able to see a pore (breathing hole) in the lump. Do not attempt to squeeze it out. It needs to be removed by someone who knows how to do that without rupturing the larva.

Then again, it may be some kind of cyst. Seeing a vet would be wise to find out exactly what it is, what caused it and how to treat it.