Pocket of Fluid on Leg, Part Two

Pocket of Fluid on Leg, Part Two
(continued from Part 1)

Okay, so I left you all hanging on this weird case of Percy, the cat with the unusual cystic thingy on her front leg.   There’s more to the story, so here’s the update


Percy’s owner went to Blue Pearl Veterinary Partners for a second opinion and saw one of their surgeons, Dr. Andrew Kyles.  He examined Percy and was equally puzzled.  He basically agreed with my assessment and he recommended that Percy have a CT scan performed to evaluate the full extent of this cyst/swelling and see if there’s any solid tissue associated with it at all.  Depending on the CT findings, they would probably schedule the cat for surgery.  If it was just a cyst, they would try to remove it.  If it was a more solid type of mass, depending on how infiltrative it was, they would either try to biopsy and remove the mass, or in the worst case scenario, consider amputation of the leg.

Percy’s owner decided to pursue yet another opinion, and  I don’t blame her, especially when the word amputation  is mentioned.  She went to the Animal Medical Center.  They  discussed surgery, and she decided to have the surgeons at AMC do the procedure.  They opted not to go for a CT scan. The surgeons there felt it was very likely to be a cyst, and that they would try to remove it first and see what happens.

The surgeons at the AMC removed the cyst.  There was some solid tissue associated with the cyst, at the base.  They submitted a biopsy specimen.  The diagnosis:  “suspected synovial myxoma”.
Synovial myxomas are tumors of the synovium – the membrane that lines the joints.  They are mainly seen in middle-aged large-breed dogs.  The pathologist had never seen one in a cat.  She felt that this tumor was likely to grow back at the surgical site, but was not very likely to spread to other parts of the body.

AMC sent the sample to a different pathologist, for a second opinion on the biopsy.  A second pathologist agreed that a synovial myxoma is a plausible diagnosis.  It’s never been diagnosed in cats, though.   In May 2010, a review of 39 cases of canine synovial myxoma was published.   Because this hasn’t been described before in a cat, the AMC is probably going to try to publish this as a case report.  They are having special stains done on the biopsy specimen to try to characterize it further.  They are also contacting the author of that review article to help with the definitive identification of the tumor.

If synovial myxomas behave in cats the same way that they behave in dogs, then things might not be so bad for Percy.   In that review article, the average survival time in dogs was 2.5 years, even if the tumor wasn’t completely removed.  The tumor regrew at the incision site in a few dogs, but the tumor never spread to any other organs or directly resulted in any dog’s death.

After the special staining is done, we should have the truly final diagnosis.