Dear Doctor - A mysterious lump on the chin
My cat has a lump on her chin
Q My 17-year-old cat developed a lump in the underside of her neck in the past year, and it concerns me. About four years ago, she was diagnosed with an overactive thyroid, and I was instructed to give her 5 mg of methimazole twice a day.
She seemed to be losing weight, so the vet increased the dosage of the methimazole to 15 mg. After a few weeks, she developed a lump on her chin. The vet lowered her dosage to 10 mg, and after blood work, ultrasound and a biopsy, the lump was found to not be cancerous.
The vet drained the lump and she seems to be acting normally. The problem is that the cause has not been determined. It contains a tea-colored liquid and some blood from nearby blood vessels, and they feel it is dangerous to remove. Do you have any ideas what could be causing this condition?
A Dear Lorraine: If a tea-colored liquid is drained, then the mass must have a cystic component. The most common cystic structures in the neck originate from the thyroid gland, although other structures are also possible.
If an ultrasound has been performed, the origin of the mass can be assessed. A biopsy would confirm the origin. Since these tests have already been performed, you may wish to discuss with your veterinarian if there is additional information that might be helpful.
If your doctor believes the mass is too dangerous to remove, there are two options: Either periodically drain the cystic component when it becomes too large or seek a second opinion. I feel that your best option would be an appointment with a board-certified veterinary surgeon. You can locate a surgeon via the American College of Veterinary Surgery’s website, www.acvs.org. There is a search feature that identifies board-certified surgeons by state and town.
Michael Stone DVM, DACVIM
Clinical Assistant Professor
Cummings School of Veterinary Medicine at Tufts University