Up until Tuesday Sept 4, the cyst remained about the same size.
Slight pressure on it resulted in a powerful squirt of some 1cc of serous fluid, with the size of the cyst reducing. There was a similar occurrence on Wednesday. The current size of the cyst is much reduced, although there is a residual palpable lump (much less in size).
History recalls that the skin of the paws for the foot corresponding to the location of the cyst was slightly raw, reddened and irritable. Also he has been walking in areas where foxtail abounds.
So the most likely diagnosis is foxtail.
The questions are:
A. What is the most favorable management?
1. Do nothing and wait (in the meantime cytologic examination)
2. Widen the current aperture that the needle made and wait in case the suspected foxtail drains (perhaps unlikely)
3. Incision and removal of the foxtail, if located. It is most probably embedded in the soft tissues, although it could be in the cavity.
4. Incision and curettage of the area, checking for location of the foxtail.
5. Complete surgical removal of the affected area.
B. Assuming A 2&3 (and perhaps 1, although sedation and a nerve block might suffice) requires a general anesthesia.
Q: What is the risk of death from the anesthesia (best guess)
Less than 1%, 1-4%, 5-9%, >9%? - given Luther is a healthy 11 yr old.