Before writing off the charge, I'd confirm whether the correct CPT code was used.
This CPT code indicates that a tumor is excised from the deep soft tissue, below the fascial plane or within the muscle. It would be done under anesthesia and allows an assistant surgeon.
Does the documentation support the excision of an intramuscular tumor? Or is there a more accurate excision CPT code that would be used?
To answer your question about office-based procedures, though, CMS classifies 21932 as a non-office-based surgical procedure.
(That distinction means that when performed in an ASC, it will be paid at OPPS rates. When a surgical procedure commonly performed in provider offices gets done in an ASC, the payment is capped at the MPFS rates. That payment provision theoretically keeps procedures from being shifted from the office to the ASC. Status indicator G2 means a procedure isn't commonly done in the office so that the ASC will be reimbursed at OPPS rates. You could look at the G2 indicator for a general idea of what CMS thinks isn't commonly done in the office - just remember the purpose of the indicator is for ASC reimbursement. It shouldn't be taken as an absolute list to be followed by a physician's office.)
Your best bet is to see whether the documentation actually supports CPT 21932.