I am newly certified...a patient has a thyroidectomy which has a 90 day global surgical period...13 days later in the office(not O.R.) the same physician performs an incision and drainage of a seroma at the incision line. Help with modifier please? I know not 78 because he did not return to OR...I don't think 79 because it is related to surgery/same incision site...58 states staged/planned and this was not staged or planned. Carrier is MC. Can we bill for this incision/drainage of seroma with modifier (but which one?) Thanks.