A surgeon was a specialist in invasive medicine.
Harry Sullivan was a Royal Navy surgeon. (TV: Planet of the Spiders)
Cassandra O'Brien had two surgeons with her in later life who had a responsibility to moisturise her. Their absence led to the skin drying out and tearing violently. (TV: The End of the World)
Dr Grace Holloway, a cardiologist, performed surgery on the Seventh Doctor. (TV: Doctor Who)