Originally: †a tumour of striated muscle; a rhabdomyoma (obsolete). Later: any malignant tumour of muscle.
Now more common with the distinguishing prefixes leio- and rhabdo-, indicating origin from smooth or striated muscle, respectively.
Mid 19th century; earliest use found in Robley Dunglison (1798–1869), physician and medical writer. From myo- + sarcoma.