Complex sentence: Angiosarcoma arising in a region of chronic lymphedema, the Stewart-Treves syndrome, typically occurs in postmastectomy lymphedema of the arm and sporadically in a lymphedematous leg.
Split into simpler sentences: Angiosarcoma arising in a region of chronic lymphedema is referred to as Stewart-Treves syndrome. It typically occurs in postmastectomy lymphedema of the arm and sporadically in a lymphedematous leg.