A 65-year-old man is admitted to the hospital with complaints of intermittent constipation and microcytic anemia. Barium enema reveals a non-obstructing "apple-core" lesion of the proximal sigmoid colon. Colonoscopy confirms the location of the mass and reveals no other synchronous lesions. Select the appropriate next step. (SELECT 1 STEP)
Left hemicolectomy Right hemicolectomy Subtotal colectomy Total colectomy