We reported a case report of mass-like cecum and ascending colon carcinoma featuring exophytic cavity growth. The external lump size was about 84 mm × 72 mm that violated right-side illiopsoas and psoas major muscles. Preoperative CT diagnosis was performed to confirm a retroperitoneal cancer involving right hemicolon, psoas major and casiliopsoas muscles. Mesenchymoma was the paramount consideration. Besides, right hemicolon excision and involved psoas major excision were performed during operation. The postoperation pathology showed that colon cancer has involved iliopsoas and psoas major muscles. Above all, the patients recovered well after operation.