Đặc điểm lâm sàng, hình ảnh nội soi và mô bệnh học của bệnh nhân ung thư dạ dày dưới 50 tuổi tại Bệnh viện Ung Bướu Đà Nẵng = Clinicals, endoscopic images and histology of stomach cancer patients under 50 years old at Da Nang Cancer Hospital