Gastric cardia cancer is a biologically heterogeneous malignancy arising at the gastroesophageal junction that is, the upper opening of the stomach rather than the heart. It develops along an inflammation-metaplasia-dysplasia-carcinoma sequence and remains clinically challenging because early lesions are often occult and advanced disease is shaped by a treatment-resistant tumor microenvironment. A clinically useful review therefore needs to distinguish gastric cardia cancer from non-cardia gastr