Mucinous gastric adenocarcinoma (MGC) is a distinct but under-researched subtype of gastric cancer, accounting for approximately 2.2% to 6.8% of all cases. It is characterized by the presence of ≥50% extracellular mucin within the tumor tissue. Although recognized as an independent subtype by international classification standards, significant controversies persist regarding the definition criteria, clinical prognosis, and treatment strategies of MGC. This article systematically reviews the epidemiological features, histological evolution, molecular mechanisms, and imaging characteristics of MGC, with a particular focus on the key issues related to definitional discrepancies, prognostic contradictions, and therapeutic challenges. Addressing these issues may provide references for optimizing clinical diagnosis and treatment, promote the development of individualized therapeutic strategies for MGC, and offer theoretical support for reducing global disparities in gastric cancer management.