Signet Ring Cell Carcinoma of the Stomach with Chylous Pleural Effusion: Laterality Shift and Fluid Composition Change

This case is unique because it demonstrates a rare progression from bilateral to unilateral pleural effusion, accompanied by a transition in pleural fluid characteristics, which has not been previously reported. The observations suggest dynamic changes in lymphatic obstruction and tumor infiltration. Early molecular profiling, which includes CLDN18.2 testing, may provide new opportunities for targeted therapy in aggressive gastric cancer cases.