In the present study, four independent cohorts comprising matched primary tumour (PT), malignant ascites, and peritoneal metastasis (PM) samples, along with paired pre‐treatment baseline and post‐chemo/immunotherapy (anti‐PD‐1/PD‐L1) progression ascites obtained from long‐term follow‐up, were generated and underwent single‐cell RNA sequencing (scRNA‐seq) (n = 30), multiplex immunofluorescence (mIF) (n = 30), and spatial transcriptomics (ST) (n = 3). The gene discussed is CD274; the disease is neoplasm.