Immunotherapy alone or chemo-immunotherapy has recently been recommended for treating advanced lung carcinoma in patients without driver mutations. However, the efficacy of immunotherapy and molecular mechanism in large-cell lung cancer (LCLC) remains unclear. Here, we reported a rare case of multiple fulminant postoperative body and mouth metastases in LCLC treating with combination immunotherapy. Initially, the patient was diagnosed as early stage LCLC and underwent a radical resection of the right lower lobe. Just one month later, multiple fulminant body and mouth lesions appeared in the right upper arm, right elbow, right waist, and tongue root. Meanwhile, serum neuron specific enolase (NSE) concentration dramatically increased from 12.12 to 30.14 ng/ml. Immumohistochemistry findings demonstrated moderate PD-L1 expressions with tumor proportion score (TPS), while next-generation sequencing indicated moderate tumor mutational burden (TMB) levels and gene mutations in PBRM1 L1230P and TP53 L194R of both foci. Besides, loss of heterozygosity (LOH) at human leukocyte antigen (HLA) class I (HLA-A*02:03, HLA-B*55:02 and HLA-C*12:03) were detected in the right upper arm metastasis, which may facilitate malignant postoperative metastases in this case. Notably, this patient received combination therapy with anti-PD-1 antibody sintilimab plus anlotinib, and achieved a partial response for at least 12 months. Using an integrated computational method, the mutant peptide TEIPENDIPL derived from PBRM1 L1230P was predicted to be a specific neoantigen and could still be presented by HLA-B*40:01. This case suggests that immunotherapy plus antiangiogenic drug may provide an alternative therapeutic option for advanced LCLC patients without common gene mutations.