Abstract
RATIONALE: Large cell neuroendocrine carcinoma (LCNEC) is a type of neuroendocrine carcinoma that is a rare malignant tumor that often coexists with adenocarcinoma in the same tissue. Adenocarcinoma cells may transform into LCNEC cells. The patient was found to have a liver mass 3 years after gastric adenocarcinoma surgery. Due to the absence of neuroendocrine cells in the liver, the patient's liver lesions may undergo neuroendocrine transformation after adenocarcinoma metastasis. PATIENT CONCERNS: The patient was found to have a liver mass 3 years after gastric adenocarcinoma surgery, and the preliminary clinical diagnosis was gastric cancer with liver metastasis. The patient has no discomfort symptoms, and the relevant physical examination shows no abnormalities. DIAGNOSES: Based on the patient's medical history, the preliminary clinical diagnosis is gastric cancer with liver metastasis (not excluding the possibility of primary LCNEC of the liver). INTERVENTIONS: The patient received surgical treatment and comprehensive treatment, including EP regimen chemotherapy and promotion of white blood cell growth. The patient received regular postoperative chemotherapy. OUTCOMES: The patient is currently undergoing regular outpatient follow-up. The patient was last followed up on September 18, 2024. LESSONS: This patient is a rare case of large liver cell neuroendocrine carcinoma after radical gastrectomy for gastric cancer, as the liver does not have neuroendocrine cells. The origin of liver neuroendocrine carcinoma is still unclear. Therefore, whether the patient was diagnosed with secondary liver metastasis of gastric cancer or concurrent liver in situ LCNEC is a difficult question. We hope to assist in solving relevant clinical problems through the special patient's situation.