Intracranial metastasis following intrahepatic remission in primary hepatic small cell neuroendocrine carcinoma: a case report.

Background: Hepatogenic small cell neuroendocrine carcinoma (HP-SCNEC) is a highly aggressive rare malignancy, with central nervous system (CNS) metastasis being a major cause of treatment failure. This case report describes a patient with extensively metastatic HP-SCNEC, aiming to explore the clinical features of rapid brain metastasis following complete remission of intrahepatic lesions, as well as corresponding multidisciplinary treatment strategies. Method: A retrospective analysis of the diagnostic and therapeutic process in a 60-year-old female patient with HP-SCNEC. At initial presentation, the patient exhibited multiple intrahepatic metastases, abdominal lymph node involvement, and adrenal metastases. First-line therapy comprised the programmed death receptor-1 (PD-1) inhibitor sintilimab combined with etoposide and cisplatin. Following disease progression, whole-brain radiotherapy was administered for newly identified brain metastases, concurrently with systemic treatment adjustment to albumin-bound paclitaxel combined with anlotinib. Results: Following 6 cycles of immunotherapy combined with chemotherapy and 2 cycles of immunotherapy combined with anti-angiogenic therapy, the patient achieved radiographic complete remission of hepatic lesions. However, merely 16 days after achieving this remission, the patient presented with new-onset neurological symptoms, and subsequent imaging confirmed multiple new brain metastases. After undergoing whole-brain radiotherapy combined with an adjusted systemic treatment regimen, intracranial lesions were effectively controlled. The patient remained stable during subsequent maintenance therapy with Anlotinib. Conclusion: This case demonstrates that even when HP-SCNEC abdominal lesions achieve deep remission through intensified immunotherapy combined with chemotherapy, patients remain at extremely high risk for early brain metastases, highlighting the "intracranial sanctuary" effect caused by the blood-brain barrier. For such patients, prevention and monitoring of central nervous system metastases must be prioritized during initial treatment. Following brain metastasis, a multimodal comprehensive strategy centered on radiotherapy combined with intracranial active drugs should be adopted. This case provides important reference for the comprehensive management of this rare malignant tumor.