Case Report: Synchronous cutaneous and pineal metastases from gastric adenocarcinoma-inter-lesion biomarker heterogeneity and multi-line targeted therapy.

Gastric adenocarcinoma simultaneously metastasizing to the skin and pineal gland represents an extraordinarily rare clinical manifestation. Pineal metastases account for less than 1% of all adult intracranial tumors and seldom originate from gastrointestinal primary lesions, and this atypical metastatic combination frequently results in delayed diagnosis and complicated clinical decision-making. Distinct molecular profiles between primary and metastatic lesions create additional obstacles to personalized treatment, and relevant standardized management strategies for such rare cases have not been well established. We describe a 43-year-old woman with advanced gastric adenocarcinoma complicated by synchronous cutaneous and pineal metastases. Pathological evaluation confirmed the gastric origin of the cutaneous lesions, while the pineal lesion was presumptively classified​ as metastatic based on molecular concordance and clinical context. Guided by variable biomarker status across metastatic sites, sequential individualized targeted regimens were delivered, yielding sustained disease stabilization and satisfactory long-term survival. This case supplements clinical data on rare distant metastatic patterns of gastric cancer and highlights that repeated multi-site genetic testing is essential to formulate precise therapeutic plans for heterogeneous advanced gastrointestinal malignancies.