Upper Extremity Deep Vein Thrombosis Secondary to Gastric Cancer: A Case Report.

Upper extremity deep vein thrombosis (UEDVT) is uncommon and is frequently secondary to malignancy, central venous catheterization, or hypercoagulable states. Cancer‑associated thrombosis represents a major cause of morbidity and mortality in patients with malignancy. A 75‑year‑old Japanese woman presented with swelling of the left upper extremity accompanied by epigastric discomfort. Contrast‑enhanced computed tomography revealed thrombosis in the left subclavian vein and multiple metastatic lesions, including hepatic hilar lymph node and spinal metastases. Esophagogastroduodenoscopy demonstrated irregular mucosa with erosions from the gastric angle to the antrum, and pathological examination confirmed poorly to moderately differentiated adenocarcinoma with signet‑ring cell features. The patient was diagnosed with UEDVT secondary to gastric cancer. Anticoagulation therapy with unfractionated heparin improved swelling and pain, and the patient was transitioned to oral apixaban. Chemotherapy was subsequently initiated; however, the patient died nine months after diagnosis due to disease progression. This case highlights the importance of investigating occult malignancy in patients presenting with unexplained venous thromboembolism and initiating prompt anticoagulation therapy.