CASE PRESENTATION: A 35 y/o male with a history of prior tobacco use and occasional cocaine use presented with right-sided neck swelling and vein distention for three days. He denied trauma, fever, or chills. Vital signs were normal. Physical examination was remarkable for bulging right neck veins and swelling extending to the shoulder. Initial labs were significant for WBC 12.4 K/uL and D-dimer 4.66 ug/mL. CT angiogram of the head and neck showed acute thrombosis of the right internal jugular vein. He was started on systemic anticoagulation with enoxaparin. CT of the chest/abdomen/pelvis revealed a cavitary mass in the right lower lobe, enlarged nodes in right hilum and hypodense masses on the liver and right kidney, suggestive of widespread metastatic disease. Scrotal ultrasound was normal. IR-guided biopsy of the liver masses was positive for metastatic poorly differentiated adenocarcinoma with signet ring cell features. Immunostaining revealed that the tumor was positive for TTF-1, CK7, and CK20 suggesting primary lung origin. CDX-2, a highly specific marker for intestinal adenocarcinoma, was negative. MRI of the brain was negative for metastasis and endoscopy and colonoscopy did not reveal suspicious lesions. Patient was discharged on anticoagulation and started on carboplatin and paclitaxel for stage IV lung cancer.