Hot Quadrant Sign in a Lung Cancer Patient: A Rare Hepatic Pseudo-Lesion Unveiling Superior Vena Cava Obstruction

The hot quadrant sign is a rare yet clinically sensitive radiologic phenomenon characterized by focal enhancement of segment IV of the liver. It arises due to portosystemic venous shunting, most commonly due to superior vena cava obstruction (SVCO). This case report presents a 61-year-old male patient with a significant smoking history, weight loss, and symptoms suggestive of intrathoracic malignancy. Imaging confirmed a large right hilar and upper lobe pulmonary mass with extensive mediastinal invasion, complete SVCO, and a well-visualized hot quadrant sign on CT. The hepatic enhancement observed in segment IV was secondary to collateral venous flow via internal thoracic veins, a finding that could easily be mistaken for a hypervascular hepatic lesion. Early identification of this sign facilitated recognition of SVCO, supported a diagnosis of advanced lung adenocarcinoma, and prevented misinterpretation of liver imaging. This case emphasizes the clinical and educational importance of recognizing hepatic pseudo-lesions linked to systemic vascular abnormalities.