Occult Metastatic Non-Small Cell Lung Cancer Presenting as Sepsis with Multi-Organ Dysfunction: A Diagnostic Challenge, a Case Report

Background: Sepsis is a critical illness arising from an infection, often accompanied by challenges in detection and treatment, particularly when the source of the infection is unknown or the patient’s condition progresses beyond expectations. Sometimes, clinically occult malignancies may either initiate or mimic sepsis, complicating diagnostic evaluation and management pathways.Case presentation: A 67-year-old White Hispanic woman with no previously documented chronic medical conditions presented with bilateral lower-extremity swelling, progressive weakness, and worsening fatigue. Upon admission, she exhibited septic shock physiology with multi-organ dysfunction, including acute kidney injury, hyponatremia, and deep vein thrombosis, raising concern for severe infection or malignancy-associated systemic inflammatory response syndrome. Chest imaging demonstrated bilateral pulmonary infiltrates, pleural effusions, and a dominant pulmonary mass. Additional imaging revealed multiple hepatic lesions and a solitary brain metastasis. Despite initiation of broad-spectrum antimicrobial therapy, microbiologic cultures remained unrevealing, and the patient’s clinical condition progressively deteriorated. Histopathologic evaluation of a liver biopsy ultimately confirmed metastatic pulmonary adenocarcinoma consistent with non-small cell lung cancer (NSCLC). Due to continued clinical decline despite aggressive supportive management, multidisciplinary discussions were held, and care was transitioned to comfort-focused measures. The patient passed away one week after hospitalization.Conclusion: This case highlights the challenges of maintaining an appropriate differential diagnosis in septic patients, especially when clinical findings are atypical or treatment responses are suboptimal. Optimizing outcomes and aligning management with patient goals requires early recognition of the underlying malignancy and timely involvement of palliative and specialty care teams.