Lipoid pneumonia mimicking lung cancer: a retrospective case series and literature review

BACKGROUND: Lipoid pneumonia (LP) is a rare inflammatory lung disease caused by lipid accumulation in alveolar spaces. Its nonspecific clinical and radiological features often lead to misdiagnosis as lung cancer, resulting in potentially avoidable surgical interventions. METHODS: We conducted a retrospective case series of six patients who underwent surgical resection at our institution between 2019 and 2025 with a preoperative suspicion of lung cancer but were ultimately diagnosed with LP by postoperative histopathology. Clinical presentations, imaging features, tumor marker levels, and pathological findings were analyzed. RESULTS: All six patients had pulmonary nodules or masses highly suggestive of malignancy on chest CT, including ground-glass opacities, spiculated margins, and cystic changes. Two patients had elevated tumor markers (CEA (carcinoembryonic antigen) or NSE (neuron-specific enolase)). Final pathological examination revealed intra-alveolar lipid-laden macrophages, cholesterol clefts, and chronic granulomatous inflammation, consistent with LP. Most patients denied a specific history of lipid aspiration, though one case had a habit of applying intranasal cooling oil. CONCLUSIONS: LP can closely mimic lung cancer both radiologically and biochemically. A high index of suspicion is required in patients with atypical pulmonary lesions, even when tumor markers are elevated. Pathological examination remains the gold standard for diagnosis. Early recognition may help avoid potentially avoidable surgery.