ObjectiveTo investigate the clinical, radiographic characteristics and differential diagnosis of pulmonary Langerhans cell histiocytosis (PLCH) mimicking metastasis of cancer in radiography. MethodsClinical data of 2 patients with PLCH manifesting as metastatic cancer on HRCT and PET/CT were retrospectively analyzed. Patients reported as PLCH on WanFang Database, China Knowledge Resource Integrated Database and Pubmed were reviewed to screen misdiagnosis literature and further analyzed the clinical and radiographic characteristics. ResultsTwo cases both presented with cough and sputum. 18F-FDG PET/CT showed increased 18F-FDG up-take in both nodules in the lungs. One patient presented with multiple nodules, diffuse multiple cystic changes in lungs and osteoclasia in the right 4th rib on HRCT who was diagnosed by a video-assisted thoracoscopic biopsy of rib biopsy. The other patient presented with diffuse multiple nodules on HRCT who was diagnosed by a video-assisted thoracoscopic biopsy of lung biopsy. The pathological characteristics of both biopsy specimen demonstrated infiltration by Langerhans cells (LC) and eosinophils. The LC were positive for CD1a. Literature review found seven PLCH cases who were misdignosed as depression, eosinophilic pneumonia, interstitial lung disease involvement of autoimmune disorders and malignant tumor. ConclusionWhen clinician faced with a patient suspected as metastatic cancer by HRCT and PET/CT, it is reasonable to consider PLCH as a differential diagnosis and obtain the pathological information as soon as possible so that better prognosis can be achieved through early intervention.