BackgroundThe primary pulmonary lymphoma (PPL), with a low incidence, was highly misdiagnosed in clinic. The present study analyzes the clinical features, laboratory and imaging data, pathologic characteristics, and summarizes misdiagnosis reasons of PPL cases, aims to provide a better understanding and increase the accuracy of early diagnosis and minimize the misdiagnosis of PPL.MethodsThe clinical data of 19 cases were collected from the first affiliated hospital of Wenzhou medical university (PRC) from April 2010 to May 2016. All cases were confirmed by pathology. The process of misdiagnosis was described. This study retrospectively analyzed the incidence, clinical presentation, laboratory examination, Chest CT scan and diagnosis of the cases.ResultsThe symptoms of the 19 cases were dyspnea, fever, hemoptysis, chest pain or physical findings without obvious symptoms. Five patients were pneumonia-like, nine patients had lung single nodule or mass and four patients got pleural effusion, which were reported by computed tomography (HRCT) scan. There were 2 cases of Hodgkin lymphoma (HL), and 17 cases of non-Hodgkin lymphoma (NHL). In NHL cases, 12 cases were confirmed mucosa associated lymphoid tissue B lymphoma type, 3 cases were confirmed diffuse large B-cell lymphoma, angioimmunoblastic T-cell lymphoma and ALK positive anaplastic large cell lymphoma were one case separately. Clinical and imaging manifestation of PPL is untypical, but there are still some hints: 1) Fuzzy shadow at the edge of lung mass with air bronchogram; 2) Lung mass shadow stable for a long time; 3) Pneumonia-like changing without infections clinical and lab manifestation. Thirteen patients (68.4%) were misdiagnosed as pneumonia, lung cancer and tuberculosis initially. The term between initial diagnosis and final diagnosis lasted for half a month up to 2 years, with median time of 6 months. Two cases were misdiagnosed as tuberculosis. One case was misdiagnosed as small cell lung cancer.ConclusionClinical and imaging manifestation of PPL is untypical. Biopsies should be taken actively if the imaging findings don’t match the symptoms or the anti-infection treatments to “lung infection” don’t work. Accurate diagnosis requires adequate tissue sampling with appropriate ancillary pathologic studies. If clinical manifestation and the diagnosis don’t match, repeated biopsy should be ordered.

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