Pulmonary Pathology of Early Phase COVID-19 Pneumonia in a Patient with a Benign Lung Lesion.

AIMS: An ongoing outbreak of 2019 novel coronavirus (SARS-CoV-2) diseases (COVID-19) has been spreading in multiple countries. One of the reasons for the rapid spread is that the virus can be transmitted from infected individuals without symptoms. Revealing the pathological features of early phase COVID-19 pneumonia is important to the understanding of its pathogenesis. The aim of this study was to explore pulmonary pathology of early phase COVID-19 pneumonia in a patient with a benign lung lesion. METHODS AND RESULTS: We analyzed the pathological changes of lung tissue from a 55-year-old female patient with early phase SARS-CoV-2 infection. In this case, right lower lobectomy was performed for a benign pulmonary nodule. Detailed clinical, laboratory and radiological data were also described. This case was confirmed to have preoperative SARS-CoV-2 infection by real-time RT-PCR and RNA in situ hybridization on surgically removed lung tissues. Histologically, COVID-19 pneumonia was characterized by exudative inflammation. The closer to the visceral pleura, the more severe the exudation of monocytes and lymphocytes. Perivascular inflammatory infiltration, intraalveolar multinucleated giant cells, pneumocyte hyperplasia and intracytoplasmic viral-like inclusion bodies were seen. However, fibrinous exudate and hyaline membrane formation, which were typical pulmonary features of SARS pneumonia, were not evident in this case. Immunohistochemical staining results showed that an abnormal accumulation of CD4+ helper T lymphocytes and CD163+ M2 macrophages in the lung tissue. CONCLUSION: The results highlighted the pulmonary pathological changes of early phase SARS-CoV-2 infection and suggested a role of immune dysfunction in the pathogenesis of COVID-19 pneumonia.