ABSTRACT
Lenvatinib, a multi-tyrosine kinase inhibitor, is used for the treatment of thyroid carcinoma. However, it can cause pneumonia and pulmonary cavitation leading to pneumothorax. The mechanism underlying the occurrence of cavitation and pneumothorax is not well understood. Coronavirus disease 2019 (COVID-19), which is an infectious condition characterized primarily by pneumonia, is sometimes accompanied by pulmonary cavitation. Patients with COVID-19 who present with pulmonary cavitation may have a poor prognosis. In the present case, a patient with papillary thyroid carcinoma presented with multiple pulmonary metastatic tumors that were treated with lenvatinib. After 9 weeks from treatment initiation, he experienced fever and presented with pulmonary consolidation and ground-glass opacity (GGO). Pneumonia improved after the withdrawal of lenvatinib. After 21 weeks from treatment initiation, he developed fever again and the clinical tests led to the diagnosis of COVID-19. Computed tomography (CT) showed new GGO in both sides of the lung. Therefore, the patient was diagnosed with moderate COVID-19. He was treated with dexamethasone plus remdesivir, and GGO due to COVID-19 disappeared. However, the previous pulmonary shadow associated with lenvatinib became a cavitary lesion. The initial CT findings of COVID-19 and pneumonia associated with lenvatinib are similar. Thus, both conditions must be considered for a differential diagnosis in patients presenting with GGO during lenvatinib treatment.