Spontaneous regression of recurrent pulmonary large cell neuroendocrine carcinoma with alteration of PD‐L1 expression after surgical resection: A case report

Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive subtype of non‐small cell lung cancer with a poor prognosis. Spontaneous regression, that is, partial or complete disappearance of a malignancy without medical intervention, is extremely rare in LCNEC. Herein, we present a case of spontaneous complete regression in a 71‐year‐old male patient with recurrent LCNEC after surgical resection. The patient was diagnosed with stage IB LCNEC and underwent surgical resection. At 1‐year follow‐up, chest computed tomography revealed a recurrent lesion next to the stump site and enlargement of lymph nodes 4R and 7; recurrent LCNEC was confirmed. The patient declined chemoradiation therapy. One year after recurrence, the patient experienced severe multifocal necrotizing pneumonia and was treated with antibiotics, resulting in a gradual decrease in the size of the recurrent lesion. Five years after the initial diagnosis, positron emission tomography/computed tomography revealed no hypermetabolic lesions, indicating the spontaneous complete regression of LCNEC. Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive subtype of non‐small cell lung cancer with a poor prognosis. Spontaneous regression is extremely rare in LCNEC. We report a case of spontaneous complete regression after severe multifocal necrotizing pneumonia in a 71‐year‐old male patient with recurrent LCNEC after surgical resection.