Pulmonary Langerhans cell histiocytosis with multiple cavitary nodules after lung cancer surgery.

Pulmonary Langerhans cell histiocytosis (PLCH) is a subtype of Langerhans cell histiocytosis, a rare neoplastic disease characterized by lung involvement. Here, we present a case involving a patient with multiple cavitary nodules who was diagnosed with PLCH during surveillance after lung cancer surgery. A 74-year-old woman underwent right upper lobe resection surgery for right upper lobe lung adenocarcinoma, pStage IIA, 5 years ago. The patient underwent surveillance without adjuvant chemotherapy. During the fifth year of follow-up, multiple nodules with cavitation were observed on computed tomography in both lung fields. Chemotherapy was considered to address the suspected recurrence of lung cancer; however, video-assisted thoracoscopic surgery was performed due to the need for biomarker testing. Pathological examination led to the diagnosis of PLCH. This case emphasizes the importance of a proactive histological diagnosis to determine the appropriate treatment strategy, even in situations where lung cancer recurrence is clinically suspected.