Mediastinal Castleman disease associated with pulmonary carcinoma, mimicking N2 stage lung cancer.

A 67-year-old man presented at our hospital with suspected right lung cancer with mediastinal and hilar lymphadenopathy. Although swollen lymph nodes had first been noted 8 years previously, only minimal enlargement had occurred over the intervening period. Video-assisted thoracoscopic biopsy of the pulmonary lesion and the mediastinal and hilar lymph nodes was performed. Final histopathological diagnosis was a poorly differentiated adenocarcinoma of the lung staged as T1NOMO and a coexistent localized hyaline-vascular type of Castleman disease. Right upper lobectomy was performed and postoperative histological findings suggested that this was likely to be curative. This is a rare case of coexistence of lung cancer and Castleman disease, illustrating the difficulties in distinguishing lymph node metastasis from other pulmonary diseases.