Large cell neuroendocrine carcinoma of the lung with a cystic appearance on computed tomography

Almost all reported cases of large cell neuroendocrine carcinoma (LCNEC) of the lung are solid-type tumors. We encountered a rare case of LCNEC displaying a cystic shape. An abnormal cystic shadow was revealed on chest computed tomography in a 71-year-old man who underwent total gastrectomy due to gastric cancer 5 years earlier. The cystic lesion enlarged from 7 mm to 16 mm over 7 months, so surgery was performed for definitive diagnosis and therapy. Microscopy revealed rosette patterns, a high mitotic rate and a large area of necrosis. Neuroendocrine differentiation was confirmed on immunohistochemical examinations using chromogranin, synaptophysin and NCAM (CD56). Given these findings, LCNEC was diagnosed. This is the first report of LCNEC with a cystic shape. This case challenges preconceptions regarding the radiographic appearance of LCNEC.