Abstract
Pulmonary sclerosing pneumocytoma (PSP) is pathologically classified as an adenoma and behaves in a benign manner. However, some cases of PSP displayed pathologically malignant behavior, such as lymph node metastasis and necrosis. A 64-year-old woman was referred to our hospital complaining of a cough and breathlessness. Histopathological analysis of the resected specimen by left pneumonectomy and lymph node dissection revealed a large PSP measuring 15 × 14 cm in size, with massive necrosis and vascular invasion. This case was the largest ever reported and suggested that clinico-histological presentation of PSP sometimes showed an aggressive phenotype like advanced lung cancer.