Sclerosing pneumocytoma with carcinoid tumorlets and neuroendocrine cell hyperplasia.

Sclerosing pneumocytoma is an uncommon pulmonary tumor which generally behaves benignly and occurs predominately in women. Rarely, it is associated with neuroendocrine proliferations such as hyperplasia, tumorlets and carcinoid tumors, which may be observed in relation to the tumor or in the distant lung parenchyma; the mechanism underlying this neuroendocrine differentiation is not clear. We present a case of a 33 year-old male with sclerosing pnemocytoma with coexistent neuroendocrine hyperplasia and combined carcinoid tumorlets.