[Neuroendocrine tumors of the lung]

The range of neuroendocrine tumors of the lung includes biologically benign and highly malignant tumors. Because of the different strategies of therapy, the pathologist is expected to provide a relevant classification. The classification in this article follows the categorisation of neuroendocrine tumors by Capella et al. [9]. Based upon this classification, the neuroendocrine tumors of the lung are divided in "benign or low-grade malignant" (I), "low-grade malignant" (II) and "high-grade malignant" (III) types. The pathohistological characterisation of these entities is based upon grade of atypia, nuclear crushing and molding, tumor cell size, the extension of tumor cell necrosis and finally the mitotic rate. Additionally, low-grade malignant tumors (II) can be separated from benign (I) and highly malignant (III) tumors by quantitation of MIB-1 immunoreactive tumor cells by automated image analysis systems. Finally, immunohistochemistry is helpful to prove the diagnosis in individual cases, particularly within the entity of large cell neuroendocrine carcinoma. The use of further "modern molecular" parameters or markers is currently without clearant diagnostic and prognostic aid.