[Recent advances in pathology and biology of small cell lung cancer].

Small cell lung cancer (SCLC) is histologically simple and looks undifferentiated, but possesses cytoplasmic dense-cored granules resembling neuroendocrine granules, and frequently produces amine and peptide hormones, occasionally presenting related symptoms. Among these bioactive substances, gastrin releasing peptide (GRP) is most important, which is known as autocrine growth factor and one of the useful monitoring markers for SCLC together with neuron-specific enolase. Aromatic L-amino acid decarboxylase is another important enzyme in SCLC. Abnormality of myc family oncogenes is occasionally noted in SCLC, which appears related to proliferative activity of the tumor rather than development. Deletion of chromosomes 3p, 13q and 17p is noted in almost every SCLC, where antioncogene is suspected to be present, and inactivation of antioncogene may play an important role in development of SCLC. Nucleolar size is the important parameter for proliferative potential of SCLC. The larger the nucleoli, the faster is the growth of SCLC. Phenotypes of SCLC in vitro may be altered by change of microenvironment, although it may be due to the selective growth of a certain clone. SCLC and nervous tissue specific membrane antigen is named cluster 1 SCLC antigen, the monoclonal antibody to which will be utilized for immunohistological diagnosis, imaging and treatment of SCLC. Accumulation of basic knowledge is now leading to reconsideration of histological subtyping of SCLC.