[Pathological variability and cancer treatment in lung cancer]

It is well known that the biological behavior of lung cancer varies according to histological type and growth pattern. Therefore, more precise analysis of various morphologic features affecting prognosis are needed based on tumor histology. Lung cancer is mainly classified into 4 major histological types; squamous cell carcinoma, small cell carcinoma, adenocarcinoma and large cell carcinoma. Recently lung cancer has been subclassified into small cell carcinoma and non-small cell carcinoma on the basis of responsiveness to chemotherapy and radiation therapy. In small cell carcinoma, combination of chemotherapy and radiation therapy is the main modality for treatment, and the most important prognostic factor is LD and ED stage classification. Even so, a new histological classification is proposed according to the responsiveness to chemotherapy and radiation therapy. On the other hand, surgical therapy is the first choice for the treatment of non-small cell lung cancer and the most important prognostic factor is TNM and related stage classification. In squamous cell carcinoma, moreover, extended resection is sometimes tried because of its local invasiveness. Early lung cancer of hilar type is mostly squamous cell carcinoma and highly curative by resection. The biological behavior of adenocarcinoma is the most variable among lung cancers. In the histopathological study of surgically resected cases, moreover, histological differentiation, nuclear atypia of tumor cells, mitotic frequency, grades of scarring associated with a tumor, and degrees of infiltration of T-zone histiocytes is closely related to prognosis. Scoring of these factors may help a clinician to reach a decision on the necessity and type of postoperative adjuvant chemotherapy, particularly in cases of Stage I adenocarcinoma. Most cases of large cell carcinoma including giant cell carcinoma ultrastructurally reveal features of differentiation toward adenocarcinoma and/or squamous cell carcinoma. Giant cell carcinoma shows the most unfavorable prognosis because of its rapid growth. However, among operable cases of giant cell carcinoma, some long-term survivors do exist. Evaluating these forms of biological behavior according to tumor histology at the time of treatment, it is easier to decide whether or not adjuvant therapy is necessary.