An assessment of the World Health Organization classification of the histologic typing of lung tumors applied to biopsy and resected material.

In a study of the World Health Organization classification of the histologic typing of lung tumors, sections from a total of 740 patients in the Medical Research Council Study of Cytotoxic Chemotherapy, 182 of whom also had positive preoperativebronchial biopsies and 231 involved lymph nodes in the resected specimens, and from 30 patients in the Medical Research Council Trial of Surgery and Radiotherapy in Small or Oat-celled Carcinoma of the Bronchus have been assessed. Of the 740 primary tumors from the Study of Cytotoxic Chemotherapy, 71% were placed in Type I, 12% in Type II, 9% in Type III, and 7% in Type IV. Only 2 primary tumors could not be typed. A blind comparison of the type of primary tumor and bronchial biopsy showed that the biopsy was a good indicator of the type of the primary tumor. A bind comparison of the primary tumor and involved lymph node also showed a close degree of agreement. However, when the type of the primary tumor was assessed in the presence of the involved node. Tumors were placed in Type IV far less frequently than when assessed blind. It is concluded that the World Health Organization classification is applicable to primary tumor, bronchial biopsy, and involved node, that the biopsy is a valuable indicator of the type of the primary tumor, and that the apparent type of the involved node should not be allowed to over-influence the pathologist in deciding on the type of the primary tumor when both are assessed together.