Cytologic, histologic and electron microscopic correlations in poorly differentiated primary lung carcinoma. A study of 43 cases.

For 43 poorly differentiated lung carcinomas we compared cytopathologic diagnoses made on specimens obtained prior to biopsy with histologic and electron microscopic diagnoses. Tissues were obtained by transbronchial biopsy, mediastinoscopy o pulmonary resection. Cytologies, tissues and electron micrographs were reviewed independently and blindly by five pathologists and one cytotechnologist. The cytologic, histologic and electron microscopic diagnoses agreed in 27 cases (62.7%), including adenocarcinoma (12), squamous carcinoma (five), oat cell carcinoma (six), mesothelioma (two) and adenosquamous carcinoma (two). In 14 cases the cytopathologic diagnoses had more accurately reflected the cell type ultimately diagnosed by electron microscopy than had the histologic diagnoses. Of ten poorly differentiated adenocarcinomas, eight had been interpreted as large-cell undifferentiated carcinomas, one as squamous carcinoma and one as poorly differentiated carcinoma histologically. Four poorly differentiated squamous carcinomas had been histologically diagnosed as giant cell, oat cell, undifferentiated carcinoma and adenocarcinoma. In these cases the previous cytologic diagnoses had been in agreement with the ultimate electron microscopic interpretation. The accuracy of cytodiagnoses may exceed that of histologic diagnoses in poorly differentiated lung cancer.