Imprint Cytology for Detecting Metastasis of Lung Cancer in Mediastinal Lymph Nodes

Background Lymph node metastasis of lung cancer has been evaluated with histologic examination. We studied the usefulness of cytologic diagnosis for detecting metastasis of lung cancer in mediastinal nodes. Methods Five hundred twelve stations of mediastinal nodes in 157 patients with lung cancer were excised for staging of the disease through mediastinoscopy or thoracoscopy. Among them, 474 stations of mediastinal nodes in 151 patients were examined for metastasis both with imprint cytology and with hematoxylin-eosin histology independently. The final diagnostic decision was made by overall pathologic information, including cytology and histology. The diagnostic accuracies were compared between cytologic and histologic examinations. Results Cytologic examination identified 66 positive stations and 2 suspicious stations in 45 patients, whereas histologic examination identified 61 positive stations in 42 patients. The final pathologic diagnosis was 70 positive stations and 1 suspicious station in 45 patients. The sensitivity, accuracy, and negative predictive value of cytologic examination for node metastasis were 95.7%, 99.4%, and 99.3%, respectively, and those of histologic examination were 87.1%, 98.1%, and 97.7%, respectively. On a patient basis the sensitivity, accuracy, and negative predictive value of cytologic examination were 100%, 100%, and 100%, respectively, whereas those of histologic examination were 93.8%, 98.0%, and 97.2%, respectively. An additional 3 patients (2.0%) who had contralateral mediastinal node metastasis diagnosed only with cytology were identified with upstaged disease. Conclusions Imprint cytology for detecting metastasis of lung cancer in mediastinal nodes has high sensitivity and accuracy and is no less useful than histologic examination.