Computed tomographic evaluation of mediastinal lymph node metastasis from primary lung cancer

In 63 cases of surgically resected primary lung cancers, the diagnosis of metastasis in mediastinal lymph nodes determined by thoracic CT scan was compared with postoperative histopathological evaluation. 1) Lymph node enlargement on CT scan was closely correlated with the actual size of the mediastinal lymph nodes. However, in the evaluation of metastasis, there were many false positive cases especially when the size of lymph nodes was 1.1 cm or more in maximum diameter on CT scan. It was considered that there was no metastasis when the lymph node was 1.0 cm or less in diameter, that there was a suspicion of metastasis in lymph nodes between 1.1 and 1.5 cm in diameter, and definite metastasis in lymph nodes 1.5 cm or more in diameter. 2) The overall accuracy was 78 %, with 71 % sensitivity and 79 % specificity. 3) Among the various histological types, the overall accuracy and specificity were slightly lower in cases of squamous cell carcinoma. 4) Concerning mediastinal lymph nodes, sensitivity was high for the No. 2 and 3, No. 4 and No. 6 lymph nodes; and low for No. 1, No. 5 and No. 7 lymph nodes. The specificity was high for No. 1, No. 4, No. 6 and No. 7 lymph nodes, but lower for the No. 2 and 3, and No. 5 lymph nodes, especially in cases of squamous cell carcinoma. Reference to the patient's history, the histological type and secondary changes induced by cancer can increase the accuracy of preoperative diagnosis by CT scan. CT scan was more exact for diagnosis of location, enlargement etc. of the mediastinal lymph nodes than ordinary chest X-ray films. However, further investigations are necessary for more precise evaluation of lymph node metastasis in future. (author)