Longitudinal extension and distance from margin to proximal end of resected roentgenographically occult lung cancers

From April, 1982 to September, 1987, 83 patients with roentgenographically occult squamous cell carcinoma of the lung were discovered by mass screening and in our outpatient clinic. The bronchial trees were cut serially into 2-mm-thick blocks from the edge of the specimen to the ends of all the sub-subsegmental bronchi. The length of longitudinal extension was computed from the product of the thickness in mm of one serial block and number of consecutive blocks which included carcinoma from the most proximal to the most distal block. The distance from the margin of resection to the proximal end of extension was determined by the number of uninvolved blocks.In 72 of the 83 patients the carcinoma was confined within the bronchial wall and in 11 there was extrabronchial invasion. In 51 patients the tumor was located in a major bronchus and in 21 in a subsegmental or sub-subsegmental bronchus. Squamous cell carcinoma of the lung which is confined within a bronchial wall in any part of the bronchus without nodal involvement should be defined as early bronchogenic squamous cell carcinoma. There were no metastases to lymph nodes in the 62 patients in which the length of longitudinal extension was less than 20 mm. The margin of resection was positive for carcinoma in only one patient. The distance from the margin to the proximal end was 2 mm in 2 patients, ranged from 2 to 4 mm in 18 and was more than 4 mm in the remaining 62. To prevent the margin from being positive for carcinoma, it is advisable that the distance be at least 2 mm determined histologically. It is necessary to examine frozen sections and/or imprint specimens of the margin during operation. The desirable line of resection could be drawn at a distance of more than 1 ring of the intact mucosa from the proximal end of cancer extension as judged by bronchoscopy.