A simple inflation method for frozen section diagnosis of minute precancerous lesions of the lung

BACKGROUND: Recently, the demand for intraoperative pathology consultation for small pulmonary nodules including ground-glass opacity (GGO) has been increasing. Evaluation of minute precancerous lesions of the lung by frozen section is very difficult for the pathologist as uninflated lung tissue usually shows severe atelectasis and frozen artifact. We tried to inflate lung tissue with the embedding medium used for frozen section and to determine the appropriate dilution ratio of the embedding medium for optimization of frozen section morphology. METHODS: The lung specimens were derived from 10 patients who underwent video-assisted thoracoscopic surgery (VATS) due to pneumothorax (four patients) and GGO (six patients) detected on high-resolution computed tomography (HRCT) at Seoul National University Bundang Hospital. The pneumothorax specimens were divided into six groups-uninflated, inflated with saline, and inflated with embedding medium (not diluted, 1:1, 2:1 and 2:3). The qualities of the frozen sections were compared with corresponding permanent paraffin sections. Lung specimens obtained from the six people with GGO detected on HRCT were submitted for intraoperative pathology consultation. Frozen sections were made after inflation with optimally diluted embedding medium determined by the above experiment with pneumothorax specimens, and the frozen section diagnoses (FSD) were compared with the final pathologic diagnoses of corresponding permanent paraffin sections. RESULTS: The frozen section quality of lung tissue was excellent after simple inflation with diluted embedding medium (2:3). Minute precancerous foci such as atypical adenomatous hyperplasia (AAH) and bronchioloalveolar carcinoma (BAC) could be readily identified in frozen sections using this method. Of the six patients with solitary GGO, four were diagnosed as BAC, nonmucinous type and two were as AAH on the frozen sections. Intraoperative FSD corresponded well with final diagnoses obtained with paraffin sections. CONCLUSIONS: An inflation procedure using diluted embedding medium can make lung tissue expand well during frozen section. Minute and even nonpalpable GGO lesions could be detected more easily by this technique in frozen sections, which would be helpful in determining how extensive a surgical procedure needs to be. Application of this procedure appears to improve the accuracy of FSD of minute precancerous pulmonary nodules.