Microwave-assisted frozen sectioning followed by disaccharide steeping improved pathological diagnosis during surgery for small adenocarcinoma of the lung

It is difficult to accurately define the size of lung lesions based on ground-glass opacities by computed tomography (CT), and diagnosis is usually made pathologically. Even the commonly use interpretations of prevalent frozen-section technique has some difficulties in the diagnosis detection of lesions appearing as ground-glass opacities, and in obtaining pathological information for a definitive diagnosis. In this study, we aimed to make a precise pathological diagnosis of lesions using the Noguchi classification, and accurately determine safe surgical margins by new fixation methods. We evaluated a microwave frozen section followed by sucrose steeping of small adenocarcinoma of the lung specimens intraoperatively. We examined 15 patients with early lung cancer undergoing video-assisted thoracic surgery with CT guidance followed by frozen-section examination. All resected lung specimens were fixed by an injection of 20% formalin solution that had been warmed by microwave irradiation to a minimum temperature of 65 deg C. Expanded and fully fixed specimens were cut into 2-3 mm sections, enabling easy detection of small lesions. Specimens were washed and steeped in 20% sucrose solution or trehalose solution for 30-60 seconds, to avoid crystallization of the water in the specimen, and then thin sliced sections were obtained using the usual cryostat method. All frozen specimens were compared with corresponding permanent sections regarding the diagnosis, the distance from the cut end of the specimen, fixation and staining ability, including immunohistochemical assessment. All frozen section specimens were consistent with the corresponding permanent sections from the point of view of morphology. There was no significant difference in the distance from the lesion to the surgical margin on the lung specimens. The method described was not only helpful for locating small adenocarcinoma that cannot be detected by palpation, but also provided easy evaluation of its morphology according to the Noguchi classification, as well as the surgical margin. (author)