Endocytoscopy for Confirmation of Surgical Margins of Peripheral Lung Cancer

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To the Editor:
For patients with lung carcinoma, complete resection of localized lesions is the only treatment option for long-term survival. Lobectomy has been the standard procedure to eradicate lung cancer cells; however, for patients with poor respiratory function, segmentectomy or partial resection is adopted instead. In these less-invasive procedures, it is important to assess precise surgical margins during operation. To date, most centers determine the final resection line according to the fresh-frozen sections.
Recently, ultra-high magnification bronchoscopy, or endocytoscopy (ECS), was introduced to enable contact microscopic observations through an optically magnifying objective lens and charge-coupled device.1 ECS enables real-time visualization of cellular structures of the superficial epithelium. In this report, our main purpose was to use postoperative ECS (BF-Y0005; Olympus, Tokyo, Japan) to assess for adequate surgical margins on resected peripheral lung cancer specimen.
A 70-year-old male patient had a history of left upper lobectomy. Ten years later, we recognized an abnormal shadow on right segment 6 (S6) on chest computed tomography (Fig. 1A); bronchoscopic biopsy revealed adenocarcinoma. However, review of the chest computed tomography revealed incomplete lobulation between S6 and S2, so we performed S6 segmentectomy, accompanied by S2 partial resection. Immediately after the operation, we used ECS to obtain microscopic images of the resected specimen. A drop of methylene blue (0.5%) was applied on the cut surface (Fig. 1B, left; Fig. 1C, left), after which “ultra-high” magnified images were recorded by ECS. The ECS had a magnification of ×400 and was projected on a 14-inch monitor.2 First, we attached the tip of the bronchoscope with ECS device to the surface of the tumor; cells and tissue structures similar to acinar adenocarcinoma were recorded (Fig. 1B, middle). Next, normal alveolar structures were viewed on the intact area beside the tumor (Fig. 1C, middle). Finally, we circumferentially moved the tip around the tumor margin and recorded images. From these ECS images, one could easily differentiate between normal alveolar structures and cancerous lesions; therefore, we opted not to send the specimen for fresh-frozen section.
Final histopathologic examination of thin-slice specimens with hematoxylin and eosin staining revealed invasive adenocarcinoma, acinar predominant. The ECS images and histopathologic findings were compared; cancer cells and tissues (Fig. 1B, right), normal alveolar tissues (Fig. 1C, right), and tumor margins were identified. The similarities between the ECS images and histopathologic findings of the corresponding sites were identified. These results led us to believe that ECS has the potential to acquire stable images that are similar to that of conventional hematoxylin and eosin staining and replace intraoperative frozen section examination.
So far, the reported clinical applications of ECS for bronchial mucosa were in vivo histologic diagnoses.3,4 We previously applied ECS to the evaluation of the margin and structures of bronchial squamous cell carcinoma in the resected bronchus.2 This application verified the usefulness of ECS for ex vivo histologic diagnosis of the bronchial mucosa. To the best of our knowledge, this is the first report on the use of ECS on resected peripheral lung tissue. ECS enabled ex vivo diagnosis of lung cancer and immediate assessment of surgical margins, which were later confirmed on histopathology. This technique may open a new field of rapid intraoperative diagnosis and shorten operative time. However, further studies are needed to validate the diagnostic yield of ECS compared with that of standard histopathology.

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