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* From the Departments of Thoracic Surgery (Drs. Ikeda, Nomori, Mori, Kobayashi, Iwatani, and Yoshimoto) and Radiology (Dr. Kawanaka), Graduate School of Medicine, Kumamoto University, Kumamoto, Japan.
Correspondence to: Hiroaki Nomori, MD, PhD, Department of Thoracic Surgery, Graduate School of Medicine, Kumamoto University, Honjo 1–1-1, Kumamoto 860-8556, Japan; e-mail: hnomori{at}qk9.so-net.ne.jp
Abstract
Background: The developments in high-resolution CT scanning have increased the chance of detecting small bronchioloalveolar carcinoma (BAC) or atypical adenomatous hyperplasia (AAH) that appears as a ground-glass opacity (GGO). However, these lesions are not only difficult to localize during surgery, but they are also hard to make pathologic sections of because they are usually impalpable. Here, we report a method of making pathologic sections for impalpable GGO lesions.
Methods: Twenty-nine impalpable GGO lesions < 1 cm in size were marked by 0.4 to 0.5 mL of lipiodol under CT scan before surgery. The lesions were resected under C-arm fluoroscopy. The radiopaque areas marked by lipiodol within the formalin-fixed specimens were cut serially under conventional fluoroscopy for pathologic examinations.
Results: The mean (± SD) size of the lesions was 0.5 ± 0.2 cm (range, 0.2 to 1 cm), and the mean depth from the pleural surface was 1.6 ± 1.4 cm (range, 0.2 to 6 cm). The mean number of sections submitted for pathologic examinations was 2.3 ± 1.7 per lesion (range, 1 to 7 per lesion). While 11 of the 29 lesions (38%) were invisible even on the cut surface of the specimens, all were demonstrated in hematoxylin-eosin sections. The pathologic diagnosis was BAC in 17 lesions, AAH in 10 lesions, and organized pneumonia in 2 lesions. The use of lipiodol did not affect the pathologic findings.
Conclusions: The use of fluoroscopy to cut sections from resected specimens after preoperative marking with lipiodol was useful for making pathologic sections of impalpable GGOs < 1 cm in size.
Key Words: lung cancer • pathology lung cancer • thoracic surgery
The development of high-resolution CT scanning has allowed the frequent detection of small ground-glass opacity (GGO) lesions in the lung. Because a percutaneous or transbronchial biopsy of such lesions is often difficult, thoracoscopic surgical techniques have been used in diagnostic excisional biopsies as well as in therapeutic resections. Because small GGO lesions cannot usually be palpated or visualized during surgery, several marking techniques have been reported for localization during thoracoscopic surgery, such as those using a dye,123 colored collagen,4 barium,56 lipiodol,78 microcoil,9 and hook wire.1011 However, even if the lesions are successfully resected, it is still difficult to make pathologic sections of small GGO lesions because they usually cannot be palpated in the resected specimens. In addition, small bronchioloalveolar carcinoma (BAC) and atypical adenomatous hyperplasia (AAH) are sometimes hard to visualize on the cut surface of the resected specimens. This requires many pathologic sections to be made, which is time-consuming and expensive. To resolve these issues, we have performed preoperative marking with lipiodol for impalpable GGO lesions and have made pathologic sections under fluoroscopy, enabling the pathologic diagnosis to be made in all cases. Here, we report on the technique and the results of using it in detail.
Materials and Methods
Eligibility
The CT scan-guided lipiodol marking was approved by the ethics committee of Kumamoto University Hospital in April 2005. Written informed consent was obtained from all patients after they had discussed the risks and benefits of the procedure with the surgeons. Nodules that were potentially difficult to localize during surgery, or difficult to see or palpate on the cut surface of the resected specimens, such as GGO lesions or small nodules situated at a considerable depth from the pleural surface, were candidates for the procedure.
Patients
The nodules that were thought to be difficult to localize under thoracoscopy, such as GGO lesions, nodules situated at a considerable depth from the pleural surface, and nodules < 1 cm in size, were candidates for lipiodol marking. Between May 2005 and June 2006, preoperative lipiodol marking was performed under fluoroscopic CT scanning (AREX-T2310R1; Toshiba; Tokyo, Japan) on 60 nodules in 43 patients. Of these, 29 nodules in 18 patients were impalpable even in the specimens from patients who had undergone resection, who served as subjects in the present study (Table 1
). All of the nodules were incidentally detected on CT scan and had no solid component on multidirection CT scans (BRILLIANCE 64; Philips; Amsterdam, the Netherlands), which usually scanned the lesions with 0.5 to 1 mm thickness. All of the nodules were clearly visible, round GGOs < 1 cm in size, which were suspicious for BAC. Of the 29 lesions, 14 accompanied other resectable non-small cell lung cancers, 9 were part of multiple GGOs < 1 cm in size, and the remaining 6 were single GGOs. The mean (± SD) size of the lesions was 0.5 ± 0.2 cm (range, 0.2 to 1 cm), and their mean distance from the pleural surface was 1.6 ± 1.4 cm (range, 0.2 to 6 cm).
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Making the Cut Surface of the Resected Specimen
The resected specimens were inflated and fixed with a syringe of formalin using a thin needle. Intraoperative diagnoses of frozen specimens were not conducted. Formalin-fixed specimens were then viewed under fluoroscopy. The radiopaque area marked by lipiodol was cut serially at 5-mm intervals under fluoroscopy (Fig 2
). The sections including the radiopaque area were submitted for pathologic examinations (Fig 3
).
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All of the nodules could be marked on the CT scan images before surgery. Pneumothorax occurred in seven patients (39%), two of whom (11%) required drainage. No other complications were associated with the lipiodol marking. All of the 29 nodules could be successfully localized during surgery and completely resected. The surgical procedures used were wedge resection for 23 nodules and segmentectomy for 6 nodules.
All of the radiopaque nodules within the resected specimens could be seen distinctly on fluoroscopy even after formalin fixation. The mean number of sections submitted for pathologic examination was 2.3 ± 1.7 sections per lesion (range, 1 to 7 sections per lesion). While 11 of the 29 nodules (38%) could not be seen macroscopically on the cut surface of the sections, all could be seen microscopically and diagnosed pathologically (Table 2 ).
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Discussion
While the lipiodol-marking procedure is useful for localizing and resecting small pulmonary nodules,7 it is still difficult to make pathologic sections that include the pulmonary nodules from the resected specimens. This is made particularly difficult by the fact that GGOs < 1 cm in size are generally impalpable. In addition, AAH and BAC lesions < 1 cm in size remain hard to visualize on the cut surface of sections, even after formalin fixation. This requires many pathologic sections to be made, which is time-consuming and expensive. However, the present method enables pathologic sections to be made that include impalpable GGO lesions, which could not only reduce the number of pathologic sections required but also could allow a definitive pathologic diagnosis.
While many small GGO lesions have been found recently by high-resolution CT scans, the management of such lesions remains controversial.1213 Small GGO lesions are generally observed initially by CT scanning. Even if a nodule is subsequently discovered to be a BAC, this approach would not miss the chance of surgical cure because it would remain within the T1N0M0 stage during the follow-up period until it grew to 2 cm in size.141516 However, for GGOs with CT scan findings that are highly suspicious for BAC, such as those that are round and dense, it would be desirable to perform a surgical biopsy rather than a follow-up for the following reasons: (1) follow-up for at least several years would be necessary because of the slow growth of BAC lesions,17 which not only causes patients psychological stress but also entails the expense of follow-up CT scans; (2) while BAC lesions < 2 cm in size could be cured by limited lung resection, follow-up might result in tumors increasing in size and becoming more aggressive. This could miss the chance of a cure by limited resection and increase the need for lobectomy.1819 In addition, CT scan examinations before surgery for general lung cancers sometimes detect other small GGOs, and it is then necessary to understand whether these are double lung cancers or intrapulmonary metastases. Of the 29 GGO lesions in the present study, 17 were BAC lesions and 12 were nonmalignant lesions, including 10 AAH lesions. The 17 lesions with BAC could be cured by limited resection. Of the 12 nonmalignant lesions, 6 were resected with their associated lung cancers, which enabled accurate TNM staging. The remaining six nonmalignant lesions were resected along with their associated BAC or AAH lesion < 1 cm in size; in this latter scenario, pathologic diagnosis could be made and follow-up could be discontinued for a considerable time. We therefore think that a positive surgical biopsy finding is acceptable for GGO lesions with CT scan findings that are highly suspicious of BAC or is accompanied by other lung cancers, even if those were < 1 cm in size.
Several marking methods have been reported for the localization of small pulmonary nodules. These include the hook-wire technique,1011 microcoil,9 barium marking via bronchoscopy or percutaneous injection,56 percutaneous injections of dyes,123 colored collagen,4 and lipiodol.78 Because the general dye substances are water soluble, it is impossible to localize the dye-marked lesions after formalin fixation. The microcoil is under phase I study and has not been available in routine use.9 The barium is seen as a lesion in the hematoxylin-eosin-stained sections and also causes an inflammatory change of the lung tissue, which might make a pathologic diagnosis difficult. The hook-wire technique has been reported to cause massive air embolism,2021 which had led to its prohibition in Japan. The lipiodol that was used in the present study not only stays at an injected site even after formalin fixation due to its insolubility in water but also never affects the pathologic findings of the injected site. We therefore think that lipiodol could be one of the optimal markers for not only localizing GGO lesions but also making pathologic sections from resected specimens.
The only complication of lipiodol marking in the present study was pneumothorax in seven patients (39%), two of whom (11%) required drainage. This arose due to the insertion of the needle into the lung but not due to the lipiodol itself. Although we have never encountered air embolisms during percutaneous needle insertion into the lung, the risk of this complication has been reported to be 0.02 to 0.07%.20 In addition, lipiodol itself poses a potential risk of embolism because it is insoluble in water. We therefore take the following precautions: (1) prior to the injection of lipiodol, the syringe is withdrawn to confirm that blood has not flowed backward; (2) a minimum amount of lipiodol, up to 0.5 mL, is injected; and (3) lipiodol is injected under fluoroscopic CT scanning to confirm that it does not enter vessels during injection. While there have been no reports of embolism due to lipiodol itself, patients should be informed of the potential risk. Moreover, the procedure should be performed with an awareness of the risk of embolism due to air or lipiodol.
Footnotes
Abbreviations: AAH = atypical adenomatous hyperplasia; BAC = bronchioloalveolar carcinoma; GGO = ground-glass opacity
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
Received for publication August 2, 2006. Accepted for publication September 5, 2006.
References
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