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Thoracic Imaging |
1 From the Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021. From the 1998 RSNA scientific assembly. Received November 17, 1998; revision requested December 22; revision received January 22, 1999; accepted February 15. Address reprint requests to M.S.G. (e-mail: ginsberm@mskcc.org).
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Abstract |
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 TOP Abstract IntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS: Pathology reports from VATS performed between January 1995 and July 1997 were searched for data on gross specimens revealing pulmonary nodules 3 cm or smaller. Findings were correlated with clinical and histologic data.
RESULTS: In 254 patients with one nodule resected at VATS, the nodules were malignant in 108 patients with and in 32 patients without known cancer (P < .03). Among 172 patients with multiple nodules resected, at least one nodule was malignant in 85 patients with and in 20 patients without known cancer (P > .05). Nodules larger than 1 cm were more likely to be malignant than were smaller nodules (P < .002). In patients with known malignancy, nodules smaller than 0.5 cm were more likely to be benign, whereas nodules larger than 0.5 cm but smaller than 1 cm were more likely to be malignant (P < .001).
CONCLUSION: A single pulmonary nodule resected at VATS was more likely to be malignant in patients with known cancer. Nodules larger than 1 cm but smaller than 3 cm resected at VATS were more likely to be malignant. Nodules smaller than 0.5 cm were more likely to be benign.
Index terms: Lung, diseases, 60.3119 • Lung neoplasms, 60.31, 60.32, 60.33 • Lung, nodule, 60.281 • Lung, surgery, 60.1299 • Thoracoscopy, 60.1299
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Introduction |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Video-assisted thoracoscopic surgery (VATS) is a technique that has recently become available for evaluating pulmonary nodules in which the etiology is not apparent from radiologic studies. It is a minimally invasive procedure that has a reported sensitivity and specificity of 100% and is associated with virtually no mortality and minimal morbidity (5–7). However, VATS involves greater morbidity and is more costly than other less invasive procedures such as percutaneous needle biopsy and bronchoscopy. We undertook this study to evaluate the probability of malignancy in single or multiple pulmonary nodules resected at VATS in patients with and in those without a known malignancy and to stratify the results according to the histopathologic type of the primary tumor.
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Patients were stratified by presence or absence of known malignancy at the time of VATS, as well as according to the number of pulmonary nodules (single vs multiple [ie, more than one]) resected at VATS. Note that in some patients, only one of several pulmonary nodules present was resected at VATS. Patients who had multiple pulmonary nodules resected were also categorized according to whether all resected pulmonary nodules were benign or at least one was malignant.
The benign nodule category included granuloma, scar, inflammation, hamartoma, lymph node, and tumorlet (see Discussion section). The malignant category consisted of non–small cell and small cell (including carcinoid) lung cancer and pulmonary metastasis (Table 1). The nodules were further categorized by size as follows: less than or equal to 0.5 cm, larger than 0.5 cm but less than or equal to 1 cm, or larger than 1 cm but less than or equal to 3 cm.
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2 statistical analysis by using one degree of freedom. P values of less than .05 were considered to be significant. |
RESULTS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Of the 114 single resected nodules that were benign at histopathologic examination, 20 were hamartomas, 15 were intrapulmonary lymph nodes, and 79 represented granulomas, fibrosis, scar, inflammation, or tumorlets (see Discussion section).
Multiple Pulmonary Nodules Resected at VATS
One hundred seventy-two (40%) of the 426 patients had multiple pulmonary nodules resected at VATS. Of these 172 patients, 105 (61%) had at least one malignant pulmonary nodule resected. In 85 (64%) of the 133 patients with a known malignancy, at least one of the resected pulmonary nodules was malignant. In 48 (36%) of the 133 patients with a known malignancy and multiple pulmonary nodules resected at VATS, all of the resected nodules were benign. Thirty-nine of the patients in whom multiple pulmonary nodules were resected at VATS had no known malignancy; in 20 (51%) of these patients, at least one nodule was malignant (Fig 3). The prevalences of multiple malignant nodules in patients with a known malignancy and in those without a known malignancy were not significantly different (P > .05).
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The nodules 1 cm or smaller were more likely to be benign in patients with no known malignancy. Sixty-three (69%) of 91 pulmonary nodules that were 1 cm or smaller and resected at VATS in patients with no known malignancy were benign compared with 206 (49%) of 424 nodules resected at VATS in patients with a known malignancy (P < .001). In patients with no known malignancy, a small nodule was more likely to be benign. Twenty-eight (68%) of 41 pulmonary nodules 0.5 cm or smaller and 35 (70%) of 50 pulmonary nodules larger than 0.5 cm but less than or equal to 1 cm were benign. In patients with a known malignancy, pulmonary nodules 0.5 cm or smaller were more likely to be benign, which was the case in 160 (58%) of 275 nodules, whereas pulmonary nodules larger than 0.5 cm but less than or equal to 1 cm were more likely to be malignant, which was the case in 103 (69%) of 149 pulmonary nodules (P < .001) (Table 4).
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The term "tumorlets" was encountered in several of the pathology reports of the patients in our study. A pulmonary tumorlet is a minute epithelial lesion that is encountered as an incidental finding during microscopic examination of the lung, particularly in lung scarred by bronchiectasis or other chronic inflammatory processes (11). Tumorlets are considered to be tiny peripheral carcinoid lesions that differ from the larger lesions that are identified as carcinoid tumors mainly in size (12). Tumorlets are usually smaller than 5 mm and multiple, and there are two types: carcinoid and chemodectoma (13,14). Both types are composed of small uniform cells that are cytologically benign, and both tend to form compact aggregates or nests. However, the carcinoid type is intimately related to the epithelial lining of the bronchoalveolar tree and often projects into the airspace, whereas the chemodectoma type is arrayed around small pulmonary veins, with similar cells extending in a spider web pattern into the adjacent interalveolar septa. In addition, tumorlets of the carcinoid type contain neurosecretory granules, whereas tumorlets of the chemodectoma type lack such granules (15). It must be emphasized that tumorlets are incidentally discovered, benign lesions—contrary to the intuitive meaning of the term, which would suggest that they are "small malignant tumors," such as metastases in patients with cancer.
In addition to the usual array of benign lung nodules and pulmonary metastases, two other specific types of pulmonary nodules may manifest in patients with a known malignancy: sarcoid-like reactions and sterilized metastases. Sarcoid-like reaction denotes the occurrence of noncaseating pulmonary granulomas in patients with malignancy who have no symptoms or other signs of systemic sarcoidosis. The noncaseating granulomas of sarcoid-like reactions are morphologically identical to the granulomas of sarcoidosis, and there are no distinct radiologic findings that distinguish these granulomas from those of sarcoidosis (16). The term "sterilized metastasis" has been used to define a pulmonary nodule that persists after treatment with either no change in size or appearance or an initial decrease in size followed by no change (17). These persistent nodules consist of necrotic and/or fibrotic tissue without viable tumor. It is interesting that we did not encounter sarcoid-like reactions or sterilized metastases in this relatively large population of patients with cancer.
The nodule was malignant in 140 (55%) of 254 patients with a single pulmonary nodule resected at VATS; these findings are similar to the results of the study by Munden et al (10). In patients with multiple nodules resected at VATS, we found that a similar proportion of patients (61%) had at least one malignant nodule. As has been reported by others (4), we found that the presence of a known malignancy increases the likelihood that a small pulmonary nodule will be malignant at VATS. In patients with a known malignancy and a single resected pulmonary nodule, the nodule was malignant in 59% of patients versus in 44% of patients with no known malignancy (P < .03). In patients with multiple resected nodules and a known malignancy at the time of VATS, the prevalence of malignancy was 64% compared with 51% in patients with no known malignancy (P > .05). These results are in accordance with those of other authors (18) who have suggested that both single and multiple pulmonary nodules have a high likelihood of being malignant and that metastatic disease is more common among multiple nodules. In another study (19), a prevalence of malignancy as high as 84% in pulmonary nodules in patients with a known extrathoracic cancer has been suggested; however, these results are based on 237 pulmonary nodules in 84 patients.
Pulmonary nodules larger than 1 cm but 3 cm or smaller were more likely to be malignant than were those smaller than 1 cm (P < .002). This was true both of patients with a known malignancy and those without a known malignancy, although the likelihood of malignancy in pulmonary nodules was higher in those with a known malignancy. In patients with no known malignancy, a pulmonary nodule 1 cm or smaller was more likely to be benign. In patients with a known malignancy, the pulmonary nodules 0.5 cm or smaller also were more likely to be benign, whereas the pulmonary nodules that were larger than 0.5 cm but less than or equal to 1 cm were more likely to be malignant (P < .001). Pulmonary masses larger than 3 cm also are known to have a high probability of being malignant (4).
We obtained our data on the pulmonary nodules in this study from pathology reports of patients who underwent VATS. We did not examine CT scans obtained before VATS was performed to assess individual pulmonary nodules for several reasons. It would not have been possible to retrospectively correlate specific individual nodules resected at VATS with findings at CT, particularly when multiple nodules were present. Also, not all nodules detected at thoracotomy are detected at VATS or at CT (6). This would have further confounded our attempts to evaluate specific nodules at CT. However, because we studied only the pulmonary nodules that were visible at gross pathologic examination, it is likely that such nodules would have been visible on chest CT scans, unless they were not imaged for technical reasons or not detected owing to a complex surrounding background. Finally, many of the CT scans would not have been available for retrospective review, because a large number of our patients take the scans obtained outside our institution back to their local hospital. The lack of radiologic correlation limits the application of our results to standard radiologic interpretation; nevertheless, our results can be applied to specific situations in which one or more pulmonary nodules are to be resected at VATS.
The aim of our study was to establish the prevalences of benign and malignant pulmonary nodules resected at VATS in large numbers of patients with and without known cancer, as occurred in our large clinical oncologic practice. We realize that the patient population at our specialized cancer center is skewed. Also, the total number of patients with pulmonary nodules seen at our institution during the study period was much higher than the number of patients in the final study group; most of the patients did not undergo VATS for resection of the nodules for various reasons, including known or clinical suspicion of metastatic disease elsewhere to the extent that proof of lung metastases would not have altered treatment.
Some patients with small pulmonary nodules probably underwent other diagnostic procedures such as needle biopsy in lieu of VATS; including them would have biased the patient sample. Moreover, the nodules evaluated in this study represented only a sample of all the nodules present in the patients in the study group, because only some of the nodules present were resected at VATS. Our designation of "single nodule" often represented the one nodule of most clinical concern and/or the one nodule most accessible for resection at VATS among several nodules. Our institution has a large population of patients with cancer, and, as such, there was some bias in the selection of our patient population.
Even with these types of differences in patient selection, our results are consonant with those of Patz et al (20), who evaluated patients with multiple pulmonary nodules and a single known malignancy. In that study, a higher prevalence of pulmonary metastatic disease was demonstrated in patients who had a diagnosis of melanoma, breast cancer, or colon cancer and multiple pulmonary nodules at chest radiography or CT and were evaluated by using subsequent percutaneous needle biopsy.
When we analyzed the pathology reports of patients with lung carcinoma, it was sometimes difficult to determine whether a resected pulmonary nodule represented another malignant lung tumor or a metastasis from a previous lung carcinoma. Sometimes, such a distinction could not be made by the pathologist; this reflects the problems that pathologists encounter when attempting to distinguish synchronous or metachronous lung cancers from metastases of lung cancer. When the histopathologic features of a resected nodule were the same as those of the original lung cancer, we categorized the nodule as a metastasis of that lung cancer rather than as a second primary lung cancer of the same histopathologic type.
Although the numbers of patients in this study with each type of primary malignancy were relatively small, there was a diverse representation of different cancers. The small numbers of certain primary malignancies at least partly reflect the overall low prevalences of these cancers in the general population, as well as the fact that certain cancers, such as cervical, ovarian, pancreatic, liver, or biliary tract cancer, are relatively less likely to metastasize to the lungs.
In summary, the likelihood that single or multiple pulmonary nodules resected at VATS will be malignant is higher in patients with a known primary malignancy. In patients with a known primary malignancy such as lung or colorectal cancer or in those in which multiple pulmonary nodules are resected at VATS, the probability of at least one resected pulmonary nodule being malignant is high. Nodules larger than 1 cm are more likely to be malignant than are smaller nodules, regardless of whether an underlying malignancy is known at the time of VATS; the likelihood of malignancy is even higher if the patient has a known malignancy.
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Footnotes |
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Author contributions: Guarantor of integrity of entire study, M.S.G.; study concepts and design, M.S.G., L.H.S., D.M.P.; definition of intellectual content, M.S.G., L.H.S., D.M.P.; literature research, M.S.G., S.K.G., B.D.G.; data acquisition, M.S.G., S.K.G., B.D.G.; data analysis, M.S.G., H.H.Y.; statistical analysis, M.S.G., L.H.S.; manuscript preparation, M.S.G.; manuscript editing, M.S.G., L.H.S., D.M.P.; manuscript review, all authors.
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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