The most common carcinomas metastasizing to the lung after a recurrence-free interval >5 years were carcinomas of the kidney and endometrium (5 cases each), followed by adenocarcinoma of the colon (3 cases) and breast (2 cases). There was 1 case each of carcinoma of the esophagus, thyroid, larynx, prostate, and ovary. In 7 of 20 cases, the disease-free interval before lung metastasis was >10 years (Table 1).
In 14 patients, late metastases were isolated to the lung, whereas in 6 concurrent metastases were also found in other sites. In the latter group, bone metastases were most common. They were found at the same time as lung metastases in 3 patients (cases 14, 17, and 19) and subsequent to lung metastases in 1 (case 7). Other metastatic sites were lymph nodes (cases 1 and 20), base of tongue (case 1) and pericardium (case 1).
In most patients (13/20), surveillance after resection of the primary tumor was performed purely by clinical follow-up, without radiologic surveillance in the years before detection of lung metastases. Of the 7 patients who underwent chest imaging for surveillance, 6 had chest radiographs and 1 had a chest computed tomography, all of which were negative for lung nodules during the surveillance period. In 5 patients (cases 4, 10, 11, 16, and 18), multiple chest imaging studies performed over a span of several years during the recurrence-free interval had been negative.
At the time of diagnosis of late lung metastases, 12 patients were symptomatic and 8 were asymptomatic. Presenting symptoms in the former group were cough (5), dyspnea (4, including superior vena cava syndrome in 1), hemoptysis (2), and chest pain (1). In the asymptomatic individuals, lung nodules were discovered incidentally on imaging performed for unrelated reasons (5 cases) or during work-up for elevated tumor markers (3 cases—carcinoembryonic antigen in 2, thyroglobulin in 1). Fourteen patients were never-smokers; 6 were current or ex-smokers (cases 5, 6, 11, 12, 16, and 19; pack-years 2.5 to 20, mean 7.9, median 5).
At the time of lung metastasis, 12 patients had multiple lung nodules/masses and 8 had a solitary nodule/mass. In the former group, nodule size ranged from a few millimeters (cases 2, 4, 7, and 17) to 13.9 cm (case 8; this patient also had a 2.1 cm nodule in a different lobe on the same side). In those who presented with a solitary lung nodule/mass, the lesions ranged from 1.3 cm (case 16) to 7 cm (case 9). Three patients had endobronchial extension of tumor.
With respect to radiologic distribution of nodules, 10 cases had a hematogenous pattern favoring metastases, and 3 had a bronchocentric pattern, favoring a lung primary. In the remaining 7 cases, the radiology report did not state where a primary or metastasis was favored.
Of the 20 patients with late lung metastasis, 14 are alive after follow-up intervals subsequent to lung metastasis ranging from 1 to 13 years (Table 2). Of the remaining 6, 2 were lost to follow-up and 4 died after follow-up intervals ranging from 3 months to 3 years after lung metastasis. Of the latter, 2 patients died of progressive disease. The cause of death in the other 2 was likely unrelated to cancer. Six patients were followed without therapy after pulmonary metastasectomy; only 2 of these developed progressive disease. Overall, of the 14 individuals who are alive after late lung metastasis, 4 are in remission with no evidence of disease, 6 are alive with stable disease and 4 have progressive disease. In this group (n=14), the overall duration of survival since initial diagnosis of the nonpulmonary primary carcinoma ranges from 7 to 35 years (median, 14.75 y; mean, 16 y).
Details of the pathologic findings and immunohistochemical profiles are provided in Table 2. The case with the longest recurrence-free interval before lung metastasis in this series is illustrated in Fig. 1. The patient was a 75-year-old man who presented with cough and was found to have a 3.1-cm solitary lung mass (Fig. 1). He had undergone radical nephrectomy for renal cell carcinoma 33 years ago and had been disease-free. The lung mass was resected and found to be a clear cell carcinoma with an immunoprofile consistent with a renal primary.
This retrospective review shows that metastases to the lung from carcinomas of nonpulmonary sites can occur even after prolonged disease-free intervals following resection of the primary tumor. In contrast to prior reports, this study focuses exclusively on the phenomenon of late lung metastasis and demonstrates that this uncommon phenomenon can occur in carcinomas of a variety of primary sites. In some cases in our series, the length of the disease-free interval caused clinicians to fail to consider the possibility of a metastasis and 1 patient was misdiagnosed with primary lung cancer. In others, a pathologically proven diagnosis of metastatic carcinoma was questioned based at least in part on the length of the disease-free interval. Although it is true that most patients with carcinoma who have been recurrence-free for >5 years are unlikely to develop lung metastasis, our findings demonstrate that pathologically proven exceptions to this dictum do exist. In addition, our clinical and radiologic data show that late metastases can occur in patients with clinical risk factors and radiologic features strongly suggestive of primary lung cancer.
There are only sporadic reports of late lung metastasis from carcinomas of nonpulmonary sites in the literature. A study of 15 pulmonary resections for metastases from gynecologic malignancies included 2 cases of endometrial carcinoma that metastasized to the lung as a solitary lung nodule after recurrence-free intervals of 81 months and 110 months.2 In another series of 100 patients with lung metastases from uterine malignancies, 6 were found to have metastases >10 years after diagnosis of their uterine tumor, including 2 in whom lung metastases were discovered at autopsy 15 and 26 years following diagnosis of endometrial adenocarcinoma.3 In reports where pathologic features have been adequately documented, the longest recurrence-free interval between hysterectomy for endometrial carcinoma and subsequent lung metastasis is 17 years.4,5 The phenomenon of delayed lung metastasis from renal cell carcinoma is more widely recognized, although most relapses occur within the first 3 years after diagnosis.6 Miyao et al7 followed 470 patients with renal cell carcinoma who were recurrence-free in the first 10 years after diagnosis. Of these, 30 (6.4%) were found to have a late recurrence after a 10-year disease-free interval, and the lungs were the most common site of metastasis. The longest recurrence-free interval between nephrectomy and lung metastasis was 20 years. Recently, Watanabe et al8 reported a patient who presented with a solitary lung mass 31 years after nephrectomy. To our knowledge, case 5 of our series documents the longest recurrence-free interval ever reported between resection of renal cell carcinoma and a pathologically confirmed metastasis to the lung (33 y). Of the tumors encountered infrequently in this study, adenoid cystic carcinoma is known to be associated with late recurrences and delayed lung metastasis. Late recurrences after a 5-year disease-free interval occur in 26% of cases and delayed lung metastases have been reported after disease-free intervals of as long as 136 months.9,10 In adenoid cystic carcinoma of the upper airway, the longest reported interval before development of lung metastasis is 200 months.11 Late lung metastases from colorectal carcinoma after prolonged disease-free intervals are quite infrequent (0.9%), and there are only a few reports of this phenomenon in carcinomas of the esophagus and ovary.12–14
An interesting observation is that the majority of patients in our series had a favorable outcome even after developing lung metastasis. Overall, 14 of 20 patients are still alive 1 to 13 years after lung metastasis, attesting to the relatively indolent behavior of carcinomas that are detected in the lungs after prolonged disease-free intervals. The association between long recurrence-free intervals, slow tumor doubling time, and favorable outcome has been previously noted,2 but the biological basis of this phenomenon remains unclear. Our morphologic observations failed to provide a compelling explanation other than the low grade of some of the tumors. It is likely that these neoplasms have an unusually low growth rate that might allow microscopic foci of tumor in the lungs at the time of initial diagnosis to remain occult for several years until they grow to a size that can be detected radiologically. Alternatively metastatic tumor foci may remain dormant for many years and subsequently “reawaken,” as has been proposed recently.15
In summary, late metastases to the lung from carcinomas of nonpulmonary sites can occur after prolonged disease-free intervals and may occasionally present as a solitary lung mass mimicking primary lung cancer. Renal cell carcinomas and carcinomas of the endometrium are the most common culprits.
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Keywords:Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
lung; metastatic; carcinoma; adenocarcinoma; nodules; late recurrence