Reichert, Matthew MD; Bensadoun, Eric S. MD
University of Kentucky Medical Center, Division of Pulmonary, Critical Care, and Sleep Medicine, Lexington, Kentucky.
Disclosure: The authors declare no conflict of interest.
Address for correspondence: Eric S. Bensadoun, MD, University of Kentucky Medical Center, Division of Pulmonary, Critical Care, and Sleep Medicine, Lexington, KY 40536. E-mail: email@example.com
Positron Emission Tomography (PET) with F-18-fluorodeoxyglucose is commonly used in the evaluation of lung nodules; however, there is limited data on the PET appearance of coal worker’s pneumoconiosis (CWP) and its utility for diagnosing lung malignancy in this setting. Six cases of CWP and suspected malignancy are reported. Each patient had at least one nodule >1 cm in diameter for a total of 19 nodules >1 cm. On PET imaging 18 of the 19 nodules were hypermetabolic and five of the six patients had at least one nodule that was PET positive. Based on pathologic data and clinical follow-up, none of the six patients had any evidence of malignancy. In this series, PET imaging was often positive in patents with CWP; however, all were false positives with standardized uptake value measurements in the range that are typically seen with malignant nodules. Due to its high rate of false positives, PET imaging seems to be of limited utility in diagnosing malignancy in patients with underlying coal worker’s pneumoconiosis.
Coal worker’s pneumoconiosis (CWP) results from chronic exposure to coal dust. On imaging “simple” CWP is characterized by small (<1 cm) nodules with an upper lobe predominance. Coalescence or conglomeration of these small nodules to form larger opacities (>1 cm) defines “complicated” CWP, and as these nodules continue to grow the term “progressive massive fibrosis” (PMF) is often used. It is these larger nodules seen in complicated CWP/PMF that sometimes raise the concern for malignancy and can present a diagnostic dilemma.
Although F-18-fluorodeoxyglucose positron emission tomography (FDG PET) imaging has gained widespread use in the diagnosis and staging of lung cancer,1 there is limited data on the PET appearance of CWP and its utility for diagnosing lung malignancy in this setting. This report describes six patients with complicated CWP/PMF and suspected malignancy.
PATIENTS AND METHODS
The medical records of the Multidisciplinary Lung Cancer Clinic at the University of Kentucky were searched for cases of suspected lung malignancy and CWP seen between 2004 and 2007. Six patients were identified and the results of FDG-PET imaging were reviewed. Three patients had a PET/(computed tomography) CT fusion examination, and three patients had PET only. All PET images were obtained after a 60 minutes incubation period of the FDG. In each patient the number of nodules >1 cm in diameter was assessed and all nodules with a standardized uptake value (SUV, calculated as maximum glucose activity in the lesion/injected glucose dose/body weight in kilograms) >2.5 on PET imaging were considered highly suspicious or “positive” for malignancy. PET results were compared with pathologic data and clinical follow-up.
A 60-year-old man, nonsmoker had worked as a driller in a coal mine for over 30 years. He was referred to the thoracic oncology clinic for evaluation of multiple pulmonary nodules which had been identified on chest radiograph and confirmed with CT imaging. Seven nodules greater than 1 cm in diameter were identified. PET imaging demonstrated increased uptake in all seven nodules (SUV: 2.8–4.0) (Figure 1). The patient had a video-assisted thoracoscopic surgery biopsy of the right upper lobe which revealed anthracosilicotic nodules. Follow-up chest CT 1 year later showed no change in the remaining nodules.
A 52-year-old man who had been a coal miner for 29 years was referred to the thoracic oncology clinic due to a history of melanoma and multiple pulmonary nodules on chest imaging. At the time of presentation, he was a current smoker with a 40 pack year history. He had a history of a melanoma (Clark level 2) removed from his right thigh several years earlier. CT demonstrated many subpleural pulmonary nodules and mediastinal adenopathy. Only one nodule was greater than 1 cm in diameter, and none of the nodules demonstrated increased uptake on PET imaging. The patient had an open lung wedge biopsy performed which showed anthracosilocotic nodules.
A 54-year-old man, former 20 pack year smoker, underwent an evaluation for upper lobe pulmonary nodules with associated borderline mediastinal adenopathy on CT chest. The patient had worked as a coal miner for 20 years. There were two nodules, one in each upper lobe, both greater than 1 cm in diameter. Both nodules were positive on PET scan (SUV: 5.3 and 7.2). CT guided core biopsy of the right upper lobe nodule (Figure 2) demonstrated anthracosilicosis with no evidence of malignancy. Follow-up CT performed 1 year after the core biopsy demonstrated a stable appearance of the nodules.
A 67-year-old male smoker with history of esophageal carcinoma was referred for evaluation of multiple upper lobe pulmonary nodules. He had previously worked as a coal miner for 15 years, and was a current smoker with a 100 pack year smoking history. Three years earlier he had been diagnosed with esophageal carcinoma and treated with chemotherapy, radiation, and an esophagectomy. Approximately 3 years after treatment, a CT scan suggested the progression of multiple, previously noted, upper lobe pulmonary nodules. PET imaging revealed multiple positive areas which prompted his referral. He went on to have a bronchoscopy with transbronchial biopsies which demonstrated anthracosilicosis with no evidence of malignancy. He was subsequently followed for additional 2 years with serial CT scans demonstrating a stable appearance in the upper lobe nodules.
A 65-year-old male nonsmoker with a history of coal mining presented for evaluation of multiple pulmonary nodules. CT of the chest revealed multiple nodules with one nodule greater than 1 cm located in the right lower lobe. PET scan was performed and there was increased uptake in the right upper and lower lobes, as well as, multiple areas in the mediastinum. The most significant uptake was identified in the right lower lobe nodule (SUV: 15). A CT guided needle biopsy of the right lower lobe nodule was nondiagnostic. This was followed by a mediastinoscopy with all surgical specimens demonstrating anthracosilicosis. The patient subsequently underwent a right upper lobe wedge resection and right lower lobectomy. All surgical specimens demonstrated anthracosilicotic nodules with no evidence of malignancy.
A 66-year-old male nonsmoker was referred for evaluation of multiple pulmonary nodules and a positive PET scan. He had worked as a coal miner for more than 20 years. His CT imaging revealed two nodules greater than 1 cm in diameter with one in each upper lobe. PET imaging demonstrated increased uptake in both nodules with the highest uptake noted in the right upper lobe nodule (SUV: 11.9). Review of outside records revealed a right upper lobe wedge biopsy had been performed 4 years earlier and had shown anthracosilicotic nodules. This patient has been subsequently followed for an additional 3 years with serial CT scan demonstrating a stable appearance of the pulmonary nodules.
In this series, six patients had a total of 19 nodules >1 cm in diameter seen on CT (Table 1). Fifteen of 19 nodules were located in the upper lobes and the mean nodule diameter for those nodules greater than 1 cm was 1.37 cm (1.0–2.6 cm). Eighteen of the 19 (95%) nodules were positive (SUV >2.5) on PET with a mean SUV of 6.0 (2.8–15). Five of the 6 patients (83%) had at least one nodule that was PET positive; however, all 5 had histologic evidence of anthracosilicosis without malignancy and none have developed malignancy during follow-up. All PET positive nodules were false positives with SUV measurements in the range that is typically seen with malignant nodules. The size of the nodule relative to the degree of hypermetabolism did not seem to be helpful in distinguishing benign from malignant, in fact, the nodule with highest SUV of 15 measured only 1.6 cm in diameter.
Patients with complicated CWP/PMF and concern for coexisting lung malignancy can present a diagnostic dilemma for the pulmonary physician. It is often difficult or impossible to distinguish CWP/PMF lesions from bronchogenic carcinoma based on radiographic findings alone. PET imaging is often recommended in the evaluation of pulmonary nodules1; however, the literature on the utility of PET for the diagnosis of malignancy in the setting of CWP is limited.
In patients with CWP/PMF without malignancy, hypermetabolic lesions on PET imaging have been described.2,3 These reports are few, so the prevalence and the degree of hypermetabolism seen on PET imaging in patients with CWP/PMF have not been well characterized. In the setting of CWP/PMF and suspected lung cancer there are few reports to guide the use of PET imaging. Two single case reports have suggested that PET imaging might be useful in the diagnosis of malignancy in patients with CWP/PMF,4,5 although another small study suggested that the degree of uptake relative to the size of the nodule might be helpful in distinguishing benign from malignant nodules (e.g., smaller nodules with higher uptake would be more likely to be malignant).6
In our series of six patients with CWP, pulmonary nodules >1 cm in diameter frequently demonstrated increased uptake on PET imaging with SUV values in the malignant range. All PET positives nodules were false positives and the degree of uptake relative to the size of the nodule did not appear helpful in differentiating benign from malignant. In clinical practice, nodules with SUV >2.5 on PET imaging are considered highly suspicious for malignancy and will usually have a needle biopsy or surgical biopsy performed. Based on our series, following this approach for patients with CWP/PMF would lead to many unnecessary invasive procedures in patients with benign lesions. Although PET imaging is useful for the evaluation of pulmonary nodules in the general population, it seems to be of limited utility in diagnosing malignancy in patients with complicated CWP/PMF due to the high rate of false positives demonstrated in this series. Careful follow-up with serial CT imaging may be the most appropriate approach in many of these patients with invasive procedures being reserved for those that show nodule growth.
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