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Case Report |
1 All authors: Department of Diagnostic Radiology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Box 57, Houston, TX 77030.
Received October 3, 2003; accepted after revision November 14, 2003.
Address correspondence to M. T. Truong
(mtruong{at}mdanderson.org).
Case Report
A 76-year-old man with non–small cell lung cancer in the left upper lobe presented for PET–CT staging evaluation. The patient's medical history revealed resection of the right upper and middle lobes 13 years earlier for non–small cell lung cancer. After the operation, he developed hoarseness caused by recurrent laryngeal nerve injury. Teflon injection was performed to medialize the paralyzed right vocal cord.
Staging PET–CT showed hypermetabolic activity in the left upper lobe malignancy with a maximal standard uptake value of 18. Additionally, focal increased uptake of FDG in the region of the right true vocal cord was present with an associated soft-tissue abnormality (Figs. 1A,1B,1C). The maximal standard uptake value in the right true vocal cord was 15. No other sites of abnormal focal FDG uptake were apparent on the whole-body PET scan. Because a primary laryngeal malignancy and metastasis were diagnostic considerations, contrast-enhanced neck CT was performed. Contrast-enhanced neck CT confirmed asymmetry of the soft tissue with amorphous high-density material in the region of the right true vocal cord at the site of the Teflon injection. No contrast enhancement was present in this region (Fig. 1D). Direct laryngoscopy revealed no evidence of malignancy.
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Discussion
In the evaluation of non–small cell lung cancer, integrated PET–CT has been shown to improve diagnostic accuracy of staging, thus influencing therapy and patient prognosis. In addition to staging mediastinal lymph nodes, PET–CT is also useful in the detection of unsuspected extrathoracic metastases. However, with the increased use of PET–CT, many benign lesions that accumulate FDG are detected and can be misinterpreted as malignancies. This increased FDG uptake at the site of Teflon injection could potentially be misinterpreted as a primary laryngeal malignancy or metastasis.
Vocal cord paralysis caused by recurrent laryngeal nerve injury is usually a complication of neck surgery but can also occur at the time of resection of non–small cell lung malignancy [2]. Vocal cord paralysis can result in hoarseness, dysphonia, dysphagia, sputum retention, and aspiration caused by insufficient glottal closure.
These symptoms can be treated by vocal cord medialization to adduct the glottic folds. Medialization can be achieved by external laryngeal framework surgery (thyroplasty) or vocal cord injection using filler materials such as Teflon, autologous fat, or collagen. Teflon injection, first performed in 1962, was the preferred method of treatment for symptomatic vocal cord paralysis for 30 years with more than 1,500 reported cases in the literature. Teflon injection has recently fallen out of favor because of the high rate of complication, including overinjection, implant migration, and granuloma formation [3].
Injected Teflon causes a local inflammatory response, is ingested by multinucleated giant cells, and is surrounded by dense collagenous tissue [4]. Teflon injected into the vocal cord and the associated foreign-body granulomatous reaction are not visible radiographically. However, Teflon is routinely detected on CT and has a characteristic CT appearance. Teflon typically manifests as an amorphous high-density material in the vocal cord that can extend into the adjacent soft tissues [5]. Occasionally, as a complication of migration and extravasation, Teflon can manifest as an endotracheal or thyroid nodule [6, 7]. In terms of radionuclide imaging, FDG accumulation can occur in inflammatory cells [8]. The foreign-body granulomatous reaction incited by Teflon is presumed to accumulate FDG, resulting in a focus of increased uptake in the neck on PET scans. How long this avidity for FDG persists is unknown. However, the patient had the Teflon injection for vocal cord medialization 13 years previously. This persistence of FDG avidity is important because although this procedure is less commonly performed today, it was widely used in the past. Consequently, this finding can still be encountered in patients undergoing FDG PET in oncology and remains a potential false-positive finding unless the cause is recognized.
In summary, Teflon injection in the region of the vocal cord misinterpreted as a primary or secondary malignancy can have significant clinical ramifications and alter staging, management, and therapy. This potential pitfall can be avoided by being aware of this procedure and the characteristic CT appearance of Teflon injection in the vocal cord. Additionally, knowledge of the prolonged FDG avidity in this region, the use of fused PET–CT to precisely localize FDG uptake, and correlation with clinical history are important in preventing misinterpretation.
Acknowledgments
We thank Gloria Mendoza for manuscript preparation and Brooke Lening for imaging photography.
References
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  V.A. Kumar, J.S. Lewin, and L.E. Ginsberg CT Assessment of Vocal Cord Medialization. AJNR Am. J. Neuroradiol., September 1, 2006; 27(8): 1643 - 1646. [Abstract] [Full Text] [PDF]
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 B. F. Branstetter IV, C. C. Meltzer, M. T. Truong, J. J. Erasmus, H. A. Macapinlac, and D. A. Podoloff PET/CT of Teflon Granulomas Am. J. Roentgenol., October 1, 2004; 183(4): 1173 - 1174. [Full Text] [PDF]
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