Interact CardioVasc Thorac Surg 2006;5:446-447. doi:10.1510/icvts.2006.130005
© 2006 European Association of Cardio-Thoracic Surgery
Negative results - Thoracic general |
The false assumption of lung cancer based upon a positive positron emission tomographic scan
John Alfred Carr* and
Jeffrey M. Silver
Northern Illinois Cardiovascular & Thoracic Specialists, 1100 West Central Road, Suite 408, Arlington Heights, IL 60005, USA
Received 31 January 2006;
received in revised form 13 March 2006;
accepted 14 March 2006
*Corresponding author. Tel.: +1 (847) 788-1553; fax: +1 (847) 788-1585.
E-mail address: heartandbones{at}yahoo.com (J.A. Carr).
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Abstract
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Objective: To show that positron emission tomography (PET) can have false positive results from inflammatory lesions. Methods: We present a complicated, elderly patient who underwent an extensive work-up that failed to provide a diagnosis for a radiographic abnormality. Results: A PET scan was positive and the patient was believed to have lung carcinoma until eventual surgical excision was performed. Final pathology revealed that the patient had exogenous lipoid pneumonia. Conclusions: PET scans that are positive cannot be assumed to show a malignancy. Inflammatory lesions will also be positive with PET scanning.
Key Words: Lipoid pneumonia; PET scan; Inflammatory lesion
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1. Case report
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A 71-year-old white male came to the hospital complaining of a productive cough and fever. A chest roentgenogram showed an infiltrate over the right hilum which was suspicious for aspiration pneumonia. His past medical history was remarkable for smoking and severe constipation due to colonic dysmotility, for which he regularly took laxatives and mineral oil. He also had undergone radical neck surgery over twenty years ago for squamous cell carcinoma, followed by radiation therapy. He subsequently developed an esophageal stricture and had chronic dysphagia, being able to tolerate only liquids and pureed food for the past two years, but did not want any intervention.
He was treated for eight weeks with antibiotics, but due to lack of clinical improvement with persistent fevers, a computed tomographic (CT) scan of the chest was performed. This showed a 2 cm nodule in the anterior segment of the right middle lobe (Fig. 1A). CT-guided needle biopsy to diagnose a malignancy was inconclusive. Positron emission tomography (PET) was then performed and was positive with a standard uptake value (SUV) of seven (Fig. 1B). The patient was referred for a lobectomy for lung carcinoma and agreed to undergo resection. Pulmonary function tests were adequate for lobectomy if needed.
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Fig. 1. A. Computed tomographic scan of the chest showing a focal abnormality in the anterior segment of the right middle lobe. B. Positron emission tomographic (PET) scan showing concentrated uptake in the lower right hemithorax. C. High power histologic section showing lipid vacuoles within the lung interstitium separating the alveolar wall from the capillary wall. D. Low power histologic section showing a lipoid mucinous plug occluding a small bronchiole.
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Through a latissimus-sparing, lateral thoracotomy, a wedge excision was performed and the specimen sent to pathology for frozen section. No malignant cells were identified, but a severe inflammatory reaction was appreciated on the slides. The final pathologic diagnosis was exogenous lipoid pneumonia from mineral oil aspiration. Lipid vacuoles could be seen filling the interstitial spaces between the alveoli and the capillary walls (Fig. 1C). Concretions of mucus and oil filled the smaller airways (Fig. 1D). The patient made an uneventful recovery, his esophagus was dilated, and he returned home after three weeks.
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2. Discussion
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Although PET scans are becoming very popular to diagnose lung cancer, they are reported to have a sensitivity of only 79–89%, a specificity of 82–92%, positive predictive value of 40–100%, and a negative predictive value of 75–100% [1–3]. Thus, the thoracic surgeon will often be called to provide a diagnosis and determine the presence or absence of cancer. Inflammatory lesions are positive on PET scan and are the most common conditions to masquerade as cancer. These include histoplasmosis, sarcoidosis, bronchiectasis, lung infections and, by our report, lipoid pneumonia.
Lipoid pneumonia is classified as exogenous or endogenous, depending upon the source of lipid. Endogenous occurs secondary to the release of lipid-containing substrate from the degenerating alveolar cell walls of air spaces distal to an airway obstruction caused by lung cancer, benign tumor, or bronchiectasis [4]. The lipid material causes an intense inflammatory reaction within the alveoli. Exogenous lipoid pneumonia is due to the aspiration of lipid-containing material, most commonly mineral oil, oil-based nasal sprays, and cod liver oil [4,5].
Aspiration of mineral oil does not stimulate the cough reflex and has also been shown to impair mucociliary clearance, which allows its egress into the distal airways [4,5]. Initially, mineral oil causes a weak inflammatory response and is emulsified and ingested by macrophages; but with repeated aspiration and increased deposition in the distal airways, an intense inflammatory response is initiated as the oil is walled-off by fibrous tissue and multi-nucleated giant cells [5,6]. Although the aspiration of mineral oil usually occurs in patients with neurologic disorders, swallowing dysfunction, or gastroesophageal reflux, it can also occur in those without any predisposing factors to impaired cough and swallowing [4,6].
The treatment consists of preventing any further intake and correcting the underlying condition if possible. Specific medical therapy with steroids or anti-inflammatory agents has not been shown to be beneficial [5,6]. With cessation of exposure, 86% of patients will improve without any other intervention [7].
We report this unusual case to illustrate the importance of biopsy and pathologic determination of lesions that are positive on PET scan and to add exogenous lipoid pneumonia to the list of conditions that cause the false-positive uptake of 18-fluoro-2-deoxy-glucose.
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References
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Abstract
1. Case report