INTRODUCTION:Positron emission tomography (PET) is often used in the evaluation of lung nodules and masses. Despite the widespread use of PET, there are limitations to its interpretation.
CASE PRESENTATION:A 71 year old Uruguayan male with a past medical history significant for coronary disease and tobacco abuse (96 pack year history) presented for evaluation of a chronic cough of 1 to 2 years. He describes his cough as occasionally productive of yellow sputum with sporadic streaky hemoptysis. He denied exposure to tuberculosis and had a negative PPD in the past. Discontinuation of his ACE inhibitor did not resolve the cough. Physical exam was significant for crackles at the right base. Pulmonary function testing was normal. Chest imaging revealed an irregular density in the right lower lobe. By report, he had a normal chest xray in Uruguay in 2004. CT and PET imaging revealed a 5.5 × 2.0 cm mass in the right lower lobe with a standardized uptake value of 4.8. CT imaging also revealed a 1.4 × 1.7 cm subcarinal lymph node. The patient underwent transbronchial biopsies and needle aspirations which were non-diagnostic. Because of the concern for malignancy, the patient underwent a surgical lung biopsy which revealed the mass to be a toothpick with surrounding marked interstitial fibrosis and bronchocentric dense lymphoplasmacytic infiltrate with no evidence of cellular atypia or malignancy. This was consistent with a reactive process. The toothpick was removed and since then, the patient’s cough has resolved.
DISCUSSIONS:Foreign body aspiration often occurs, however, aspiration of a toothpick is a rare event. It has been reported in a canine which developed a cutaneopulmonary fistula. We present the first case of an aspirated toothpick which was PET positive and therefore, in an ex-smoker, highly suspicious for malignancy. PET is often utilized to address the difficulty in differentiation between malignant and benign pulmonary nodules and masses. The most commonly used tracer in PET imaging is (18) F-fluorodeoxyglucose (FDG), whose uptake is increased in most types of cancers. Despite this, FDG is not specific for malignant cells. False positive results in benign conditions often confound PET interpretation. Inflammatory cells such as neutrophils and activated macrophages at infectious and non-infectious sites often display increased FDG uptake. Common examples include infectious processes such as tuberculosis, cryptococcosis, paragonimiasis, and pneumocystis. Noninfectious conditions may also lead to PET positivity. These include, but are not limited to, radiation fibrosis, hyperplastic bone marrow, post surgical changes, pneumoconiosis, and foreign bodies. In the literature there have been few cases of foreign bodies presenting as PET positive masses, and most of them have been post-surgical. Examples include a retained abdominal surgical sponge and a pulmonary suture.
CONCLUSION:We present the first case of a patient who unknowingly aspirated a toothpick and later presented with a PET positive mass that was highly suspicious for malignancy. Our case is another example of the limited specificity of PET scans which are used with increasing frequency in the evaluation of lung nodules and masses. Awareness of conditions that may generate false positive results will aid the clinician to more accurately interpret PET results.
DISCLOSURE:Mohamed Elsawaf, No Financial Disclosure Information; No Product/Research Disclosure Information