Chondroid hamartoma presenting as solitary pulmonary nodule: Results of dual time point 18F-fluorodeoxyglucose-

To the Editor: The dual time point fluorine 18-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) characteristics of chondroid hamartoma presenting as solitary pulmonary nodule is described in this report. Hamartoma derives from the Greek word hamartia: sin. A 45 years old female was referred for 18F-FDG-PET study in whom contrast enhanced computed tomography (CT) scan of thorax demonstrated a well defined soft tissue density mass in the anterior segment of left upper lobe of 4x3cm that showed contrast enhancement (Fig 1). There was no evidence of calcification and/or necrosis in the lesion. A suspicion of malignancy was raised in the CT report in view of small increase in diameter of the lesion on CT compared to a previous one. The whole body 18F-FDG-PET (Fig. 2a and b) showed mild tracer uptake at baseline 18F-FDG-PET and standardized uptake value maximum or SUVmax1 1.9, which decreased further in the delayed image SUVmax2 1.2. This was a decrease of 36.84% compared to baseline value, (SUVmax2-SUVmax1) x100/SUVmax1. Another PET study with fluorine 18-fluorothymidine (18F-FLT) on a different day showed negligible tracer uptake (Fig. 3), very faintly appreciable visually in the standard gray scale. Overall, both functional imaging examinations were highly suggestive of a benign lesion. Computed tomography guided fine needle aspiration cytology of the lesion was confirmatory of benign chondroid hamartoma (Fig. 4). Pulmonary hamartomas constitute 5%-8% of all solitary lung tumors and about 75% of all benign lung tumors. They have little or no malignant potential, and most of them are asymptomatic. They are composed of tissues that are normally present in the lung, including fat, epithelial tissue, fibrous tissue, and cartilage. However, they exhibit disorganized growth [1]. Accurate imaging interpretation and diagnosis are important because bronchogenic carcinoma is an important differential diagnosis [2]. Frequently they are discovered as an incidental coin lesion on a routine chest radiograph [3]. Popcorn calcification is virtually diagnostic on chest X-rays [3]. It is important to appreciate that a CT scan may be often inconclusive especially if the hamartoma atypically lacks cartilage and fat cells. In a recent report of squamous cell carcinoma developing in the setting of pulmonary hamartoma, hypermetabolism was noted in only half of the mass that correlated with the site of malignancy in the lesion [4]. Imaging by both labelled somatostatin analogue technetium 99m-depreotide (99mTc-depreotide) and thallium 201chloride can also be helpful in excluding malignancy [5]. As for treatment, peripheral tumors are usually simply observed after diagnosis; central tumors may be excised. Overall prognosis is excellent, though there are rare reports of malignant transformation [6, 7]. The importance of partial volume corrected SUV and uptake in the reticuloendothelial system has been emphasized in the literature to differentiate false positive studies for lung carcinoma in various benign conditions [8-11]. Partial volume correction of SUVs is of particular value in small malignant lesions where it aids in accurate assessment of disease activity and estimating the correct SUV [9]. Dual time point 18F-FDG-