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01-06-2013 | Interesting Image
A Papillary Thyroid Tumor Detected by 18F-FDG-PET/CT in a Pediatric Patient with Cowden Syndrome
Published in: Nuclear Medicine and Molecular Imaging | Issue 2/2013
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We describe a papillary thyroid tumor detected by fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in a 11-year-old male patient with Cowden syndrome. 18F-FDG-PET/CT was performed for restaging of a germ cell tumor previously treated. A focal area of increased 18F-FDG uptake in the right thyroid lobe was detected. Based on this PET/CT finding, the patient underwent an ultrasonography guided fine needle aspiration biopsy which showed the presence of a papillary thyroid carcinoma. In this rare case of Cowden syndrome 18F-FDG-PET/CT has been useful in the early detection of a pediatric thyroid cancer (Figs. 1 and 2).
Fig. 1
We report the case of a 11-year-old male patient affected by Cowden syndrome (CS) which is a rare inherited disorder characterized by multiple hamartomas and an increased risk of certain forms of cancer [1]. The patient underwent fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) for restaging of a germ cell tumor previously treated with surgery and chemotherapy. Before 18F-FDG injection, the patient had fasted for at least 6 h; at the time of the radiopharmaceutical injection, the patient presented with blood glucose levels corresponding to 88 mg/dL. Images were acquired 1 h after intravenous injection of 190 MBq of 18F-FDG according to the body mass index. The unenhanced CT scan was performed from the skull base to the inguinal region with a voltage of 120 KeV and tube current of 30 mA. This scan was used for the anatomic localization and the attenuation correction of PET data. PET scan was acquired in 3D mode (multiple bed positions, 3 min for each bed position). Iterative reconstruction and CT-based attenuation correction were used. Whole-body maximum intensity projection (MIP) 18F-FDG-PET image (a) showed diffuse uptake in the large bowel and in the bone marrow, related to inflammatory bowel disease (diagnosed by endoscopy) and bone marrow post-chemotherapy activation, respectively. Increased nonspecific 18F-FDG uptake corresponding to the muscles of the oral cavity was also detected (white arrow). Furthermore, a focal area of increased 18F-FDG uptake was revealed in the neck (red arrow). 18F-FDG-PET (b), unenhanced CT (c) and fused PET/CT images (d), in axial, sagittal and coronal projection showed a focal area of increased radiopharmaceutical uptake corresponding to the right thyroid lobe (red arrow) with a maximal standardized uptake value of 4.1
Fig. 2
Based on these PET/CT findings, the patient underwent an ultrasonography guided fine needle aspiration biopsy which showed medium to large cells with clear vacuolated nuclei and squamoid cytoplasms. These findings were suggestive for a papillary thyroid carcinoma. Therefore, the patient was referred for thyroidectomy. CS is a rare inherited condition characterized by multiple hamartomas in a variety of tissues. It is a cancer predisposition syndrome with an increased risk of developing malignancy in many tissues but especially breast, thyroid and endometrium. It is inherited in an autosomal dominant manner with about 80 % of patients having a germ-line mutation of the PTEN tumor suppressor gene [1‐4]. Although the majority of papillary and follicular thyroid carcinomas are sporadic, also familial forms of differentiated thyroid cancer exist such as those associated to CS [5‐7]. A previous report described the usefulness of 18F-FDG-PET/CT in differentiating multifocal gastric carcinoma from extensive benign gastric polyposis in an adult patient with CS [8]. In our case, 18F-FDG-PET/CT has been useful in the early detection of a papillary thyroid carcinoma in a pediatric patient with CS. The malignancy risk of focal thyroid incidentalomas (FTIs) detected by 18F-FDG-PET/CT is about 35 % [9, 10]. Anyway, this risk may increase when FTIs are detected in patients with genetic syndromes predisposing to familial thyroid cancers
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