Iodine-131 uptake in thymic hyperplasia with atypical computed tomographic features

Intense 18-fluorodeoxyglucose uptake by the thymus on PET scan does not necessarily herald recurrence of thyroid carcinoma

This is the first report of intense fluorodeoxyglucose positron emission tomography (FDG-PET) uptake secondary to thymic hyperplasia during follow-up for thyroid carcinoma. A 36-yr-old woman underwent thyroidectomy for a papillary carcinoma measuring 4 cm in diameter. After two doses of radioiodine, thyroglobulin (Tg) remained detectable following recombinant human TSH (rhTSH) stimulation. A whole body scan (WBS) was negative. On computed tomography (CT) scan, a slightly lobulated thymus was visualized. PET scan showed intense thymic uptake. Following resection, anatomo-pathological analysis showed homogenous hyperplastic thymic gland without neoplastic cells. Two months later, under levothyroxin (L-T4) substitution, Tg was no longer detectable and PET scanning did not show any 18-FDG uptake. This observation suggests that thymic FDG uptake does not necessarily herald recurrence of thyroid carcinoma and must be interpreted with caution in such a setting. Other conditions associated with abnormal uptake by hyperplastic thymus must also be envisaged.

Imaging Evaluation of Pediatric Mediastinal Masses

Mediastinal masses in children are a heterogeneous group of asymptomatic to potentially life-threatening congenital, infectious, or neoplastic lesions that can present complex diagnostic and therapeutic dilemmas. This article presents the imaging features of the common mediastinal masses seen in the pediatric population. Classification of the masses is performed according to the traditional mediastinal compartment model, consisting of the anterior, middle, and posterior mediastinum. This scheme facilitates differentiation of the variety of disorders.