An odd hot spot

Abstract

We report the case of a 47 year old man with papillary thyroid cancer (PTC) presenting with a toxic thyroid nodule. The patient had lethargy, dysphonia and biochemical hyperthyroidism. Thyroid ultrasound showed a 43 mm nodule in the right lobe, with coarse internal calcification and vascularity. The nodule was hot on technetium uptake scan. Fine needle aspiration (FNA) was recommended given the nodule’s size and presence of calcification. FNA cytology was consistent with PTC. He underwent total thyroidectomy and central neck dissection. Histopathology confirmed a moderately differentiated 50 9 40 9 30 mm PTC replacing the right lobe with metastatic disease in 2 of 6 central compartment lymph nodes. The 2009 American Thyroid Association (ATA) Guidelines do not recommend cytological evaluation for hyperfunctioning nodules, as they are believed to rarely harbour malignancy (1). However, Mirfakhraee et al. reviewed the prevalence of thyroid cancer within solitary hot nodules as reported by 14 surgical case series and found rates of intranodular carcinoma ranged from 0 to 12.5%, with a weighted total mean of 3.1% (2). In children, the risk of differentiated thyroid cancer in hot nodules may be as high as 29% (3). However, no studies have specifically examined the validity of highrisk features (historical and ultrasound) or accuracy of cytology in the diagnosis of toxic thyroid cancers. Hot nodules were specifically excluded from some studies of sonographic predictors of malignancy (4) which formed the basis for the ATA’s recommendations (1). Moreover, increased intranodular vascularity occurs in 73% of all hyper-functioning nodules (5), so should not be considered a risk factor for malignancy in hot nodules. Thus, while the presence of differentiated thyroid cancer in toxic nodules may not be as rare as previously thought, detection remains challenging.