Distinguishing Intrathyroid Parathyroid Adenoma from Colloid Nodules and Papillary Thyroid Carcinomas Using Multiphasic Multidetector Computed Tomography.

OBJECTIVE: The aim of the study is to determine whether multiphase multidetector computed tomography (4D-MDCT) can differentiate between intrathyroid parathyroid adenomas (ITPAs), colloid nodules, and papillary thyroid carcinoma (PTC). METHODS: We studied 22 ITPAs, 22 colloid nodules, and 11 PTCs in 55 patients. Hounsfield unit (HU) values of the nodules were measured on 4D-MDCT in the precontrast, arterial, venous, and delayed phases. Raw HU values, phase with peak enhancement, and washout percentages between the phases were evaluated. RESULTS: Regardless of size, all ITPAs (22/22) showed peak enhancement in the arterial phase, which was significantly greater than both colloid nodules (15/22) and PTC (6/11, P = 0.002); thus, nodules with peak enhancement in the venous or delayed phase were not ITPAs (specificity = 1). For nodules with peak enhancement in the arterial phase, the percentage washout in the arterial-to-venous phases separated ITPAs from PTC and colloid nodules (P < 0.001) with greater than or equal to 23.95% loss of HU value implying IPTA (area under curve, 0.79). This left a subset of colloid nodules or PTC that either peaked in the venous or delayed phase or had an arterial-to-venous phase washout of less than 23.95%. From this subset, PTC measuring 1 cm or greater could be separated from colloid based on HU values in the arterial phase with a cutoff HU value less than 81.4 for PTC (area under curve, 0.72) and an HU value greater than 164.5 suggested colloid. CONCLUSIONS: Intrathyroid parathyroid adenomas can be distinguished from colloid nodules and PTC by peak enhancement in the arterial phase and rapid washout. A subset of colloid and PTC measuring 1 cm or greater can be separated using arterial phase HU values.

Thyroid carcinoma metastasizing to the submandibular gland: Sonographic findings.

Metastases to the submandibular gland are extremely rare; a literature search retuned only three previously reported cases from a thyroid gland primary site. Herein, we report two cases of metastatic thyroid carcinoma to the submandibular gland in a 64-year-old woman with PTC and a 70-year-old-woman with medullary thyroid carcinoma (MTC). The metastases were identified on CT and PET/CT in one case and on CT in the other case, but both were diagnosed with ultrasound-guided fine-needle aspiration. Our cases highlight that while rare, both PTC and MTC can metastasize to the submandibular gland.