Comparison of MR Imaging and Dual-Energy CT for the Evaluation of Cartilage Invasion by Laryngeal and Hypopharyngeal Squamous Cell Carcinoma

False-positive findings for thyroid cartilage invasion on MR imaging in a 59-year-old man with hypopharyngeal cancer. A, T2-weighted MR image obtained at the glottis level shows a tumor (T) arising from the right piriform sinus with intermediate signal intensity. The adjacent posterior right thyroid lamina also shows an area of intermediate signal intensity (arrow). B, T1-weighted image shows that the tumor (T) has low signal intensity, whereas adjacent thyroid cartilage has similar signal intensity (arrow). C, Contrast-enhanced fat-suppressed T1-weighted MR image shows similar contrast enhancement of the tumor (T) and adjacent thyroid cartilage (arrow). A weighted-average image does not show erosion or lysis at the same level (D, soft-tissue window; E, bone window). F, Iodine overlay image shows enhancement of tumor (T) more clearly and is not used for the diagnosis of cartilage according to the findings of the WA image. G, A micrograph of the corresponding axial slice of the surgical specimen at the same level shows that the squamous cell carcinoma cells do not permeate into the right thyroid cartilage lamina (hematoxylin-eosin stain; original magnification, ×5). H, Magnified photograph (square in G) of the posterior part of the right thyroid cartilage lamina with enhancement on MR imaging shows moderate infiltration of lymphocytes into the medullary space, accompanied by fibrosis and aggregation of macrophages, without tumor (H&E stain; original magnification, ×200).