Figure 6b. Infiltrative primary leiomyosarcoma of the thyroid in a 90-year-old woman. (a) Transverse sonogram of the left lobe of the thyroid shows a tumor (between calipers) with infiltration from the posterior tumor margin into the prevertebral space (arrows). (b) Axial unenhanced CT image shows the large size of the tumor and the extent of invasion (arrows). (c) Photomicrograph (original magnification, x 100; hematoxylineosin stain) shows tumor invasion beyond the capsule (arrows).