Discordant Tl-201 and Tc-99m imaging in a patient with thyroid carcinoma and Hashimoto's disease.

In a case of Hashimoto's disease complicated by thyroid gland cancer, the primary site of the cancer was visualized as a cold nodule on Tc-99m pertechnetate scintigraphy, as a warm nodule on Tl-201 early imaging, and as a hot nodule on Tl-201 delayed imaging. Generally, Tl-201 shows markedly diffuse accumulation in the lesions of Hashimoto's disease. The warm nodules observed on early scans suggested similar accumulation at the sites of Hashimoto's disease and thyroid cancer. The hot nodules on delayed imaging may be due to the difference in Tl-201 washout time between the sites of Hashimoto's disease and thyroid cancer. There was markedly increased Tl-201 accumulation in bilateral cervical metastatic lymph nodes on both early and delayed images.