Differential uptake of 125i− and 99mtco4− in a histologically unusual metastatic thyroid carcinoma

A case is presented of a histologically unique thyroid carcinoma metastatic to cervical lymph nodes which concentrated 99mTcO4− to a significantly greater degree than 125I−. This phenomenon may be related to 1. a decreased ability of the tumor to organify iodine, 2. an increased rate of turnover of the iodine-labeled hormone by the tumor, or 3. the unusual “angiomatoid” pattern of the tumor and the difference in the blood levels of the two tracers at the time of the scans. Hot pertechnetate nodules must be rescanned with radioiodine.