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

Abstract

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.

Some Comparative Studies Using 99mTc and 131I in Thyroid Scanning

“…Some investigators are of the opinion that the differences in 99m Tc and 131 I scans are such as to warrant the execution of 131 I scans routinely in cases of "warm" 99m Tc nodules (10). Our conclusions are presented below,…”

“…Thus the false 99m Tc scan may mask a "cold", i.e. cancerous thyroid nodule or thyroid cancer metastases (10,11).…”

The Trapping-Only Nodules of the Thyroid Gland: Prevalence Study

“…Free thyroxine (FT 4 ) and free triiodothyronine (FT 3 ) in serum (normal range 7.7-19.3 pmol/L for FT 4 pmol/L for FT 3 ) were measured by radioimmunoassay according to Romelli et al (27). Serum TSH was measured by a sensitive immunoradiometric assay; the results are given in units of the 80/558 reference preparation of the World Health Organization (normal range 0.4-4.5 mU/L).…”

“…In 1970, Steinberg et al described a patient with a malignant thyroid nodule appearing hot when imaged with pertechnetate at 60 minutes; however, an radioautograph of the excised tumor showed that the tissue had not retained radioiodine administered 3 days before surgery (2). In the immediately following years, several reports described patients bearing nodules that were hot on early pertechnetate image and cold on late (24 hours) radioiodine images; these reports included seven benign and six malignant nodules (1)(2)(3)(4)(5)(6)(7)(8)(9). The explanation usually provided was retained trapping capability for monovalent anions with loss of capacity to organically bind iodine (1,6).…”

Radionuclide Angiography for the Diagnosis of Thyroid Cancer

“…This has been discussed in detail in recent litera¬ ture. [19][20][21][22][23][24][25][26][27][28][29][30] In summary, radionuclide angiography of the thyroid is a simple and noninvasive procedure and can be performed in conjunction with the conventional static scan. It improves the specificity of the conventional thyroid scan and it is useful for diagnosis of thyroid cancer.…”