Clinical evaluation of 201thallium chloride scan for thyroid nodule.

Thyroid scintigraphy with Tl in the evaluation of nodules was investigated. A Tl scan was performed on 55 patients with thyroid nodules previously scanned with Tc or I. In the case of 16 carcinomas, accumulation of Tl was shown in every case. In addition, some lymph node metastases were depicted. (Accumulation was noted also in some of the metastatic lymph nodes.) Cold defect was delineated in ten cases of colloid and fetal adenoma, although accumulation was shown in four cases of Hürthle and embryonal adenoma. Six cases of degenerative cysts were delineated as cold defect. As for colloid nodular goiter, the affinity to the individual nodule was not constant. In general, degenerative and cystic nodules showed less activity and hyperplastic solid nodules showed more activity than normal tissue. We concluded that although a Tl scan cannot differentiate between benign and malignant tumors satisfactorily, it is nevertheless useful for determining surgical indication, as the case showing Tl accumulation on the scan is malignant or benign tumor with poorly differentiated solid type and possiblility of further growth and malignant change.