Unusual Thallium-201 and Sonographic Patterns in a Thyroidectomized Papillary Thyroid Cancer Patient with Cervical Nodal Involvement: A Case Report and Literature Review

A 26-year-old woman who had received a thyroidectomy due to papillary thyroid cancer was recently found to have abnormal serum thyroglobulin levels and was referred to our Department for a cancer work-up. The early (10 min) phase thallium-201 ((superscript 201)TI) scan showed increased uptake in the right lower neck region but it returned to background level in the delayed phase (2 h). The retention index (RI) was -28. The concominent neck sonography showed no abnormality except for a small remnant in the left thyroid bed. (superscript 18)F-FDG PET was negative. However, the patient felt the sensation of a foreign body around the anterior neck region after a 3-week T4 withdrawal. A repeated sonography showed 3 hypervascular, enlarged nodes which corresponded to the previous (superscript 201)TI uptake sites. The largest one measured 2.2×1.2×1 cm in size with central hypervascularity. Metastatic papillary thyroid cancer was further diagnosed by T4 withdrawal (superscript 131)I scan. The increased (superscript 201)TI uptake in the early phase might be due to hypervascularity of the tumor. However, the (superscript 201)TI image patterns appeared to contradict with the usual. Cervical sonography and (superscript 18)F-FDG PET could be negative in above mentioned and patients on T4 settings. Such patterns could be commonly found in relatively benign carcinomas such as well-differentiated thyroid carcinoma and should be interpreted with caution.