Preoperative lymphoscintigraphy and sentinel lymph node biopsy in papillary thyroid cancer. A pilot study

Lymphadenectomy for papillary thyroid cancer is a matter of debate. After showing its usefulness as a prognostic factor in both melanoma and breast cancer, the concept of sentinel lymph node biopsy was also recently applied to differentiated thyroid cancer. To date, all attempts to locate and remove the sentinel node were based on the intraoperative injection of a vital dye. The feasibility and the technical details of using preoperative lymphoscintigraphy coupled with intraoperative vital dye and gamma probe scanning were investigated and discussed.

Six patients diagnosed with papillary thyroid cancer were submitted to preoperative lymphoscintigraphy with (99m)Tc-labelled colloidal albumin at different dosages. The operation consisted in a total thyroidectomy with sentinel lymph node biopsy guided by intraoperative injection of a vital dye (Blu Patent V, 2.5%) and scanning with a hand-held gamma probe. Lymph node dissection was completed in the area in which the sentinel node was located.

The sentinel node was identified using all the three methods in all cases (100%). Considering one of the methods alone, identification rates were 66, 50, and 83% for preoperative lymphoscintigraphy, vital dye, and probe scanning, respectively. One sentinel node was identified in four cases and two in the other two cases. The optimal dosage of the tracer appeared to be at 22 MBq.

These results underline the necessity to use the combination of nuclear medicine imaging and lymphatic vital dye in order to enhance the identification rate of sentinel node also in thyroid cancer. It is now necessary to check the diagnostic accuracy of this procedure through a controlled trial involving a more extended lymph node dissection in the neck.