Interest of sentinel node biopsy in apparently intrathyroidal medullary thyroid cancer: a pilot study

Initial surgery for medullary thyroid cancer (MTC) with no evidence of lymph node involvement in neck compartments consists of total thyroidectomy and prophylactic central neck dissection. This study evaluated the reliability of a radiotracer technique for the intraoperative detection of sentinel lymph nodes (SLNs) in lateral compartments in patients with early MTC.

Patients with limited (cT1 N0) MTC entered the study (2009-2012). A 0.1-0.3 ml suspension of macrocolloidal technetium-99-labeled human albumin was injected (under echo-guide) in the tumor 5 h before surgery. Preoperative lymphoscintigraphy confirmed the identification of SLNs in the lateral neck. The operation consisted of total thyroidectomy and central neck dissection, and a hand-held gamma-probe (Neoprobe) guide was used to remove the SLNs from the lateral neck.

Four patients were recruited. The tracer always indicated a SLN. Pathology reports indicated micrometastases from MTC in SLN in three patients. At a mean follow-up of 30.5 months, all patients were biochemically cured. The technique we describe to detect and remove neck SLN from MTC seemed to be very accurate. It always showed the SLNs (usually two) in the lateral compartments. Micrometastases were detected in three of four patients, allowing their correct staging.

The method described here for the detection of SLNs in early MTC seems effective and reliable and can be used for a more precise N staging of the patients. It could play a role, alone or combined with other techniques, in driving the extent of prophylactic neck dissection or other potential applications.