Sentinel lymph node biopsy in papillary thyroid cancer

Objective To investigate the reliability and feasibility of sentinel lymph node biopsy （SLNB） of papillary thyroid carcinoma using combination of lymphoscintigraphy, the gamma probe and methylene blue staining techniques. Methods Twenty-three consecutive patients with thyroid papillary carcinoma were entered in the study between August 2007 and August 2009. All cases were without clinical evidence of cervical lymph node involvement. The 99Tcm-dextran of 74 MBq （2mCi） was injected intratumorally under ultrasound guidance about 2 h to 5 h prior to surgery. Methylene blue was injected around the tumor during surgery. Preoperative lymphoscintigraphy, intra-operative hand-held gamma probe detecting and methylene blue staining techniques were used to detect the sentinel lymph node （SLN）. SLN biopsies were sent to prepare frozen sections and the results were compared with specimen of routine selective neck dissection. Results The SLNs were identified in all cases with the combination techniques. The SLN identification rates were 87.0% and 100% with methylene blue staining and lymphoscintigraphy plus probe scanning, respectively. Metastases in SLNs were revealed by frozen-section histology in 12 patients. In one case, SLNs frozen-section were negetive, but metastasis was detected in routine histology. In other case both SLN and routine histology were negative, but metastasis was detected in non-SLN （level Ⅵ ） neck dissection. The overall accuracy of the SLN biopsy was 91.3%, positive predictive value 100% and negative predictive value 81.8%. Conclusion The results seem the SLN biopsy technique is a feasible and valuable method for detecting cervical lymph node metastasis and is helpful to decide performing neck dissection in patients with cN0 papillary thyroid carcinoma. Key words: Thyroid neoplasms; Lymph node metastasis; Sentinel node biopsy; Diagnosis