The impact of sentinel lymph node biopsy on the decision of prophylactic central lymph node dissection in papillary thyroid cancer
İsmail Cem Sormaz1, Onur Bayram2, Yalın İşcan1, İlker Özgür3, Ebru Yılmaz4, Fatih Tunca1, Yasemin Giles Şenyürek1
1İstanbul Üniversitesi, İstanbul Tıp Fakültesi, Genel Cerrahi Anabilim Dalı, İstanbul
2Muş İli, Kamu Hastaneleri Birliği, Muş Devlet Hastanesi, Genel Cerrahi Birimi, Muş
3İlker Özgür; Acıbadem International Hospital, Genel Cerrahi Anabilim Dalı, İstanbul
4Ebru Yılmaz; İstanbul Üniversitesi, İstanbul Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İstanbul
Keywords: Papillary thyroid cancer, sentinel lymph node biopsy, prophylactic central dissection
Introduction: When planning thyroid surgery for patients with papillary thyroid cancer (PTC), prophylactic central lymph node dissection is recommended to eliminate lymph node metastasis that wasn’t detected at the time of diagnosis. However, routine application of prophylactic central dissection is controversial, due to the fact that metastasis can’t be detected by histopathological examination by some papillary cancer patients with routine dissection. Thus prophylactic lymph node dissection on these patients would be an unnecessary intervention. The aim of this study is to evaluate the effect of intraoperative pathological examination for sentinel lymph node (SLN) metastasis diagnosed by preoperative lymphoscintigraphy in deciding for a prophylactic central ganglion.
Material and methods: Data from 21 patients who were operated at Istanbul Faculty of Medicine General Surgery Service A between January 2013–March 2014 with a clinical diagnosis of N0 papillary thyroid cancer and preoperative lymphoscintigraphy were retrospectively reviewed. Demographic datas, complaints, history, physical examination, laboratory results, imaging findings and pathology results were recorded. All patients were diagnosed by preoperative ultrasonography-guided fine-needle aspiration biopsies taken from suspected nodules. All patients had preoperatively an ultrasonography-guided 99m Tc-nanocolloid injection in malign thyroid nodules, followed by lymphoscintigraphy imaging. Following thyroidectomy, an intraoperative gamma probe scan was performed and lesions with highest counts and the ones with a counter of 10% more were considered as sentinel lymph node. These lesions were excised and sent for frozen section examination, followed by a routine prophylactic ipsilateral central lymph node dissection. After the operation, pathology results were retrospectively reviewed and assessed. Metastasis detection in sentinel ganglion was evaluated for sensitivity, specificity, positive predictive value (PPV) and negative prediction value (NPV) with regard to prediction of metastatic disease in central neck area.
Findings: A total of 21 patients were involved; 18 women (86%) and 3 men (14%) with an average age of 44,6 (16 – 67). SLN detection rate by lymphoscintigraphy was 71% (n=15). One SLN in 14 (93%) patients and 2 SLN’s in one (7%) patient were detected and excised. Nine (56%) of these 16 excised SLN’s were detected in pretracheal and 7 (44%) in paratracheal area. Metastatic SLN was detected at frozen section examination of SLN’s that were excised from 15 patients. The group had an average tumour diameter of 15 ± 7,5 mm. A total of 162 lymph ganglions were dissected from central area, of which 35 (21,6%) were metastasic. Central lymph node metastasis was detected in 6 (28%) patients. The metastacity of SLN detected at frozen section examination was confirmed with paraffin examination. During paraffin examination in one of the 2 patients where metastasis was found in SLN with frozen section examination, 17 of 23 lymph nodes taken by SLN were found metastatic. From the other patient, 9 lymph node were removed and one metastatic lymph node was found to be SLN. Among the 6 patients where a SLN couldn’t be detected intraoperatively, 1 patient had metastasis in all 10 dissected central nodes. All patients with an intraoperative non-metastatic SLN detection also had non-metastatic SLN’s detected in their paraffin blocks. However by 3 of these 13 patients (23%), metastasis was detected in non-SLN central lymph nodes. For detection of ipsilateral central area involvement of SLN biopsy by lymphoscintigraphy, the accuracy, sensitivity and specificity values were 81%, 33% and 100% respectively; PPV and NPV were 100% and 79%.
Results: In our study, the specificity and positive prediction values of lymphoscintigraphy with 99mTC-nanocolloid and SLN biopsy on clinical N0 PTC patients to detect central area involvement was found to be high. But the sensitivity rate of this technique was 33%. The poor aspect of this study is the few number of patients. For a better evaluation of SLN biopsy’s effect on N0 PTC patients in determining a SND decision, further studies with a greater number of patients are needed.