Koos Boeve

59 SLNB in early oral cancer examinated according to the SLN protocol in four patients and using standard H&E without IHC or step serial sectioning in 24 patients. MRND lymph nodes were examined using the routine protocol. Histology of all SLNs and primary tumours was revised by a head and neck pathologist (BvdV). Lymph node metastases were classified according to Hermanek; ITC’s <0.2 mm, micrometastasis 0.2-2 mm and macrometastasis >2 mm [18]. Infiltrative tumour border configuration was defined according to the classification of Heerema: small groups or cords of infiltration cells, widespread cellular dissociation in small groups of cells or in single cells and tumor satellites or any size ≥1 mm away from main tumour [19]. 4.59 mm was used as tumour infiltration depth cut-off according to Melchers [20]. Statistical analysis IBM SPSS Statistics 23 (Statistical Package for the Social Sciences, Inc., Chicago, IL, USA) was used for analysis. Categorical data are presented as number (n) and their percentages (%). Associations between categorical data were tested with the Fisher’s exact or Chi-squared test. Continuous data were tested using the Student’s t test or the Mann-Whitney U test for normally or skewed distributed data, respectively. False negative SLNB patients were defined as patients with isolated regional recurrence in the SLNB negative neck side and were used to calculate the sensitivity and negative predictive value. Significant differences were defined as a p-value ≤ 0.05. RESULTS Sentinel lymph nodes were identified in all 91 cases (100%). In total 274 SLNs were harvested with a median of 3 (range 1-11) per patient. The results of the SLN procedures are summarised in Table 1. In all patients, at least one SLN was intraoperatively detected. However, in 4 patients (4%) additional hotspots were noticed besides the harvested SLNs on the SPECT-CT without intraoperative detectable radioactive LNs. In 1 of these 4 patients, the harvested SLN was positive and the neck was treated by MRND in a second operation. The other 3 patients were isolated regional recurrence (IRR) free after 10, 11 and 47 months of routine follow-up. In one patient with a ventral floor of mouth tumour, only a contralateral SLN was identified. The other patients had ipsilateral (n = 57, 63%) or bilateral (n = 33, 36%) located SLNs. Positive SLNs were found in 25 (27%) patients. In 1 patient with a 1 mm metastasis in the SLN routine follow-up was chosen instead of a MRND. This patient was still recurrence free after 23 months. In none of the patients with micrometastases or ITCs in the SLN additional metastases were found in the MRND specimen (Figure 1, Table 2, p = 0.024). Also, none of the 57 non-SLNs harvested during the SLNB were positive. Finally, skip metastases were