Koos Boeve

184 Chapter 9 with a metastasis size <0.2 mm in the 8 th AJCC TNM classification [73]. As a result, in the revised Dutch guideline (in 2017 and 2018) for breast cancer adjuvant axillary treatment (dissection or radiotherapy) is not recommended any more for pN0(i+) SLNs [74]. In chapter 3 [11], 37% of the SLN metastases of OSCC patients had a metastasis <0.2 mm and none of these patients had additional metastases in their neck dissection specimen, hypothesizing that these SLN positive patients might not need a neck dissection at all or only a selective neck dissection, because of the SLN was the only lymph node harbouring metastases. A low rate of additional lymph nodes in the dissection specimen could also be the reason that postoperative pathological assessment with step-serial-sectioning and additional keratin IHC in addition to the conventional HE staining improved the NPV with only 2% (from 94 to 96%) in a prospective trial [35]. In 2017, a study reported about 234 early stage OSCC patients with positive SLNs and reported metastases sizes from 12 other studies [75]. Additional metastases in the non-SLNs from the neck dissection specimen were found in 13% of the patients with ITCs in their SLNs, 20% of the micrometastases and 40% of the macrometastases (>2 mm) [75]. Although metastasis size in the SLNB of OSCC patients might be associated with the presence of metastasis in non-SLNs in the neck dissection specimen, even the incidence of non-SLN metastasis after ITCs in OSCC (13%) is higher compared to the recurrence rate after ITCs and micrometastases in SLNs of breast cancer patients without a lymph node dissection (0.4%) [75,76]. This low recurrence rate in breast cancer could be explained by the adjuvant systemic therapy which is common in breast cancer treatment: nearly all (~96.5%) patients received systemic therapy (chemo- or hormonal therapy) in the trial that compared the SLNB procedure with or without axillary dissection in breast cancer [75,76]. For that reason, the 2018 consensus guideline for SLNB in OSCC patients recommended to consider SLNs with ITCs as positive SLNs and they needs to be followed by a neck dissection [16]. Probably that characterization of genetic and expression profiles of tumour cells of the primary tumor site and of ITCs in lymph nodes might help to select ITCs with or without metastatic potential [67] and contribute to an even more individualised strategy of the cN0 neck in the future. Summarising, the SLNB procedure has a lower accuracy in OSCC of the FOM as a result of the shine-through phenomenon ( chapter 3 ). Therefore the SLNB procedure must be combined with a level I dissection in FOM tumours. Although we reported no additional metastases in cases with an ITC or micrometastases in their SLN, because of the additional metastases rate in other studies, a MRND after a positive SLN with ITCs or a micrometastasis is still recommended.