Koos Boeve

15 General introduction and scope of this thesis locations. The SLNB procedure (Figure 3) consists of a peritumoral injection of a radioactive tracer one day before surgery followed by imaging of the tracer using lymphoscintigraphy on the same day as the injection [18,26]. During surgery, the SLN is detected and harvested with a small incision and a handheld gamma-probe. Postoperatively, the SLN is assessed by a pathologist for the presence of lymph node metastasis. The small number of lymph nodes in a SLNB specimen (~2) compared to the high number of lymph nodes in an END (~20) [29], allows an extensive pathological work-flow with step-serial-sectioning and an immunohistochemical keratin staining of all slides in addition to the conventional hematoxylin-eosin (HE) staining (Figure 3). Step-serial-sectioning and keratin staining are not part of the END pathological work-flow. Figure 3: The sentinel lymph node biopsy procedure. The sentinel lymph node biopsy (SLNB) procedure consists of a preoperative peritumoral injection of a radioactive tracer (1, crosses indicate injection sites around the tumour which is marked by a dotted line), visualisation of lymphatic drainage patterns and sentinel lymph node (SLN) location by static and dynamic lymphoscintigraphy (2) and SPECT-CT scanning (3). Intra -operatively, SLNs are identified and harvested using a handheld gamma- probe and a small incision (4). The assessment of only a few lymph nodes in a SLNB specimen enables extensive histopathological examination with step-serial-sectioning of six slides (5), conventional hematoxylin-eosin (6) and additional keratin immunohistochemistry (7) that contributes to the detection of small metastasis with a size of isolated tumour cells (<0.2 mm). [Copyright © Koos Boeve, UMCG, 2019 Groningen]