Sentinel lymph node processing in gynecological cancer histopathology and molecular biology

As sentinel lymph nodes (SLNs) are the first nodes receiving drainage from primary tumors, they provide important prognostic information about the nodal status of a tumor. SLN biopsy has modified the lymph node assessment by pathologists. This review highlights the different ways of histopathological and molecular SLN assessment according to the different gynecological cancers. Other than in breast cancer and melanoma, frozen section (FS) analysis of SLN in gynecological malignancies is still considered an important diagnostic tool. Intraoperative evaluation of the SLN allows to determine the need of completing lymph node dissection in case of metastasis. Intraoperative FS has a high negative predictive value (NPV) and is more sensitive than imprint cytology (IC) alone. If on intraoperative examination on FS the SLN is negative, subsequent analysis of the entire lymph node and histological ultrastadification has the potential to detect occult low volume metastases or to ascertain that a SLN is really negative. This reduces the morbidity compared to systematic pelvic and paraaortic lymph node dissection. Inclusion of the entire lymph node tissue in paraffin blocks after cutting it in 2 mm thick slices and histopathological ultrastaging with serial sections provides important prognostic information about the need of adjuvant treatment. Three sections at 200-250 µm seem to identify the majority of micrometastases. This review discusses different histopathological protocols and molecular [qRT-PCR and one-step nucleic acid amplification (OSNA®)] aspects of SLN evaluation in gynecological cancer.