Histopathological work-up and interpretation of sentinel lymph nodes for vulvar squamous cell carcinoma

Abstract

Identification / removal of sentinel lymph nodes (SLN) aims at reduction of long-term morbidity from complete lymphadenectomies e.g. inguinal seromas in vulvar squamous cell carcinoma (SCC). Correct histopathological work-up of SLN is imperative, as patients with inguinal recurrence / disease have a high risk to die from systemic disease. Work-up and interpretation of SLN from vulvar SCC differs from that in other organs, in particular from breast cancer. Methods: The experience with SLN dissection and work-up of 48 patients with vulvar SCC at the Institute of Pathology, Medical University Graz, Austria, is presented. Results: All lymph nodes identified after injection of radioactive tracers / blue dye (1–4) were removed in a “same-day procedure“. After frozen section, all SLN were formalin-fixed, sectioned entirely at 250µm intervals for 3 HE-stains and 1 unstained slide for immunohistochemistry / millimeter. In the absence of metastases on HE sections, ALL unstained slides are submitted for immunohistochemistry with antibody to cytokeratin (CK). SCORING IS POSITIVE EVEN WHEN ONLY INDIVIDUAL CK-POSITIVE CELLS & DEBRIS ARE IDENTIFIED. 13 SLN from 48 SCC (34 pT2, 9 pT1b, 5 pT1a) had obvious metastases on HE stains. After CK-staining, 28/35 SLN remained negative and 4 SLN revealed micro-metastases. 3 SLN showed only individual single CK-positive cells & debris. In 1 of these 3 patients, the SLN was called “negative“ and the patient developed conglomerate metastases within 9 months. All metastasis to SLN were from pT2 SCC. Conclusion: SLN dissection for vulvar SCC is a safe procedure for the patient, but requires a careful and complete histopathological work-up of all removed SLN and a correct interpretation of the staining results.