Simple SummaryCutaneous squamous cell cancer is a common form of cancer. Caught early, it is usually curable. However, 3–5% develop into a metastatic form with a very poor prognosis. All efforts to find biomarkers, in blood or in the tumor itself, for early identification of this group of patients have so far failed. This study describes a novel method based on fine needle aspiration that enables the identification of lymphocyte markers in tumor-draining lymph nodes. By focusing on lymph nodes as a key organ for a well-functioning immune system, it might be possible to, early on, find biomarkers related to future metastatic development.AbstractCutaneous squamous cell cancer (cSCC) is the second most common form of skin cancer, characterized by abnormal, accelerated growth of squamous cells. When caught early, most cSCCs are curable. About 5 percent of the cSCC cases have advanced to such an extent, generally metastatic, that they are far more dangerous, with very poor prognosis and challenging to treat. All efforts to find biomarkers, in blood or in the tumor itself, for early identification of patients with a risk for metastasis have so far failed. The present study describes a novel method that enables the identification of lymphocyte markers in tumor-draining lymph nodes. Six patients with advanced cSCC were analyzed using a combination of a sentinel lymph node biopsy (SLNB) protocol, fine needle aspiration (FNA), and flow cytometry. Immunological results from the sentinel nodes were combined with corresponding data from peripheral blood and unfixed tumor tissues. The result demonstrates a striking difference between the subsets of T-cells from the three compartments. Our interpretation of this first pilot study is that the ability to follow specific immunological markers on lymphocytes in tumor-draining lymph nodes will enable the identification of novel prognostic biomarkers not detectable in material from blood and tumor tissues.