Detection of micro-metastases by flow cytometry in lymph nodes from patients with penile cancer

Background: The tumor draining lymph node concept was first described in penile cancer for staging. Immunohistochemistry and histopathology evaluations are routinely used in clinical practice to examine lymph nodes for metastasis. However, these methods are time-consuming with low diagnostic accuracy and micro-metastases might be missed. In this study, we aim to evaluate detection of metastatic cells in draining lymph nodes by flow cytometry. Methods: To assess the sensitivity of micro-metastasis detection by FACS (Fluorescence-activated cell sorting), HeLa cells were titrated into Peripheral blood mononuclear cells (PBMCs) and expression of pan-cytokeratin AE1/AE3 was analyzed. Single cell suspensions were separately prepared from 10 regional lymph nodes obtained from 5 patients with invasive penile cancer undergoing radical surgery and lymph node dissection. Lymph node dereived cells were examined for cell surface expression of EpCAM, E-cadherin and intracellular expression of pan-cytokeratin AE1/AE3 by FACS. Results: Ten lymph nodes from 5 penile cancer patients were investigated in a head-to-head comparison between FACS and pathology examination of sections. All metastatic lymph nodes verified by pathology examination were also identified by FACS. Two additional lymph nodes with micro-metastases were diagnosed by FAGS only. Conclusions: FACS analyses of pan-cytokeratin AE1/AE3 stained single cells from tumor draining lymph nodes can be used to detect micro-metastases in patients with penile cancer patients.