Merkel cell carcinoma induces lymphatic microvessel formation

Background Merkel cell carcinoma (MCC) is a rare, highly malignant neuroendocrine tumor of the skin characterized by frequent lymphatic metastasis. Objective We sought to identify lymphovascular anatomy and expression profiles of lymphangiogenic cytokines to give an opinion on lymphangiogenesis in MCC. Methods We studied lymphatic microanatomy and lymphangiogenic cytokines in 27 MCC by immunohistology or immunofluorescence (D2-40, lymphatic vessel endothelial hyaluronan receptor [LYVE-1], vascular endothelial growth factor [VEGF] receptor-3, VEGF-C, VEGF-D, Ki67/MiB-1, CD68/PG-M1, CD68/KP1, CD163), Merkel cell polyomavirus–specific polymerase chain reaction, and coanalysis with clinical and histologic data. Results We found a more than 3-fold increase in the mean density of absolute numbers of small lymphatic capillaries (diameter