THY1 and metastatic melanoma: CD90, on the other hand, is generally expressed on thymocytes, neurons, mesenchymal stem cells, hematopoietic stem cells, NK cells, endothelium (mainly in high endothelial venules (HEVs), where diapedesis takes place, renal glomerular mesangial cells, circulating metastatic melanoma cells, follicular dendritic cells (FDC), a fraction of fibroblasts, and myofibroblasts.