A spindle cell tumor is a lesion in which the cell morphology is predominantly spindle cells and can be cancerous, but is more often a tumor of mesenchymal origin. The origin of the tumor is very broad and can be of vascular origin, fat origin, fibrous origin, muscle origin or mesothelioma, mesenchymal tumor, etc. There are various possibilities of origin. Therefore, immunohistochemical methods are used to help determine this. As an example, for example, CD31 and CD34 positivity often suggests a possible tumor of vascular origin. If it is DES, SMA positive, it often suggests a possible muscle origin. If it is positive for S100, GFAP, it often suggests a possible tumor of neural origin. If it is positive for CD117 and DOG1, it may be mesenchymal origin. If positive for Calritinin, CK5/6, it may be a tumor of mesothelial origin. Spindle cell tumors generally require immunohistochemistry for definitive diagnosis. positive for CD117 and DOG1 often predicts the possibility of a mesenchymal origin; if positive for Calritinin and MC, it may suggest a mesothelioma origin. Immunohistochemistry for spindle cell tumors is not one-to-one specific; it often requires a combination of multiple immunohistochemistries to be done to help make a good determination. Therefore, spindle cell tumors must be combined with the clinical history, the site of occurrence, and some of its features, and then combined with the immunohistochemical results to finally arrive at a more definitive diagnosis.