c-Fos is a proto-oncogene that plays an important role in many cellular functions and has been found to be overexpressed in a variety of cancers. It is involved in important cellular events, including cell proliferation, differentiation and survival which makes its dysregulation an important factor for cancer development. In osteosarcoma and endometrial carcinoma, c-Fos overexpression was associated with high-grade lesions and poor prognosis.