['Several studies have demonstrated overexpression of the mononuclear phagocytic growth factor colony-stimulating factor-1 (CSF-1) and its receptor (CSF-1R) in breast, ovarian, and endometrial adenocarcinomas, and their expression in each of these cancers is strongly correlated with poor prognosis. In addition to adenocarcinomas, sarcomas that are highly malignant arise at much lower frequency in the uterus. Given the common organ of origin and hormonal environment of the adenocarcinomas, we evaluated the potential role of CSF-1 and CSF-1R in the genesis of these tumors using immunohistochemical methods.', 'Immunohistochemical analysis was performed on 19 archival uterine sarcoma samples. Affinity-purified rabbit anti-CSF-1 antiserum (R52) and human cross-reactive murine anti-c-fms antibody were used. In the 19 cases evaluated for CSF-1 immunoreactivity, 42.1% had staining in less than 25% of the tumor, 36.9% had staining in 25-50% of the tumor, and only 21% had staining in greater than 50% of the tumor. When present, the majority of the CSF-1 immunostaining was associated with the extracellular matrix. There was variable intensity in CSF-1 expression: 52.6% had negative to mild staining, and 47.4% had moderate to strong staining. Immunostaining for the CSF-1R revealed that 52.6% of tumors had expression in less than 25% of cells, 21.0% had expression in 25-50% of the tumor, and 26.4% had staining in greater than 50% of the tumor. There was variable intensity of CSF-1R staining. Slight staining was found in 31.6% of the cases, moderate staining was found in 47.4% of the tumors, and 21.0% of the cases had strong expression. There was no statistically significant correlation between CSF-1 and CSF-1R expression and stage, estrogen/progesterone receptor status, number of mitoses per 10 high-power fields, or disease outcome. In addition, overall expression and intensity of CSF-1 and CSF-1R did not predict tumor virulence or disease outcome.'] Do colony-stimulating factor-1 and its receptor have a role in the pathogenesis of uterine sarcomas?