CSF1 and tenosynovial giant cell tumor, diffuse type: In another study, Cupp et al (23) examined 57 TSGCT/PVNS and in all of them found expression of CSF1 mRNA and/or CSF1 protein, including 22 tumors (39%) that lacked a CSF1 translocation, suggesting that alternative mechanisms may lead to upregulation of CSF1.