CSF1 and tenosynovial giant cell tumor, diffuse type: Moreover, combined interphase FISH and CSF1 immunohistochemistry demonstrated that only a minority (2–16%) of the cells in the tumor samples carried the t(1;2)(p13;q37) and that only those cells expressed CSF1, while tissue microarray analyses showed that the CSF1 receptor gene CSF1R is highly overexpressed in TSGCT (20).