Polycomb protein SUZ12 is a nuclear protein belonging to the VEFS (VRN2-EMF2-FIS2-SUZ12) family. It is overexpressed in breast and colon cancer, expressed at low levels in quiescent cells. Expression rises at the G1/S phase transition. A chromosomal aberration involving SUZ12 may be a cause of endometrial stromal tumors. The translocation generates the JAZF1-SUZ12 oncogene consisting of the N-terminus part of JAZF1 and the C-terminus part of SUZ12. It is frequently found in all cases of endometrial stromal tumors, except in endometrial stromal sarcomas, where it is rarer.