Segregation and fusion interphase FISH are two frequently used methods to detect chromosomal abnormalities for lymphomas and leukemia. Previously we demonstrated that Cyclin D1/CEP11 ratio FISH (rFISH) is highly sensitive in the diagnosis of MCL. However, this is an indirect approach and has shown about 10% false negative results based on corresponding flow-cytometry (FCM) and histology due to the fact that t(11;14)(q13;q32) may occur without splitting of cyclin D1. Fusion FISH (fFISH) by directly detecting the t(11;14)(q13;q32) fusion signal, avoids the false negative rate by rFISH. In this study we performed paired rFISH and fFISH on 15 peripheral blood (PB) and 24 bone marrow (BM) samples from patients with confirmed MCL. At least one fusion signal >14% was determined as a cut off by testing PB lymphocytes from 40 normal individuals. Of 39 samples tested, 23 (59%) were fFISH+. However of these 23, only 12 (52%) were rFISH+. Of 11 samples with confirmed positive histology and FCM, 10 (91%) were fFISH+, 7 (64%) were rFISH+. The percentage of cells with fusion signal for fFISH ranged from 2% to 82.5% with predominantly single fusion signal. The percentage of double fusion signals increased dramatically only when rFISH ratio > = 1.10. Our study showed that fFISH is more sensitive than rFISH and therefore is better for the detection of minimum residue disease (MRD). Although double fusion, an indication of reciprocal t(11;14)(q13;q32) translocation is more specific, single fusion is as important as double fusion in the diagnosis of MCL. The use of fFISH will significantly increase our power to detect MRD with t(11;14)(q13;q32) in patients with MCL. 

*This abstract has been submitted to 92nd Annual Meeting of American Association for Cancer Research, New Orleans,March 24-28,2001

Figure 1. Interphase fFISH from MCL patient with negative rFISH result showing fusion signal between CCND1 (11q13, orange) and IgH(14q32, green).	Figure 2. Interphase fFISH from a MCL patient with positive rFISH result showing either single and double fusion between CCND1 (11q13, orange) and IgH(14q32, green).