The CCND1 break apart probe is designed to detect chromosomal rearrangements involving the CCND1 gene on chromosome 11. The CCND1 gene encodes a cyclin D1 protein and functions as a cell cycle regulator1. Chromosomal rearrangements involving the CCND1 have been identified in a variety of cancers and hematological malignancies. Rearrangements of the CCDN1 gene result in CCND1 overexpression and cell cycle deregulation2. CCND1 gene rearrangement involving the immunoglobulin heavy chain (IGH) gene results in CCND1 overexpression and is considered one of the critical pathogenetic features in mantel cell lymphoma1. CCND1 overexpression due to CCND1/IGH rearrangement has also been found in the multiple myeloma, and is identified in 25-50% of MM cases3. Conventional cytogenetic techniques such as fluorescent in situ hybridization (FISH) can be utilized to identify chromosomal rearrangements involving the CCND1 gene.