Amplification of the MYC gene in immunoglobulin light chain (AL) amyloidosis

We report a woman in her sixties who presented with cardiac involvement of immunoglobulin light chain (AL) amyloidosis, which was categorized into stage IV disease according to the revised Mayo clinic staging scheme. There were no myeloma-defining events at presentation. Although no M-protein was found in the serum, Bence-Jones protein κ was detected in the urine by immunofixation. The bone marrow showed hypocellularity but contained 25.6% plasma cells by examination of aspirate smears, and the cells exhibited cytoplasmic κ light chain restriction by flowcytometry and immunohistochemistry. Fluorescence in situ hybridization and G-banding revealed t(11;14)(q13;q32), leading to the generation of the CCND1-immunoglobulin heavy chain fusion gene. We obtained metaphase spreads that contained a homogeneous staining region on chromosome 8 at band q24, where multiple copies of the MYC gene were localized. However, the majority of interphase nuclei carried 2 or 3 copies of MYC and only occasional cells had four or more MYC signals, suggesting that MYC amplification occurred in a fraction of neoplastic cells. It is therefore possible that the MYC amplification represented intraclonal genetic heterogeneity and diverse subclones in terms of the copy number of MYC were present at presentation.