14q32 Abnormalities and 13q Deletions Are Common in Primary Systemic Amyloidosis Using Cytoplasmic Immunoglobulin Fluorescence In Situ Hybridization (cIg-FISH).

Background: Primary systemic amyloidosis is an uncommon plasma cell dyscrasia characterized by organ deposition of immunoglobulin light or heavy chain fragments. It is related to the other plasma cell dyscrasias such as multiple myeloma and monoclonal gammopathy of undetermined significance. cIg-FISH on bone marrow plasma cells has become well established in the initial evaluation of myeloma as the t(4;14), t(14;16),13q-, and the 17p- abnormality are of major prognostic value. The corresponding data does not exist in amyloidosis, as there are only three small studies published to date.

Methods: Using a prospectively held dysproteinemia database, we reviewed all cases of amyloidosis seen at our institution who had cIg-FISH or cytogenetics performed as part of their routine clinical testing. Three hundred thirty nine patients were identified with amyloidosis and cytogenetic testing. Of these 69 had cIg-FISH testing results. cIg-FISH was performed with fluorescent-tagged antibodies to kappa/lambda immunoglobulin and FISH probes corresponding to the following anomalies: trisomies 3, 7, 9 and 15; del17p/-17; -13/del13q; 14q32 split; and t(11;14). CCND1/IGH. If an IGH rearrangement was detected that did not involve CCNDI, we also evaluated t(4;14) or IGH/FGFR3 and t(14;16) or IGH/c-MAF. These probes constitute the standard screening panel used in MM at our institution.

Results: The study population had a median age of 61 years with a male to female ratio of 1.6:1. Median follow up time was 13.5 months. By conventional cytogenetics, 88% of patients had no detectable abnormality. In contrast, only 33% were normal by cIg-FISH. The abnormalities demonstrated were 28% 13-/del13q, 42% IgH translocation, 33% t(11;14), and 3% t(14;16). No patients had a -17/del 17p- or t(4;14). Nine patients had del13q/-13 with an IgH translocation, with 7 of these having t(11;14). Both t(14;16) patients had del 13q. A trend towards increased mortality was seen in patient with any abnormality (p=0.11), but this could not be demonstrated for any single abnormality, likely due to lack of statistical power. There was no correlation between renal involvement or cardiac involvement and cIg-FISH results.

Conclusion: The majority of chromosomal abnormalities in amyloidosis are undetected by conventional cytogenetics. With further study, chromosomal abnormalities may carry the same prognostic value in amyloidosis that they currently enjoy in myeloma. This effect may be independent of currently recognized risk factors.