Nguyen, Lai P.

Abstract Introduction: A new isodicentric variant of del(20q) was recently described; namely ider(20)(p11.2)del(20)(q11.2q13.3). The frequency and clinical significance of this anomaly are not yet established. This anomaly is usually missed in routine cytogenetic studies and the common commercial FISH probe, D20S108, does not distinguish between del(20q) and ider(20q). The goals of this study were to determine 1) the frequency and hematopathology of patients (pts) with ider(20q) and 2) the best cytogenetic methods to distinguish among various del(20q) anomalies. Methods: We selected 12 pts referred for chromosome studies with -20,+mar to look for evidence of ider(20q). For comparison, we also randomly selected 12 pts with classical del(20q). Up to 10 bone marrow metaphases were studied for each of these 24 pts using FISH with probes for 20pter, JAG1 (20p12), centromere 20, D20S108 (20q12) and 20qter. We also studied 200 interphase nuclei from each pt using D20S108 and 20qter probes. We reviewed cytogenetic results for a consecutive series of pts in our hematological practice between 9/1/05 and 12/31/05 to establish the frequency of ider(20q). Blood and marrow slides were available for microscopic evaluation in 9 of 12 pts. with ider(20q). Results: By metaphase FISH, each of the 12 pts with del(20q) were 20pter+, JAG1+, D20S108- and 20qter+ indicating an interstitial deletion. Each of the 12 pts with ider(20q) were 20pter-, JAG1-, D20S108-- and 20qter++ indicating an isodicentric chromosome with an interstitial del(20q) on either side of the centromere. The ider(20q) is best detected using probe for D20S108 and 20qter. By FISH each pt with ider(20q) had a mixture of cells with del(20q) and ider(20q), though cells with only del(20q) were not usually detected by chromosome studies. One pt had a subclone with two copies of ider(20q). Interphase FISH identified del(20q) and ider(20q) in each specimen. Hematopathology studies of 9 pts with ider(20q) indicated acute myeloid leukemia (AML) with multilineage dysplasia in 1 and myelodysplastic syndrome in 8 (refractory cytopenia with multilineage dysplasia (RCMD) in 3, RCMD with ringed sideroblasts in 3, atypical myelodysplastic/myeloproliferative disease in 1, and refractory anemia with excess blasts-2 (RAEB-2) in 1). Additional chromosome anomalies were detected in the pts with AML with multilineage dysplasia and RAEB-2. Six pts had dysgranulopoiesis in addition to dysmegakaryopoiesis and/or dyserythropoiesis. Among 5,744 pts in our hematological clinical practice screened by interphase FISH, ider(20q) was seen in 8, but 8 of 78 pts with del(20q) also had ider(20q). Discussion: In clinical practice ider(20q) is common in hematological disorders and occurs in 0.14% of all pts and in 10% of pts with del(20q). This figure may underestimate the true frequency of ider(20q) because novel FISH studies with D20S108 and 20qter are required to confirm its presence. When G-banding preparations indicate -20,+mar, then ider(20q) should be suspected. The literature is sparse but pts with ider(20q) appeared to have a more consistent presentation of multilineage dysplasia with additional involvement of the granulocytic series than pts with del(20q). These results suggest that it is helpful to distinguish among various forms of del(20q) in clinical practice using both chromosome and FISH studies with D20S108 and 20qter.

Abstract Abstract 4238 Background Duplication of the long arm of chromosome 1 (1q) is a recurrent finding in hematologic neoplasms. It is most commonly observed as an unbalanced whole arm translocation with chromosome 7, resulting in concurrent deletion of 7q (ISCN as der(1;7)(q10q10)). It is less frequently observed as an unbalanced translocation with a chromosome other than chromosome 7 or as a duplication of only a segment of 1q. The der(1;7) has been described in myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML), and is reportedly less commonly associated with myeloproliferative neoplasms (MPN). The effect of this rearrangement on prognosis is unclear, although it is classified by the International Scoring System (IPSS) as a karyotypic variant of del(7q)/-7 and is thus assigned poor risk. We have initiated a thorough review of all cases of duplication of the long arm of chromosome 1 seen at our institution. Methods After approval from the Institutional Review Board, all cases seen at Mayo Clinic over a 20 year period (1989-2009) were searched for a duplication of the long arm of chromosome 1. The sole exclusion criterion was a complex karyotype (3 or more independent chromosome abnormalities in the clone). Cytogenetic and hematopathology review was done and relevant clinical data were abstracted from the Mayo Clinic record. Survival of MDS patients and MPN patients was determined from time of cytogenetic diagnosis of der(1;7) until death or last contact with the patient, using the Kaplan-Meier method. Results Among 23,375 unique patients at Mayo Clinic with a cytogenetic study for hematologic neoplasm, 229 (0.98%) patients carried a duplication of 1q. Within this group, 99 (0.42%) had duplication of part of 1q, 123 (0.53%) carried a whole arm duplication of 1q, and 7 patients carried an isochromosome 1q (resulting in 4 copies of 1q). The most common karyotype among those with a whole arm duplication of 1q was der(1;7) (n=84), followed by similar whole arm translocations involving chromosomes 9 and 19 (n=7 each) or chromosomes 12, 13, 14, 15, 16, 17, 18, 20, 21, or 22 (n=1 to 6 each). We focused on 65 der(1;7) patients who had adequate hematopathological material that could be reviewed and sub-classified according to WHO criteria. MDS was identified in 30 patients and MPN in 20. MDS (therapy related, RARS, RAEB-1 or 2) was seen in 9 patients (14%), MDS/ refractory cytopenia with multilineage dysplasia (RCMD) in 19 (29%). MDS/Myeloproliferative neoplasm (MPN) in 2 (3%), MPN not otherwise classified in 5 (8%), and MPN / primary myelofibrosis (including 1 post-polycythemic and one post-thromobocythemic) (PMF) in 15 (23%). The bone marrow was apparently normal in 5 patients (8%), CLL was noted in 3 (5%), and 1 each exhibited features of systemic mast cell disease or myeloma. Acute myeloid leukemia (AML) was identified 5 patients (8%). The M:F ratio of the der(1;7) patients was 2.8:1. The median age at occurrence of the der(1;7) was 63 years (range: 13-87 years). All 5 AML patients have died (median survival 9 months). Of the MDS and MPN patients, the median survival was 2.2 and 2.8 years, respectively, from the time of cytogenetic diagnosis. Overall survival was not significantly different between the MDS and MPN group, and they exhibited 30% survival after 5 years (see Figure). Conclusions Duplication of 1q was observed in nearly 1% of the Mayo Clinic patients who had a bone marrow cytogenetic study for a hematologic neoplasm. Among those with a der(1;7), AML was uncommon but MDS and MPN were similar in frequency. Median survival of 2.2 to 2.8 years for the MDS and MPN group justifies assignment to a more favorable group than the current IPSS assignment. Disclosures: No relevant conflicts of interest to declare.