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Abstract BACKGROUND: DNA rearrangements that result in the inappropriate activation of the PDGFRA gene at 4q12 and the PDGFRB gene at 5q31-q33 occur rarely in patients with chronic myeloproliferative disorders. Approximately 10% of patients with systemic mast cell disease/hypereosinophilic syndrome have a unique mutational mechanism resulting in PDGFRA overexpression due to a novel microdeletion of the CHIC2 region resulting in the juxtaposition of FIP1L1 and PDGFRA. PDGFRB activation has been observed in patients with chronic myelomonocytic leukemia/atypical chronic myeloid leukemia and has been associated with 11 translocation partners. Since patients with demonstrable breakpoints in the PDGFRA and PDGFRB genes often have a dramatic disease response to the tyrosine kinase inhibitor imatinib, we searched the Mayo Clinic Cytogenetic database to identify additional translocation partners involving these regions. METHODS: Homebrew dual-color FISH probes were created which flank the PDGFRA gene at 4q12 and the PDGFRB gene at 5q31-q33. Archived bone marrow karyotypes analyzed in the Mayo Clinic Cytogenetics laboratory from a 15 year period (1989-2004) were reviewed to determine the frequency of specimens with breakpoints at 4q12 and 5q31-33. Of the 29,047 abnormal specimens, 64 possessed a 4q12 breakpoint and 164 possessed a 5q31-q33 breakpoint (excluding simple deletions). Of these 228 patients, residual bone marrow specimens were available from 170 patients for FISH analysis. RESULTS: Eleven of 50 patients with a 4q12 breakpoint yielded a break with the PDGFRA FISH probe. Eight patients had the previously described t(4;12)(q12;p13) which results in a reciprocal exchange between the TEL oncogene and has a break near, but not within, the PDGFRA gene. Three patients had breaks within the PDGFRA gene and had novel translocation partners including 1q44, 3q25 and 17q23. Twelve of 120 patients with a 5q31-q33 anomaly had a break detected with the PDGFRB FISH probe. Nine patients had the classic t(5;12)(q33;p13) involving PDGFRB and TEL. Three patients had novel PDGFRB translocation partners, including 1q21, 14q32 and 16p13.1. CONCLUSIONS: Breakpoints involving the PDGFRA and PDGFRB genes appear to be quite uncommon as only 23 patient samples were abnormal in our series of 29,407 abnormal bone marrow samples. With the description of three new translocations involving PDGFRB, at least 14 unique translocation partners have been identified with this gene. With the exception of the recurrent t(5;12) between PDGFRB and TEL, most translocations involving PDGFRB appear to be unique. The microdeletion of CHIC2 at 4q12 resulting in the juxtaposition of FIP1L1 and PDGFRA has been the sole mechanism thus far described resulting in the activation of this gene. The identification of the three translocations involving the PDGFRA gene represent the first classic cytogenetically visible rearrangements involving this novel gene region. While rare, we propose that all chromosome anomalies identified with breakpoints in the 4q12 and 5q31-q33 regions should receive appropriate FISH testing to determine the potential involvement of the PDGFRA and PDGFRB genes.

Abstract Background: Peripheral blood (PB) is sometimes used in place of bone marrow (BM) for cytogenetic studies in either primary (PMF) or post-polycythemia vera/essential thrombocythemia (post-PV/ET MF) myelofibrosis. In a retrospective study, we examined overall yield from PB cytogenetic studies in MF and where possible compared the results with those obtained by BM cytogenetic analysis. Methods: Standard laboratory techniques were used to perform cytogenetic studies in both the PB and BM. A successful study constituted the acquisition of at least two analyzable metaphases and an abnormal clone required the presence of a specific cytogenetic abnormality in at least two metaphases. Clinical and laboratory correlations were made using variables collected at the time of cytogenetic studies. Results I: A total of 242 PB cytogenetic studies were reviewed to identify 59 MF cases; 39 were PMF and 20 post-PV/ET MF. Median age was 60 years (range 36–77) and 37 were male patients. The median duration of the disease at the time of PB cytogenetic studies was 3.5 years (range 0.2–35). At least two analyzable metaphases (median 20, range 2–31) were obtained in 49 (81%) of the 59 study patients; in univariate analysis, this was predicted by presence and degree of circulating myeloid progenitor cells (p < 0.0001), higher PB CD34 count (p < 0.0001), higher leukocyte count (p = 0.0008), and absence of myeloid growth factor therapy (p = 0.005). In multivariable analysis, only the presence of circulating myeloid progenitor cells sustained its significance. Results II: Twenty two cases had concomitant PB and BM cytogenetic studies performed. Of these, 9 patients had abnormal BM cytogenetic findings; the concomitant PB cytogenetic studies were also abnormal in 5 (56%) patients but normal in the other 4. Conversely, PB cytogenetic studies were abnormal in 12 patients; the concomitant BM cytogenetic studies were abnormal in 5 (41%) and normal in the remaining 7. PB cytogenetic studies were not successful in 4 of the 22 total cases; BM studies were successful in 3 of these 4 cases and the results were normal in all. Conclusion: In the presence of circulating myeloid progenitor cells, PB can be considered as an alternative to BM for cytogenetic studies in MF patients, especially in view of the difficulty getting BM aspirates in this disease. However, considering the prognostic value of specific cytogenetic abnormalities in MF, the non-trivial discordance between the BM and PB cytogenetic findings, observed in the current study, warrants a prospective evaluation for further clarification.

Abstract Background: Deletion 5q is a lenalidomide-sensitive cytogenetic abnormality seen usually in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In the current study, we looked into the occurrence and clinicopathologic correlates of del(5q) in myeloproliferative neoplasms (MPNs) defined according to the World Health Organization (WHO) criteria. Methods: Patients with del(5q)-positive MPN were identified through database query involving over 2000 patients with myeloproliferative neoplasms (MPD) including no less than 500 patients with primary myelofibrosis (PMF), 600 patients with essential thrombocytosis (ET), 500 patients with polycythemia vera (PV), and the remaining comprised of patients with molecularly-undefined chronic eosinophilic leukemia, hypereosinophilic syndrome, systemic mastocytosis (SM), chronic neutrophilic leukemia, and “MPN, unclassifiable”. Results: A total of 23 patients with del(5q) were identified (12 at time of initial diagnosis), suggesting an overall prevalence rate of 1%. A central pathological review was conducted to confirm the diagnosis in each instance. Specific diagnoses included PMF (n=14; estimated prevalence of 3%), MPN, unclassifiable (n=4), PV (n=2), ET (n=1), post ET-myelofibrosis (n=1) and SM (n=1). Del(5q) was a sole abnormality in 5 patients, accompanied by one other abnormality in 6 patients, and part of a complex karyotype in 12 patients. The most common breakpoint was q13q33 (n=10) followed by q15q33 (n=6). Based on sample size adequacy, we focused on del(5q)-positive PMF patients and compared their bone marrow histological and clinical features with their del(5q)-negative counterparts seen at the Mayo Clinic during the same period of time (n=311). There was no difference in gender or age distributions. Histopathological review did not show the typical tight clusters of megakaryocytes seen in classic PMF. The megakaryocytes were not the predominate feature of the biopsy, in general were less lobulated and smaller in size, and had a higher grade of fibrosis (med = 3+) than classic PMF. Furthermore, del(5q)-positive PMF patients presented with significantly lower hemoglobin level (p=0.0009) and platelet count (p=0.0003). The percentage of patients presenting with a hemoglobin level of < 10 g/dL or a platelet count of < 100 × 109/L were 70% and 92% in del(5q)-positive patients as opposed to 43% and 18% in del(5q)-negative patients. However, the presence of del(5q) did not significantly affect either overall survival (Figure) or leukemic transformation in PMF (14% vs 9%). Conclusions: Del(5q) is generally rare in MPNs but might occur in as much as 3% of patients with PMF. The presence of del(5q) does not appear to affect overall survival in PMF despite its clustering with adverse prognostic features for the disease including anemia and thrombocytopenia. Finally, megakaryocyte morphology and distribution in del(5q)-associated PMF are characteristically different from classic PMF. Figure Figure

Abstract Background: Previous cytogenetic studies in polycythemia vera (PV) have included a relatively small number of patients (“n” ranging 10–64). In the current study (n=137), we describe cytogenetic findings at presentation and examine their relationship to clinical and laboratory features, including bone marrow JAK2V617F allele burden. Methods: The study consisted of a consecutive group of patients with PV who fulfilled the World Health Organization (WHO) diagnostic criteria and in whom bone marrow biopsy and cytogenetic studies were performed at diagnosis. Results I: cytogenetic details At diagnosis: A total of 137 patients (median age, 64 years; 49% females) were studied at diagnosis and had adequate metaphases for interpretation. Cytogenetics were normal in 117 patients (85%) and displayed either a sole -Y abnormality in 5 patients (7% of the male patients), and other chromosomal abnormalities in 15 (11%). The latter included trisomy 8 in five patients, trisomy 9 in three patients, two patients each with del(13q), del(20q), and abnormalities of chromosome 1, and one patient each with del(3)(p13p21), dup(13)(q12q14), and del(11)(q21). At follow-up: Repeat cytogenetic studies while still in the chronic phase of the disease were performed in 19 patients at a median of 60 months (range, 8–198) from diagnosis. Of these, 4 had aquired new cytogenetic clones including 3 with normal cytogenetics at time of initial PV diagnosis. The new abnormalities included del(20q), del(5q), del(1p), chromosome 1 abnormality, and inv(3)(q21q26.2). At time of disease transformation: Leukemic transformation was documented in 3 patients of whom cytogenetic information at the time was available in 2 patients; both patients had normal results at time of initial PV diagnosis and complex cytogenetic abnormalities at time of leukemic transformation. In contrast, among 6 patients with available cytogenetic information at time of fibrotic transformation, the results were unchanged from those obtained at time of diagnosis in 5 patients. ii) Correlation between cytogenetics at diagnosis and JAK2V617F allele burden: Allele-specific, quantitative PCR analysis for JAK2V617F was performed in 71 patients using genomic DNA from archived bone marrow obtained at the time of the initial cytogenetic studies. JAK2V617F mutation was detected in 64 of the 71 (90%) patients; median mutant allele burden was 16% (range 3–80%) without significant difference among the different cytogenetic groups: normal vs. –Y vs. other cytogenetic abnormalities (p=0.72). iii) Clinical correlates and prognostic relevance of cytogenetic findings at diagnosis: Among several parameters studied for significant correlations with cytogenetic findings at diagnosis, an association was evident only for age (p=0.02); all –Y abnormalities (n=5) as well as 13 of the 15 (87%) other cytogenetic abnormalities occurred in patients ≥ 60 years of age. Stated another way, the incidence of abnormal cytogenetics (other than -Y) was 4% for patients younger than age 60 years and 15% otherwise. The presence of abnormal cytogenetics at diagnosis had no significant impact on either overall or leukemia-free survival. Conclusions: Abnormal cytogenetic findings at diagnosis are infrequent in PV, especially in patients below age 60 years. Furthermore, their clinical relevance is limited and there is not significant correlation with bone marrow JAK2V617F allele burden.

Abstract BACKGROUND : Leukemic transformation (LT) eventually occurs in 10–30% of patients with myelofibrosis with myeloid metaplasia (MMM). Hoever, there is limited data regarding bone marrow histological and cytogenetic changes that accompany the process. METHODS : The study population consisted of 67 consecutive patients with MMM in whom the diagnosis of LT was documented at our institution by bone marrow examination. Serial comparisons of both histological and cytogenetic changes were performed to monitor longitudinal changes accompanying disease progression. RESULTS : I. Bone marrow histologic changes during LT : All 67 patients displayed acute myeloid leukemia (AML) and all FAB subtypes except M3 were represented (most common were M7 at 25.4% and M0 at 22.4%). Median bone marrow myeloblast percentage was 43% (range 20–95) and cellularity 80% (range 5–95). However, only 37.5% and 30.3% had marked increases (> grade 2) in either reticulin fibrosis or osteosclerosis, respectively. Serial bone marrow comparisons (available in 33 patients at a median interval of 24.5 months (range; 2.1–110.4) after the diagnosis of MMM) demonstrated that LT was occasionally a focal process, but was always accompanied by a marked increase in myeloblasts. However, overall bone marrow cellularity changed by >15% in only 25% of the cases, none of the LT was associated with a > grade 1 change in reticulin fibrosis, and only 12% had an increase in osteosclerosis. On the other hand, LT was frequently associated with morphologic changes in megakaryocytes from large, round and clumped at the time of diagnosis of MMM to small, condensed and non-clumped at the time of LT. II. Karyotypic changes of MMM to LT: Karyotypic analysis was available in 32 patients (48%) at the time of MMM (abnormal in 63%) and 56 patients (84%) at the time of LT (abnormal in 91%). At LT the majority of patients (n=34; 60.7%) displayed poor risk karyotypes with either complex karyotypes or single abnormalities of adverse prognostic significance. In contrast, only two patients (3.6%) manifested prognostically favorable karyotypes with a translocation or inversion involving one of the core binding factors (t(8;21)(q22;q22);Inv(16)(q22)). Twenty-eight patients had chromosome analysis performed both at diagnosis of MMM and at LT. At diagnosis of MMM, 20 patients had either normal chromosomes or a single chromosome anomaly while only 7 displayed a complex karyotype with 3 or more chromosome anomalies. However, at LT all twenty-eight patients had abnormal karyotypes, including 17 patients with markedly complex karyotypes and only 9 with simple clonal anomalies. The recurrent numeric and structural anomalies observed at transformation to AML most frequently involved chromosomes 5, 6, 7, 8, 17, 19 and 21. Additionally, amongst the 26/28 (93%) of patients whose karyotype changed from MMM to LT 11 patients (43%) displayed evolution of an existing clone, and 15 (57%) developed one or more additional abnormal clones. CONCLUSIONS: The progression of MMM to LT is characterized by the emergence of new cytogenetic abnormalities as well as morphological changes in megakaryocytes. Unfortunately, the karyotypic profile that accompanies clonal evolution in MMM is often of the poor-risk category that undermines the value of aggressive chemotherapy in such patients. However, such therapy might be of value to the occasional patient with good-risk cytogenetic lesions.

AbstractInfant leukemias are a rare group of neoplasms that are clinically and biologically distinct from their pediatric and adult counterparts. Unlike leukemia in older children where survival rates are generally favorable, infants with leukemia have a 5‐year event‐free survival rate of <50%. The majority of infant leukemias are characterized by KMT2A (MLL) rearrangements (~70 to 80% in acute lymphoblastic leukemia), which appear to be drivers of early leukemogenesis. In this report, we describe three cases: a 9‐month‐old female infant with B‐acute lymphoblastic leukemia (B‐ALL), an 8‐month‐old female presenting with B/myeloid mixed phenotype acute leukemia (MPAL), and a 16‐month‐old male with B‐ALL. The first case had a normal karyotype and B‐ALL FISH results consistent with an atypical KMT2A rearrangement. The second case had trisomy 10 as the sole chromosomal abnormality and a normal KMT2A FISH result. Case 3 had trisomy 8 and a t(11;15)(q23;q21), an atypical KMT2A rearrangement by FISH studies, and a focal deletion of 15q with a breakpoint within the USP8 gene by chromosomal microarray. Mate pair sequencing was performed on all three cases and identified a KMT2A‐USP2 rearrangement (cases 1 and 2) or a KMT2A‐USP8 rearrangement (case 3). These recently characterized KMT2A fusions have been described exclusively in infant and pediatric leukemia cases where the incidence varies vary according to leukemia subtype, are considered high‐risk, with a high incidence of central nervous system involvement, poor response to initial prednisone treatment, and poor event free survival. Additionally, approximately half of cases are unable to be resolved using standard cytogenetic approaches and are likely under recognized. Therefore, targeted molecular approaches are suggested in genetically unresolved infant leukemia cases to characterize these prognostically relevant clones.

6614 Background: CDKN2A locus on chromosome 9p21 is implicated in altered molecular pathways leading to leukemogenesis as a tumor suppressor by inhibiting the proliferative kinases CDK4/CDK6 and blocking the cell-cycle division during G1/S phase. Deletion of CDKN2A locus is frequently seen in ALL, although prognostic significance remains unclear. Methods: Retrospective chart review at Mayo Clinic between 8/2005-11/2011 was performed on adult B-ALL patients (pts) who underwent fluorescent in situ hybridization (FISH) studies at diagnosis. Survival estimate was calculated using Kaplan-Meier statistics. Event-free survival (EFS) was defined as time between diagnosis and induction failure, relapse, or death, while overall survival (OS) as time between diagnosis and death Results: Out of 27 pts who had FISH studies for CDKN2A, 15 (56%) pts had CDKN2A deletions (8 homozygous/7 hemizygous), while 12 (44%) pts had diploid cytogenetics (none had abnormalities of MLL, bcr/abl fusion or CDKN2A deletion on FISH). There was no significant difference in median age, gender, WBC, hemoglobin, platelet count, LDH or complete remission (CR) rate (p=0.924) between the two groups. CDKN2A-deleted pts had higher circulating blasts (34% vs 16%, p=0.017). Of 13 CDKN2A-deleted pts, chromosome 9p was intact in 9 (69%) pts using routine cytogenetics. In the CDKN2A-deleted group, allogeneic stem cell transplant (ASCT) was performed in 7 (47%) pts at first CR and 1 at second CR. Four of 15 (27%) CDKN2A-deleted pts also had bcr/abl fusion. Five-year EFS was poorer in CDKN2A-deleted pts compared to normal FISH group (22% vs 60%, p=0.042), while 5-year OS was 72% vs 60% (p=0.308), respectively. Excluding the 4 bcr/abl fusion pts, 5-year EFS was still statistically significant (p=0.008). In the CDKN2A deleted group, both 5-yr EFS (80% vs 0%, p=0.006) and OS (100% vs 42%, p=0.016) were significantly superior in pts who received ASCT. Conclusions: CDKN2A deletions predict earlier relapse in pts with B-ALL. Majority of 9p abnormalities were only found by FISH testing and missed by conventional cytogenetics. In CDKN2A deleted pts, ASCT gave overall survival advantage. Further investigation through larger cohorts of pts is needed to validate these findings.

7047 Background: In addition to secondary AML (sAML), important lifestyle and environmental exposures associated with increased risk of AML development have been identified in recent case-control studies including obesity (BMI>30kg/m2), smoking, regular acetaminophen use, and rural/farm habitat. The association of these exposures with AML cytogenetic risk groups is unknown. We therefore evaluated relevant exposures in a cohort of 301 AML patients with confirmed central cytogenetics analysis diagnosed and treated at Mayo Clinic FL and AZ since 1995. Methods: Documented patient exposures were extracted from central electronic medical records, including: prior chemotherapy/radiation or hematologic malignancy, occupation, select medications, “toxins” (esp. benzene) and solid organ transplantation (SOT). Standard cytogenetic risk categories (including intermediate abnormal) were applied. The association of epidemiologic exposures with cytogenetic risk was evaluated on multivariable analysis using logistic regression models. Results: sAML was significantly associated with cytogenetic risk groups, as was prior SOT, healthcare occupation, farm habitat and toxin exposures [see Odds Ratios (OR), Table). In contrast, prior radiation for epithelial malignancies, smoking and BMI were not independently associated with specific cytogenetic risk categories. Conclusions: Specific epidemiologic exposures are significantly associated with AML cytogenetic risk categories suggesting a unique clinical phenotype. This supports a link to leukemogenesis and requires validation in a controlled prospective therapeutic study. [Table: see text]

8116 Background: POEMS syndrome, or osteosclerotic myeloma, is an uncommon plasma cell disorder associated with Peripheral neuropathy, Organomegaly, Endocrinopathy, M protein, and Skin changes, as well as bone lesions, Castlemans disease, and edema. The pathogenesis of POEMS is poorly understood, and its clinical course is distinct from Multiple Myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS). While various cytogenetic abnormalities have been well described in MM and MGUS, we provide the first report of testing for these abnormalities in POEMS syndrome. Methods: Using a prospectively held dysproteinemia database, we reviewed all cases of POEMS seen at our institution, identifying 36 with metaphase cytogenetic testing results, and 9 with fluorescence in situ hybridization (FISH) testing results. Combined cytoplasmic immunoglobulin/FISH testing (cIg- FISH) was performed with fluorescent-tagged antibodies to kappa/lambda immunoglobulin and FISH probes corresponding to the following anomalies: trisomies 3, 7, 9, 11, 15 and 17; del13/del13q; 14q32 split/del14; and t(11;14). Results: Five patients had insufficient plasma cells for cIg-FISH, and 9 were adequate for testing. Monosomy 13 was seen in 5 of the 9 cIg-FISH samples of which 2 of these cases also had apparent monosomy 14. cIg-FISH in one patient revealed trisomy 3 and 7. No abnormalities were seen at 11q13 (CCND1), 17p13 (p53) or translocations involving 14q32 (IGH). Thrity-eight total karyotypes analyses were attempted, though two showed an insufficient number of suitable metaphases. Of the 36 karyotype analyses, 31 were normal, 2 displayed characteristic plasma cell anomalies (hyperdiploid with structural anomalies), 2 treated patients displayed del20q anomalies and 1 patient had a constitutional 13;14 translocation. Conclusion: We are the first to report del13 as a possibly common abnormality in POEMS syndrome, detected by cIg-FISH in 5 of 9 (55%) samples with sufficient plasma cells, similar to the rate observed in MM and MGUS. The lack of abnormalities at 14q32 (IgH locus) is in contrast to MM and MGUS. Abnormal karyotypes, consistent with dividing plasma cells, are rare in POEMS, observed in only 2 of 36 (5.5%) cases. These observations could possibly lend insight into all three disorders. No significant financial relationships to disclose.

7077 Background: MDS includes a heterogenous group of hematopoietic stem cell malignancies characterized by ineffective hematopoiesis and recurring clonal cytogenetic abnormalities with poorly understood functional consequences. Interstitial deletion of chromosome 5 including band q31 is of special interest currently because of the striking effectiveness of lenalidomide therapy in patients with this lesion. Methods: We reviewed the clinical and pathological features of 175 consecutive patients with 5q31 deletions whose final diagnosis was MDS from 1996 to 2006. Patients not meeting the definition of a clonal chromosomal anomaly (i.e., only 1 abnormal metaphase) and those with >20% marrow blasts (now defined as AML) were excluded. Results: The median age at diagnosis was 73 years old (range 8–91). The 5 most common MDS subtypes (WHO classification) were RAEB2 (38 cases), 5q- syndrome (33 cases), MDS NOS (26 cases), RCMD (22 cases), and RAEB1 (20 cases). Chromosomal breakpoints encountered most frequently were q13q33 (86 cases), q15q33 (38 cases), and q22q33 (14 cases). The 5q deletion was present as a sole cytogenetic anomaly in 31%, was present along with one other anomaly in 10%, and was part of complex karyotype in 59%. Median time to death from confirmation of diagnosis at our institution was only 7.2 months (range 1 month –1.8 years). Survival was greatest in those diagnosed with 5q- syndrome, but the median survival time of 1.8 years (p=0.001) was lower than reported in other series. Survival was also superior in women (7.9 months, versus 6.6 months for men, p=0.05) and those with non-complex cytogenetics (1.44 versus 0.41 years, p<0.001). Poorer survival was noted in those with prior chemotherapy (median 6.6 months versus 7.6 months, p=0.01). Differences in breakpoint (p=0.55) and number of metaphases involved with the 5q abnormality (p=0.08) did not have a statistically significant impact on survival. Conclusion: Classic 5q- syndrome as defined by the WHO represents only a minority of MDS patients with interstitial 5q deletions. Although the short survival in our series compared with previous reports may be due in part to referral bias, it is also possible that deletions of chromosome 5q are less benign than previously suspected. No significant financial relationships to disclose.