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Background Emergency Medicine Telehealth (TeleEM) represents an opportunity to work directly with referral centres, rural facilities and underserved areas to mitigate unnecessary testing, optimise resource utilisation and facilitate patient transfers across health systems. To optimise the impact of a TeleEM programme, a tool is needed to remotely monitor patient activity in multiple emergency department facilities, concurrently. Methods After identifying data sources for activation criteria put forth by the TeleEM operations group, rules were constructed within the electronic health record to facilitate data checks and ultimately produce a yes/no response if the category’s conditions were met. Responses were organised into a table, with functionality allowing end users to drill into the different sites to see patient-specific information for patients meeting activation criteria. Conclusions The TeleEM dashboard allows for proactive engagement by the TeleEM physician and strengthens the team-based approach of critically ill.

Lipid droplets (LDs) are fat‐storage organelles that play critical roles in energy homeostasis, but can excessively accumulate in metabolic diseases such as obesity and fatty liver where hepatocytes become grossly engorged with excess lipid. The catabolism of LDs aids in disease resolution and occurs in part by lipophagy, a form of selective autophagy, but the molecular and vesicle trafficking events that facilitate this process are not fully understood. During lipophagy, autophagosomes are thought to target LDs prior to fusion with acidic lysosomes, where neutral lipids are terminally degraded by lysosomal acid lipase. Ultrastructural viewing of hepatocytes showing LDs contained within electron‐dense acidic vesicles is consistent with this concept. In addition to canonical autophagy, we find that most LDs undergoing degradation are encased within single‐membrane endo‐lysosomes, and few LDs are observed within traditional double‐membrane autophagosomes. Further, studies of LD catabolism in yeast have shown that LDs can be directly internalized by the large acidic vacuole through a process known as microlipophagy. Thus, the GOAL of this study was to test if similar microlipophagy mechanisms occur in mammalian cells such as hepatocytes, and whether this process involves autophagy. METHODS To test this, we used microscopic fatty acid tracing studies and time‐lapse confocal microscopy to determine the role of autophagosomes versus endo‐lysosomes in LD catabolism. To trace the fate of LDs into terminal degradative vesicles, cells were first loaded with the fluorescent lipid marker Bodipy C12, then treated for 24h with LAListat, an inhibitor of lysosomal acid lipase. RESULTS We observed a ~5‐fold higher incidence of LDs within endo‐lysosomes (marked with the tetraspanin CD63), compared with autophagosomes (marked by the autophagy protein LC3). Furthermore, siRNA knockdown of macroautophagy proteins (Atg5, Atg7, and Fip200) did not inhibit LD internalization by endo‐lysosomes, suggesting that autophagy is not a prerequisite for this process. In addition, time‐lapse microscopy revealed a direct internalization of cytosolic LDs by endo‐lysosomes positive for lysotracker or CD63‐mCherry. CONCLUSION These findings suggest that hepatocytes utilize a distinct form of microautophagy that entails the direct envelopment of cytoplasmic LDs by endocytic vesicles such as multivesicular bodies and lysosomes/late endosomes. In addition to lipolysis and canonical macroautophagy, this process plays an important role in the catabolic utilization of LDs by the hepatocyte. Support or Funding Information This study was supported by NIH R01DK044650 (to M.A.M.), RO1AA020735 (to M.A.M.), and the K99AA020735 (to M.B.S.).

Hepatocellular Carcinoma (HCC) is a highly fatal liver cancer with no effective treatments. HCC tumors, formed after long‐term viral or alcohol related inflammation and cirrhosis, have a surprisingly low number of genetic mutations. Prior research has found that epigenetic patterns, such as DNA methylation at gene promoter sites, are common in HCC patients. Recent improvements in genetic sequencing and online genetic databases, have allowed us to identify a set of gene targets, including FMO3, for HCC detection or treatment. The hypothesis is that FMO3 is reduced by epigenetic dysregulation, leading to tumor formation. To find the connection between FMO3, epigenetic events and HCC tumor pathways, our lab created novel HCV‐stable and non‐infected HCC cell lines. We also used Huh7 and Huh7.5 cells to show the epigenetic changes in stressed cells and methylation inhibited cells. To mimic inflammation and stress leading to epigenetic changes, Huh7 cells were exposed to heat shock at 40°C for 40 min. Huh7.5 cells were treated with epigenetic inhibitor 5‐Aza‐2 deoxycytidine. RT‐qPCR and Western Blot show that FMO3 is significantly reduced in stressed cells and upregulated when treated with the methylation inhibitor. These results indicate that FMO3 may be used for early cancer risk detection and/or to improve treatment options by identifying the relationship between epigenetic regulation and tumorigenesis. Support or Funding Information NIH NIDDK 1R01DK110024‐01A1

Abstract Background: Chronic myeloid leukemia (CML) is invariably associated with the reciprocal translocation of BCR and ABL to form the Philadelphia chromosome (Ph), t(9;22)(q34;q11). At diagnosis, a small proportion of patients display additional cytogenetic abnormalities and/or a variable proportion of cytogenetically normal metaphases that coexist with Ph-positive metaphases. The objective of the current study was to examine the prognostic relevance of these two scenarios. Methods: The study population consisted of 65 (47.7% female) consecutive, newly diagnosed CML patients seen at the Mayo Clinic with a median age of 59 years. 44.5 percent were initially treated with interferon alpha (IFN) resulting in complete cytogenetic remission in 10.7 percent for a median length of 5.83 years, partial cytogenetic remission in 3.57 percent for a median length of 2 years. 55.5 percent were treated with imatinib (Gleevec) resulting in complete cytogenetic remission in 54.1 percent for a median length of 3.08 years, partial cytogenetic remission in 13.5% for a median length of 1.08 years. Results: Survival at five years through Kaplan-Meier analysis was approximately 92 percent in patients demonstrating only the Ph chromosome (n = 53), versus 60 percent in patients with additional chromosomal abnormalities (n = 12; p < 0.0001 by both Logrank and Breslow-Gehan-Wilcox analysis). Furthermore, patients with additional chromosomal abnormalities demonstrated lower rates of either complete or partial cytogenetic remission with imatinib therapy. Similarly, five year survival of patients with less than 90% Ph-positive metaphases at diagnosis (n = 4) was approximately 60% compared to 92% in patients with greater than 90% Ph-positive metaphases (n = 61; p = 0.01 by Logrank and p = 0.001 by Breslow-Gehan-Wilcox analysis). Additionally, the former group of patients was significantly less responsive to imatinib. Finally, there was significant correlation between Ph-positive metaphase mosaicism and the presence of additional chromosomal abnormalities (p = 0.05). Conclusion: Although it is tempting to speculate the possibility that Ph-chromosome mosaicism and/or additional cytogenetic abnormalities at presentation of CML is a surrogate for the presence of Ph-negative imatinib-resistant clones, the preliminary results from the current study require validation from a larger study. Figure Figure Figure Figure

Abstract E1496 is a phase III trial designed to evaluate the ability of 2 years (yr) of maintenance rituximab (MR) to prolong progression-free survival (PFS) after CVP (cyclophosphamide 1 G/m2 day [d] 1, vincristine 1.4 mg/m2 [max = 2 mg] d 1, prednisone 100 mg/m2 d 1–5) chemotherapy in stage III–IV follicular grade 1 and 2 and small lymphocytic lymphoma. After CVP treatment to maximum response, (6–8 cycles), stable and responding patients (pt) were randomized to MR (375 mg/m2 weekly x 4) every 6 months x 4 or observation (OBS). Stratification factors included histology, response and residual disease after CVP. With 3-yr median follow-up, survivals (from time of randomization, one-sided logrank p values) for all pt (n=304) favored MR for PFS (p = 3 x 10–8; hazard rate {HR} = 0.38 [0.28;0.54, 95% confidence intervals]) and OS (p = 0.09; HR = 0.66 [0.36–1.22]). Because the large majority of pt have FL and because rituximab efficacy is notably greater in FL, we focused in this report on the 237 FL pt. Median age was 58 yr, 65% were stage IV, 64% had marrow disease, 64% had high tumor burden and 37% had high-risk disease by the follicular lymphoma prognostic index. PFS after randomization was significantly longer for MR vs OBS (p = 3 x 10-7; HR = 0.39 [0.27;0.57]). The estimated PFS at 4 yr (~4.5 yr after start of treatment) was 56% for MR vs 33% for OBS. Differences in PFS were significant within the predefined strata and the differences were most significant in favor of MR for pt with high initial tumor burden and minimal residual disease after CVP. Overall survival was superior for MR (p = 0.03; HR = 0.51 [0.25;1.04]. Estimated OS at 4 yr (~4.5 years after start of treatment) was 88% for MR vs 72% for OBS. Of 33 deaths, 21 occurred on the OBS arm. These data demonstrate that maintenance rituximab not only significantly delays disease progression in FL compared with OBS but that a substantial proportion of patients treated with MR remain disease-free at 4 years after the completion of CVP. These are the first data to strongly suggest a survival benefit with a therapy that includes rituximab and CVP and the first to strongly suggest a survival benefit with maintenance rituximab in FL.

Abstract Deletion 5q in Acute Myeloid Leukemia (AML): a Clinicopathological Description of 79 Cases From a Single Institution Rafael Santana-Davila, Shernan G. Holtan, Rhett P. Ketterling, Ryan A. Knudson, David P. Steensma, Dong Chen, James D. Hoyer, Curtis A. Hanson, Ayalew Tefferi. Background: Deletion 5q (del(5q)) is a lenalidomide-sensitive cytogenetic abnormality commonly seen in patients with myeloid disorders. In this study we analyze the clinicopathological characteristics of patients with AML and del(5q). Methods: Patients with del(5q) and AML were identified through a database query of our institutional cytogenetic database from May, 1992 through December, 2005. Both peripheral blood and bone marrow specimens from each patient were morphologically examined by a hematopathologist (DC, JDH and/or CAH). A morphologic diagnosis was given based on current WHO criteria. A critical review of the patient history was performed for each patient. Results: A total 79 patients were identified. Median age was 71 (range 39–87) years, 56% (n=43)were female. The most common subtype according to the FAB classification was M2 (n=23, 29%). In 35 (44%) patients AML developed a median of 9.4 (range 1–294) months since the diagnosis of a pre-existing myeloid malignancy, of which myelodysplastic syndrome accounted for 24 (9 cases of MDS NOS, 6 of RA, 6 of RAEB1, 2 of RAEB-2, and a single RARS), a myeloproliferative neoplasm in 10 (4 cases of a CMPD NOS, 4 cases of PV and a single case of ET and PMF each) and 1 case of a prior history of AML with a t(8;21). The del(5q) was documented in 7 of this 24 patients in the antecedent hematologic disorder. Neither a history of prior exposure to cytotoxic agents nor a prior myeloid disorder was found in 44% (n=35) of the patients. Del(5q) was commonly associated with a complex karyotype (n=67), however in 9 patients it was found to be the sole abnormality. The most frequent breakpoint was q13q33 (n=47) followed by q15q33 (n=12). Initial pathological description did not identify any morphological abnormalities in 6 cases, in contrast myelodysplasia involving at least two cell lines was appreciated in 58% (n=46) of the patients. The median survival was 2.8 months. The majority of the subjects (n=51, 65%) received palliative treatment, 7 patients were lost to follow up and no treatment information was available for review and the remaining 21 received induction chemotherapy with a curative intent, in this group median survival was 8.8 months with 52% (n=11) of patients achieving a complete response. Surprisingly the only factor that appeared to alter survival in the whole group was the presence of the breakpoint in chromosome 5 being distal to q15 (median 2.8 vs 4.1 months, p=0.025) Conclusions: This study constitutes the largest review of del(5q) in AML, its presence is currently associated with advanced age and a poor survival. Close to half of the patients in our series were classified as de novo AML. Although more commonly encountered as part of a complex karyotype it can also be present as a single abnormality. The different cytogenetic characteristics of the del(5q) may impact survival and this deserves further investigation. Figure. Survival of patients with AML and del(5q) in which the breakpoint was found to be distal to q15 (straight line) compared with patients in which the breakpoint was proximal to q13 (dotted line). Figure. Survival of patients with AML and del(5q) in which the breakpoint was found to be distal to q15 (straight line) compared with patients in which the breakpoint was proximal to q13 (dotted line).

Abstract The tumor microenvironment in B-cell non-Hodgkin’s lymphoma (NHL) plays an important role in supporting the growth and survival of malignant lymphocytes. In contrast, the extent to which this is true in T-cell NHL is less clear. While professional monocytederived antigen-presenting cells (MDC) are required for T-cell activation and survival, a growing body of evidence demonstrates that MDC may promote the survival of malignant T cells. Immunohistochemical staining of skin biopsies from cutaneous T-cell lymphoma (CTCL) patients (n=11) demonstrated a rich infiltrate of CD68+ macrophages and CD1a+ dendritic cells (DC). As these cells are derived from CD14+ monocytes, we examined the role of monocytes in promoting survival in malignant T cells obtained from CTCL patients (n=9). Initially, peripheral blood mononuclear cells (PBMC) were either depleted of CD14+ monocytes (>85% depleted) or mock-depleted prior to being cultured. Viability of malignant CD4+CD7− T cells was determined by Annexin V/7-AAD staining. While 90.9% (S.D. +/− 0.4%) of mock-depleted malignant T cells were viable, only 73.9% (S.D. +/− 1.3%) of monocyte-depleted cells remained viable, suggesting that monocytes may promote the survival of malignant T cells. In a similar fashion, HuT-78 cells (Sézary Syndrome cell line) were cocultured with CD14+ monocytes from normal donors. Compared with HuT-78 cells alone, the presence of CD14+ monocytes resulted in a 2.7 fold increase in thymidine incorporation (n=5; S.D. +/− 0.6). This is largely due to cytokine production, as the same experiment performed with a transwell insert resulted in a 2.1 fold increase in HuT-78 thymidine incorporation (n=5; S.D. +/− 0.4). Similar results were obtained using additional Sézary Syndrome (i.e. SeAx) and Mycosis Fungoides (i.e. MyLa) cell lines. Monocytes obtained from normal donors were subsequently cultured and cell-free conditioned media was obtained 48 hours later. Media supplemented with monocyte-conditioned media (monocyte-CM) prevented the induction of apoptosis in CTCL cell lines as measured by thymidine incorporation, trypan blue exclusion and Annexin V/propidium iodide staining. This affect was monocyte-specific, as neither T-cell nor B-cell conditioned media were observed to promote survival of CTCL cell lines. Furthermore, monocyte-CM had no affect on resting or anti-CD3 activated normal T cells. We next cultured malignant T cells obtained from PBMC (n=6) or skin biopsies (n=3) from CTCL patients in the presence or absence of monocyte-CM and assessed cell viability by Annexin V staining. 32.1% (S.D. +/− 14.7%) and 60.5% (S.D. +/− 21.5%) of malignant T cells isolated from PBMC remained viable in the absence or presence of monocyte-CM, respectively; 13.0% (S.D. +/− 10.8%) of malignant T cells isolated from skin biopsies remained viable, compared with 26.5% (S.D. +/− 8.2%) of cells grown in the presence of monocyte-CM (p=.03). Given the prevalence of MDC within CTCL-involved skin and their potential role in promoting the survival of malignant T cells, one may predict that malignant T cells may recruit monocytes in a chemokinedependent fashion. Therefore, cell-free conditioned media from CTCL cell lines (HuT- 78, SeAx, MyLa) was collected and used to promote monocyte chemotaxis in a standard chemotaxis assay. Only neutralization of CCL5 (RANTES) was capable of abrogating monocyte chemotaxis, demonstrating that the production of CCL5 by malignant T cells promotes monocyte migration. Therefore, we examined serum CCL5 levels by ELISA from both normal donors (n=24) and CTCL patients (n=23) and found an approximately 3-fold elevation in serum CCL5 in CTCL patients (normal donors: mean CCL5 10.0 ng/mL; 95% CI 7.1–13.0; CTCL patients: mean 29.2 ng/mL; 95% CI 20.6–37.8; p<0.0001). Serial serum samples were available for 6 patients, 4 of whom had progressive disease. Serum CCL5 increased from a mean of 17.9 ng/mL before progression (S.D. +/− 7.0) to 44.8 ng/mL (S.D. +/− 20.0) after progression (p=.04). In contrast, serum CCL5 decreased by at least 50% in both patients with responsive disease. Our findings demonstrate that monocytes, recruited by malignant T cells in a CCL5-dependent fashion, promote the survival of lymphoma cells in CTCL, thus raising the possibility that targeting tumor-associated monocytes and MDC may represent a novel therapeutic strategy in CTCL.

Abstract Malignant plasma cell (PC) disorders are clonal diseases based on their immunoglobulin variable region sequence signature. However, intratumor phenotypic, genetic, and morphologic heterogeneity is often observed, fueling the notion that a subpopulation of the malignant PC clone may have extensive self-renewal properties whereas others may not. Little information exists regarding the relationship between these putative tumor subpopulations that is instrumental to our understanding of the growth, progression and therapeutic targeting of PC disorders. We recently described establishment of two novel cell lines from one patient initially diagnosed with primary amyloidosis (ALMC-1), who eventually progressed to a combination of AL and symptomatic multiple myeloma (MM; ALMC-2). Although both cell lines are clonally related, they exhibit a number of intriguing differences, including a marked variability in their makeup of mononuclear (MoN) and multinuclear cells (2 − >10 nuclei; MuN). The ALMC-1 cell line consistently displays a much larger fraction of MuN cells (~50%) than the ALMC-2 cell line (~20%). By contrast, the growth rate of the ALMC-2 cells is significantly higher than ALMC-1 cells suggesting an inverse relationship between growth rate and fraction of MuN cells. It has been demonstrated that MoN plasmablastic morphology is a predictor of poor survival in MM, however the clinical significance of MuN PCs, which are frequently observed in bone marrow biopsies, has yet to be determined. We therefore used the ALMC-1 and ALMC-2 cell lines to begin to test the hypothesis that the MoN fraction in both cell lines contains cells with extensive self-renewal properties whereas the MuN cells are no longer capable of cell division. The central questions become by what mechanism are MuN PCs generated and how are MoN PCs maintained? Two hypotheses that can explain the dual persistence of both types of cells are: random cell fusion; regulated or sporadic cell division of MoN cells into 2 daughter cells, one of which divides normally and the other one fails to undergo cytokinesis. To address the first possibility, each cell line was transfected with GFP or YFP. Single positive (GFP or YFP) cells were then mixed and cocultured for assessing the frequency of dual positive cells by flow cytometry at various time points. However, studies to date suggest this mechanism does not occur. To begin to address the second possibility and determine whether extrinsic factors, e.g., cytokines, may regulate the rate of generation of MuN PCs, we cultured both cell lines +/− IL-6 and IGF-I and assessed numbers of MoN and MuN PCs. Initial analyses suggest that IL-6, but not IGF-I, increases the proportion of MoN PCs in both cell lines. To address the hypothesis that MuN PCs are no longer capable of growth, cells were labeled with bromodeoxyuridine (BrDU) to assess the capability of MuN cells to synthesize DNA. We observed that MuN PCs incorporating BrDU did so uniformly in each nucleus present in the cell. We then assessed the ability of cell division of MuN cells by quantitating normal vs abnormal metaphases in both cell lines and observed that >90% of metaphases were present in MoN PCs, suggesting that MoN PCs largely give rise to MuN PCs and the latter are likely compromised in cytokinesis. As centrosomes play a critical role in regulating cell division and centrosome abnormalities have been noted in MM by others, we next used gamma-tubulin immunofluorescence to detect centrosomes. MoN PCs exhibited uniformly normal centrosome numbers and positioning while MuN PCs showed clear centrosomal abnormalities including accumulation of centrosomes, centrosome clustering, and multiple directional centrosome polarization, suggesting a mechanism by which the MuN cells may be generated. In summary, our data suggest that MuN PCs lack growth potential and that intrinsic and/or extrinsic factors may drive accumulation of these cells. These observations support the possibility that patients with a larger proportion of MuN PCs may have differences in clinical outcome from those patients with largely MoN PCs. To test this, we have begun hematopathological analysis of a large series of patients diagnosed with various plasma cell disorders. Knowledge of the signals that regulate the balance between MoN and MuN cells could lend itself toward identification of therapeutic modalities that may maximize differentiation of tumor cells into end-stage cells.

Abstract Background: For most patients with MDS, the disease-associated molecular abnormalities are unknown, which contributes to diagnostic uncertainty and has limited development of effective therapies. Chromosomal deletions such as del(5q) or monosomy 7 are more common than translocations in MDS, but balanced translocations are more likely to be pathobiologically informative. Here we report cloning of an MDS-associated translocation that revealed a novel recurrent molecular abnormality. Methods: We first studied a 71-year old man who presented with MDS and t(6;9)(p21.3;q34) as an isolated chromosomal abnormality in 18 of 20 metaphases. FISH assays for DEK/CAN and ABL rearrangements were unrevealing. We generated somatic hybrid murine/human cell lines from a buffy coat; microdissected and amplified derivative chromosomes; and hybridized to 6p/9q custom comparative genomic hybridization (CGH) arrays. The CGH results considerably narrowed the 6p and 9q breakpoints, which were then amplified by long-range PCR and sequenced to define the rearrangement. Results: The IER3 gene (Immediate Early Response 3; also known as IEX-1) at 6p21.3 was found to be separated from its upstream regulatory elements in this rearrangement and translocated to a transcript-poor region of 9q. RT-PCR confirmed marked downregulation of IER3 expression in the patient compared to healthy controls. IER3 is a plausible candidate for involvement in MDS because of its known role in regulating death receptor-induced apoptosis, interaction with NF-κb pathways, and its importance in response to genotoxic stresses such as ionizing irradiation. We then identified archival bone marrow cell pellets from 204 additional patients with various clonal hematological disorders and chromosomal rearrangements involving 6p21 or 6p22 (i.e., translocations, inversions, deletions, or additions), and designed a splitsignal FISH probe set to assay IER3. FISH results were abnormal in 8 additional patients (9/205 pts total abnormal, 4.4%): 3 split signals and 6 amplifications (one patient had both abnormalities); all 8 patients had MDS and 6p rearrangements as part of a more complex karyotype. FISH studies in MDS patients without 6p rearrangements are ongoing. RTPCR in MDS patients without 6p rearrangements demonstrated down-regulation of IER3 by >2-fold in 38% of patients (67% lower-risk) and up-regulation in 12% of patients (50% higher-risk) when compared to the mean for healthy controls. Direct sequencing of the IER3 coding region and the promoter region in 30 patients without 6p rearrangements revealed no point mutations, but the prevalence of non-synonymous single nucleotide polymorphism rs3094124 (p.A127P) was higher than expected in patients (variant in 28.3 % of MDS alleles vs. 8.6% of 116 HAP-CEU controls, p=0.0015). IER3−/− mice are known to have hypertension, cardiac hypertrophy, and epithelial proliferation, but are not anemic (Sommer SL et al J Appl Physiol 2006). We performed methylcellulose hematopoietic colony growth assays using bone marrow mononuclear cells from IER3−/− mice and wildtype controls, and noted no differences in BFU-E, CFU-E, and CFU-GM growth under unstressed conditions. Studies of IER3 expression induction under stressed conditions in primary MDS cells are ongoing. Conclusion: IER3 rearrangements represent a novel clonally-restricted recurrent genetic abnormality in MDS. Dysregulation of IER3 expression is common in MDS, even in patients without 6p rearrangements. This is the first time IER3 has been linked to human disease. Clarification of the role of IER3 in MDS is likely to yield new insights into MDS pathobiology.

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.