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Background: The term classical hematology (CH), referring to a subspecialty focusing on non-cancer blood disorders, was officially adopted by the American Society of Hematology (ASH) in 2022. There is a perceived shortage of classical hematologists, although data are limited (Winter JN, Hematologist 2022). Prior studies have shown that <6% of hematology-oncology fellows pursue a practice subspecializing in CH after training (Todd RF, Blood 2004; Marshall Al, Blood Adv 2018). Moreover, mentorship is consistently cited as the most important factor guiding fellows' career decisions (Sharma D, Blood Adv 2019; Masselink LE, Blood Adv 2019). To help bridge the CH workforce gap, ASH has supported additional hematology-focused fellowship programs (HFFP) within select hematology-oncology fellowship programs. CH constitutes a large proportion of consults in US National Cancer Institute (NCI)-designated cancer centers (West CV, JCO Oncol Pract 2024). The goals of our study were: 1) to determine the proportion of adult hematologist-oncologists within NCI cancer centers who practice CH; and 2) to describe the physician characteristics of cancer centers with HFFP and compare these centers to those without HFFP. Methods: We included all NCI-designated cancer centers with a clinical program as of April 1, 2024. The only exception was St Jude Children's Hospital due to its pediatric focus. We obtained the practice profile of each internal medicine-trained adult hematologist-oncologist (henceforth, physician) as well as the availability of HFFP from the respective cancer center websites. We also searched the corresponding department of medicine and division of hematology at each affiliated academic institution to ensure inclusion of all physicians practicing CH. Each physician was classified into one of the following categories: classical hematologist (attending to only non-cancer conditions), general hematologist-oncologist (cancer and non-cancer conditions), and oncologist (cancer only). The number of hematology-oncology fellowship programs in the US was obtained from the Accreditation Council for Graduate Medical Education. Results: We included 64 NCI-designated cancer centers, 55 of which were considered as comprehensive cancer centers. There was a total of 4,616 physicians (3,891 oncologists [84.3%], 487 hematologists-oncologists [10.6%], and 238 classical hematologists [5.1%]). The median numbers of physicians, oncologists, general hematologist-oncologists, and classical hematologists per center were 55 (range, 16-275), 45 (range, 12-270), 5 (range, 0-48), and 3 (range, 0-13), respectively. The median proportions of classical hematologists and physicians practicing CH (general hematologist-oncologists plus classical hematologists) were 5.1% (range, 0-20.0) and 14.9% (range, 0-55.6%), respectively. There were 12 HFFP within NCI-designated cancer centers (18.8%). Most (11/12) centers with HFFP had >50 physicians (median 95 [range, 38-185]) and >5% classical hematologists (median 6% [range, 3.8-13.5%]); 11 centers with similar characteristics did not have HFFP. Centers with HFFP have significantly higher numbers of physicians (median 95.0 [range, 38-185] vs 49.5 [range, 16-275]; P=0.001) and classical hematologists (median 6.0 [range, 3-13] vs 2.0 [range, 0-11]; P<0.001) but similar proportions of classical hematologists (median 6.0% [range, 3.8-13.5] vs 4.5% [range, 0-20.0]; P=0.078) and physicians practicing CH (median 12.3% [range, 6.5-47.7] vs 15.7% [range, 0-55.6]; P=0.402) compared to those without HFFP. Conclusions: Among adult hematologist-oncologists at NCI-designated cancer centers, only 1 in 20 are classical hematologists, although 1 in 7 have CH as part of their practice. Within NCI-designated cancer centers, only 1 in 5 have an HFFP. These findings suggest that there is an opportunity for NCI-designated cancer centers to encourage and recruit physicians subspecializing in CH and a rationale to create additional HFFPs. These measures may help further alleviate CH workforce shortages and expand CH mentorship to meet the needs of an increasingly complex subspecialty within hematology.

Background: Erdheim-Chester disease (ECD) manifests as multi-organ infiltration of clonal histiocytes with mutations primarily in the mitogen-activated protein kinase (MAPK) pathway. The revised classification of histiocytosis (2016) categorizes ECD with typical bilateral, symmetric osteosclerosis of the lower extremity long bones as classical (C) and as non-classical (NC) if otherwise. The clinical and biological significance of this classification is unclear. This study compared the clinical and genotypic findings of the 2 subtypes within a large cohort of ECD patients. Methods: We included patients seen at our institution since 1990 meeting the following criteria: A) had an ECD diagnosis based on the revised criteria by Haroche J, et al. (Blood 2020;135:1311-1318); B) completed whole-body imaging studies including long bones of the legs. Classification as C-ECD required symmetric osteosclerosis of the distal femur and/or proximal tibia/fibula. Results: A total of 145 patients were enrolled, comprising a male-to-female ratio of 2:1 (66.2% male). C-ECD was diagnosed in 77.2% of cases, and NC-ECD in 22.8%. The median age at diagnosis was similar with 58.5 years (range, 18-82) in C-ECD and 55 years (range, 20-81) in NC-ECD, (p=0.65). The most frequently affected systems included skeletal (81.4%), renal (60.0%), vascular (45.5%), cardiac (40.0%), central nervous (38.6%), sinus (37.2%), pulmonary (36.6%), and adrenal (32.4%). The numbers of organs involved were significantly higher in C-ECD compared to NC-ECD (median 5 vs 3, p<0.01). Higher rates of skeletal (100% vs. 18.2%, p<0.01), adrenal gland (37.5% vs. 15.2%, p=0.02), and sinus (44.6% vs. 12.1%, p<0.01) involvement were observed in C-ECD. Arginine vasopressin deficiency (AVP-D) was exclusively observed in C-ECD (20.7% vs. 0%, p<0.01). NC-ECD had a higher rate of cardiac involvement (69.7% vs. 31.3%, p<0.01). No significant differences were found in other systems. The overall median time between onset of the first symptoms/signs to diagnosis was 15 months with no significant difference between C-ECD and NC-ECD (17.5 vs. 12 months, p=0.18). The median time to diagnosis of ECD in patients with AVP-D was 38.5 months, compared to 12 months without AVP-D (p=0.09). Genetic testing was conducted in 86.2% of patients and B-Raf proto-oncogene (BRAF) alterations were identified in 59.2% of the tested cases. BRAFV600E was more prevalent in C-ECD (61.3% vs. 21.9%, p<0.01), whereas non-V600 mutations were more commonly found in NC-ECD (12.5% vs. 1.1%, p<0.01). There was no significant difference in the frequency of BRAF fusions. NC-ECD patients exhibited a higher rate of MAP2K1 mutations (25.0% vs. 5.4%, p<0.01). Other frequently mutated genes included KRAS (4.0%), NRAS (2.4%), and CSF1R (2.4%), although no significant difference was observed in their frequency between C-ECD and NC-ECD. Testicular involvement appeared to be more common in patients with MAP2K1 mutations (23.1% vs. 8%, p=0.08). Two patients with pathogenic CSF1R mutations both had central nervous system (CNS) involvement. Among C-ECD patients, BRAFV600E conferred a higher rate of CNS involvement (50.9% vs. 25%, p=0.01). No significant difference was observed in NC-ECD patients (71.4% vs 36%, p=0.09). Among NC-ECD cases, MAP2K1 mutations conferred a reduced risk of cardiac involvement (37.5% vs. 79.2%, p=0.03) and no such difference was observed in patients with C-ECD (40% vs 34.1%, p=0.79). The median numbers of organs involved in patients with BRAF, MAP2K1, and KRAS/NRAS mutations were 5, 3, and 3, respectively, with no significant difference. Conclusions: C-ECD affects more organs and more frequently involves bones, adrenal glands, and sinuses. AVP-D was exclusively observed in C-ECD. Conversely, NC-ECD showed a higher prevalence of cardiac involvement. BRAFV600E was more commonly identified in C-ECD, whereas non-V600 mutations and MAP2K1 mutations were more prevalent in NC-ECD. Among C-ECD patients, BRAFV600E was correlated with a greater likelihood of CNS involvement. Conversely, NC-ECD patients with MAP2K1 mutations had a reduced risk of cardiac involvement. This study highlights the distinct clinical and molecular features of C-ECD and NC-ECD, underscoring the importance of subclassifying ECD into classical and non-classical forms. Further studies are needed to explore differences in the clinical outcomes between the 2 forms.

Introduction: Autoimmunity in Rosai-Dorfman disease (RDD) has been reported in several case reports and small case series. The recent consensus RDD guidelines even classify “immune-related RDD” as a distinct entity, but little is known about the prevalence and patterns of autoimmune conditions in this rare disease. We conducted this study to evaluate a large cohort of patients with RDD for concomitant autoimmunity. Methods: We conducted a retrospective review of cases diagnosed with RDD from five referral centers globally. Data pertaining to autoimmunity were captured in terms of serology and a clinical diagnosis of autoimmune disease (AID) and compared to previously reported prevalence of AID and autoimmunity in the general population and in patients with other lymphomas. Results: We included 157 patients diagnosed with RDD from 2003-2023. Median age at the time of RDD diagnosis was 48 years, IQR 35.5-60. This included 103 females (65.6%) and 54 male (34.4%). Racial distribution included 54 Black (34.4%), 52 White (33.1%), 40 Asian (25.5%), 7 Middle Eastern (4.5%) and 4 other (2.5%). 83 patients had multi-systemic disease (52.8%) and 74 had single organ involvement (47.2%). Most common organs involved were skin/subcutaneous tissue (78, 49.7%), lymph nodes (63, 40.1%), bone (54, 34.2%). Tissue next generation sequencing data was available for 100 patients (63.7 %) and showed KRAS mutation (19, 19 %), MAP2K/MEK (13, 13%), other mutations (27, 27 %), and no mutations (41, 41%). Mean ESR at diagnosis of RDD was 28.42 mm/Hr and mean CRP was 19.5 mg/L. In our cohort, 28 patients (17.8%) were diagnosed with an AID. 19 (67.8%) were diagnosed with the AID prior to the diagnosis of RDD. Most common AID was systemic lupus erythematosus (6, 21.4%), rheumatoid arthritis (5, 17.8%), autoimmune hemolytic anemia (3, 10.7%), polymyalgia rheumatica (2, 7.1%). AID was more common in female vs male (64.3% vs 35.7%, p 0.8) and were more commonly seen in patients with multisystem compared to single organ RDD (60.7% vs 39.3%, p 0.3). Mean ESR and CRP at the time of RDD diagnosis in patients with AID were 40.63 mm/Hr and 37.04 mg/L respectively. Autoimmune antibodies were tested in 90 patients (57.3%), of which 43 (47.8%) were positive for atleast one autoantibody which included 15 patients (16.7%) with AID and a positive autoantibody and 6 (6.6%) with AID and negative antibodies (p 0.01). Most common antibodies were ANA (29/83, 34.9%), 42.3% with a titer higher than 1:160. Other antibodies include RF (10/60, 16.67%), anti-neutrophilic cytoplasmic antibody (3/19, 15.8%), double stranded DNA (6/56, 10.7%). Positive Antibodies were more common in female compared to male patients (72% vs 23%, p 0.04) and in patients from China compared to North America (45.7% vs 22.6%, p 0.007). Autoantibody positivity was common in multi-system vs single organ RDD (53.5% vs 46.5%, p 0.9). Mean ESR and CRP in this group of patients were 34.54 mm/Hr and 23.93 mg/L respectively. Median duration of follow up for our cohort was 32 months (IQR 14-65). Five-year survival was 93.4%. There were a total 8 deaths reported in the cohort, none of which were in patients with underlying AID. In a multivariable analysis, AID was associated with race (odds ratio [OR] for Middle Eastern compared with Chinese, OR 7, p=0.02) but other factors like organ involvement, mutational status, sex and age at diagnosis were not significant. Conclusions: Our study reveals a high prevalence of autoimmunity in RDD, both in terms of AID (17.8 %) and positive autoantibodies (47.8 %), which is much higher than the general population rates of approximately 3% and 16% respectively, and higher than patients with non-Hodgkin lymphoma, 7.6% and 39%, respectively. There was a trend toward association of AID with multisystem RDD and among individuals from North America and Middle East compared to China, although auto-antibody positivity was more common in Chinese patients. Mean ESR and CRP at the time of diagnosis of RDD was higher in the patients who had AID. We did not find any statistically significant association between AID and autoantibody positivity with the underlying driver mutation. Nearly half of the patients with RDD who also had AID did not have a positive autoantibody, thereby implying the need of clinical evaluation for rheumatological symptoms rather than empiric serological testing. Overall, this study also highlights the need to explore the biological link between RDD and autoimmunity.

Background The American Society of Clinical Oncology (ASCO) launched the Diversity in Oncology initiative in 2017 to address the need for increased minority representation in the hematology-oncology workforce. A recent series of reports, titled “State of the Oncology Workforce in America,” published in JCO Oncology Practice in 2021 and 2022, focused on this issue. Notably, these reports did not include any data regarding the representation of Asian minorities in the field. Therefore, our objective was to assess the proportion of Asian professionals within the hematology-oncology workforce, encompassing both practitioners and trainees. Methods We conducted a comprehensive search for publicly available data regarding Asian representation among US hematology-oncology practitioners and trainees in both adult and pediatric fields. Our primary data sources included the 2020 US Census, the Association of American Medical Colleges, the Accreditation Council for Graduate Medical Education, and various professional societies. We defined practitioners to include hematologist-oncologists, gynecologic oncologists, radiation oncologists, surgical oncologists, hematopathologists, hematology-oncology nurse practitioners, hematology-oncology physician assistants, and nurses specializing in hematology-oncology. Trainees encompassed fellows and residents. Additionally, we gathered comparable data on the US population, medical students, adult internal medicine residents, gynecology residents, pediatric residents, pathology residents, surgery residents, nurses, nurse practitioners, and physician assistants. To provide a comprehensive overview of the hematology-oncology workforce, we utilized data from 2020 to 2022, and whenever possible, we collected longitudinal data on trainees over the years. Results As of 2020, Asians represented 6.2% of the US population. Among hematology-oncology physician practitioners, the percentage of Asian individuals ranges from 14.7% to 32.1%, including 32.1% of adult hematologist-oncologists, 20.4% of pediatric hematologist-oncologists, 25.9% of radiation oncologists, 14.7% of gynecologic oncologists, and 7.0% of hematology-oncology physician assistants. In the realm of physician trainees, Asian representation is between 17.9% and 35.3%, with 35.3% of adult hematology-oncology fellows, 20.0% of pediatric hematology-oncology fellows, 26.4% of radiation oncology residents, and 17.9% of gynecologic oncology fellows. Additionally, the proportion of Asian residents from which hematology-oncology fellows are drawn ranges from 14.9% to 35.9%. Specifically, 35.9% of internal medicine residents, 22.0% of pediatric residents, 14.9% of gynecology residents, 26.6% of pathology residents, and 19.2% of surgical residents are Asian. Furthermore, 26.7% of medical students identify as Asian. Notably, the proportions of Asian hematology-oncology trainees and medical students have remained relatively stable from 2005 to 2022. Data on hematopathologists, surgical oncologists, and non-physician practitioners are limited, although Asian representation among hematology-oncology physician assistants is 7.0% and among nurses is 7.2%. Conclusions Asians comprise a large segment of the hematology-oncology workforce in the US. While only 1 in 20 people in the US are Asians, between 1 in 3 and 1 in 5 hematology-oncology physician practitioners and trainees, are Asians. Data are limited for non-physician practitioners. Asian minority representation should be highlighted and considered as an example of success in diversity in hematology-oncology workforce. This framework should be embraced moving forward to continue advancing minority representation throughout the field of hematology-oncology.

Introduction MYD88 L265P mutations (MUT) are found in 90% of patients with Waldenstrom macroglobulinemia (WM) and lead to the activation of pro-survival signaling. Limited literature has demonstrated that patients with MYD88 wild-type (WT) WM have poorer responses to conventional therapies and a higher likelihood of histological transformation. Increasingly the role of non-coding genomics in lymphomagenesis has demonstrated importance and currently, the epigenetic landscape of MYD88 WT WM remains underexplored. This study utilized a multi-omics approach to assess DNA methylation in MYD88 WT WM compared to MYD88 MUT patients and controls. Methods Bone marrow samples were prospectively collected from 20 subjects [3 MYD88 WT/CXCR4 WT WM, 12 MYD88 MUT WM and 5 normal controls] and positive selection for CD19+ and/or CD138+ B cells was performed. The analysis focused on the comparison between MYD88 WT WM to normal controls and MYD88-WT to MUT WM. Genome-wide DNA methylation analysis was performed, and CpG methylation ratios were segmented into 200-bp regions. Differentially methylated regions (DMRs) were determined using a Q-value <0.05 and absolute methylation difference ≥10%. Next, RNA-seq data was interrogated and differentially expressed genes (log2fold change>0.5 or <-0.5, false discovery rate<0.05) with corresponding promoter hypo- or hypermethylation were assessed. Ingenuity Pathway Analysis was used to determine potentially epigenetically regulated pathways using a corrected p<0.05. Results Comparing MYD88 WT WM samples to controls, a statistically greater number of hypermethylated DMRs were observed across genomic regions (hyper- vs hypomethylated): promoter (29129 vs 6300), 3'untranslated region (UTR) (2068 vs 1551), 5'UTR (10169 vs 735), intron (30344 vs 24511), exon (2224 vs 6855), CpG island (30372 vs 1240) and CpG shore (14477 vs 5872) (all p<0.001). Next, mRNA analysis demonstrated that 214 genes were differentially up-/downregulated with concordant promoter hypo-/hypermethylation. On the assessment of promoter-methylation-based pathways, multiple pathways involved in cell signaling, proliferation, gene regulation, cytokine and immune signaling and metabolism were found to be deregulated. Most pathways were found to be negatively enriched in MYD88 WT patients compared to controls including several members of interleukin (IL) signaling (IL-2, IL-3, IL,7) and regulators of cell proliferation and signaling including mTOR, PI3K/AKT, and p53. Positive enrichment of the PTEN, FGFR3 and ERK/MAPK pathways were observed. Underlying multiple pathways was promoter hypermethylation with corresponding mRNA downregulation of AKT3 and PIK3CA. Furthermore, promoter hypomethylation with transcript upregulation of PTEN was observed. Next, in comparison of MYD88 WT to MUT samples, a statistically greater number of hypermethylated DMRs were observed across genomic regions (hyper- vs hypomethylated): promoter (24829 vs 2544), 3'UTR (3534 vs 378), 5'UTR (6111 vs 605), intron (52292 vs 5360), exon (21066 vs 2187), CpG island (18334 vs 1551) and CpG shore (16351 vs 1957) (all p<0.001). Assessing mRNA expression, 354 genes were up-/downregulated with concordant promoter hypo-/hypermethylation. Pathway analysis revealed positive enrichment of the mitotic G1 phase to G1/S transition pathway with upregulation of the CDK4, LYN, and PSMA6 transcripts in MYD88 WT compared to MUT samples. Further, negative enrichment of cell signaling regulators including the RHO GTPase family, IL pathways (IL-4, IL-8, IL-13, IL-17) and integrin signaling were found in MYD88 WT compared to MUT samples. Underlying multiple pathways were downregulation with promoter hypermethylation of BCL2, an important regulator of apoptosis. Conclusion Genome-wide methylation analysis of MYD88 WT WM revealed a unique DNA methylation profile, with potential epigenetic alteration of key oncogenic transcripts and pathways. The negative enrichment of cell signaling and cytokine/inflammatory pathways in MYD88 WT samples compared to controls and MYD88 MUT WM suggests an epigenetic mechanism for immune evasion and potentially underlies the reduced response to conventional WM-directed therapies. Overall, this study reveals that MYD88 WT WM is epigenetically distinct from MYD88 MUT WM and regulators such as methylation may underlie the unique clinical and phenotypic properties observed.

PURPOSE BRAF and MEK inhibitors are standard treatments in histiocytic disorders, such as Erdheim-Chester disease (ECD). Some patients lack MAPK-pathway alterations, making these treatments less effective. METHODS We describe three patients with histiocytic disorders who have novel non-MAPK pathway alterations. These alterations were studied through genomic and in silico analyses when applicable, then treated with off-label medications rationally selected on the basis of genomic alterations. RESULTS Patient 1 had rapidly progressive ECD involving the CNS. A CSF1R in-frame deletion (p.S560_P566del) was identified, and in silico modeling predicted a gain-of-function mutation. This alteration was targeted with pexidartinib, which led to a clinical complete response (CR) within 2 months, and a partial response (PR) on imaging after 3 months. After 15 months, the disease became resistant to pexidartinib and transformed to histiocytic sarcoma. Patient 2 has skin-only involvement of a xanthogranuloma disorder. A KIF5B-FGFR1 fusion was identified on RNA sequencing and targeted with pemigatinib. At 24 months of follow-up, she remains in a clinical PR. Patient 3 has ECD involving the bone marrow, gastrointestinal tract, and subcutaneous tissues. A MEF2C-FLT3 fusion was identified and targeted with sorafenib. He achieved a clinical CR and radiographic PR within 3 months, which has continued for 30 months. CONCLUSION We report three patients with histiocytic disorders harboring novel alterations who had sustained responses to off-label kinase inhibitors specific to their histiocytic disorder. Pathogenic variants outside of the MAPK pathway, including variants of unknown significant, may be targeted with readily available small molecules.

Lin et al. report the long‐term follow‐up of a phase II trial involving 95 adult patients with Langerhans cell histiocytosis (LCH), investigating the combination of methotrexate and cytarabine (MA). After a median follow‐up of 6.5 years, the study showed high response rates, with 90% overall response; 55% of patients free from an event such as disease progression, poor response or death; and 93% of patients were alive, though nearly half experienced febrile neutropenia. This prospective study helps fill gaps in understanding adult LCH treatment, indicating that fixed‐duration chemotherapy can yield durable responses despite its associated risks. It emphasizes the importance of personalized treatment decisions, considering both fixed‐duration chemotherapy and continuous targeted agents based on patient and disease‐specific factors.Commentary on: Lin et al. Long term follow‐up of methotrexate and cytarabine in adult patients with Langerhans cell histiocytosis. Br J Haematol 2025; 206:576‐584.

AbstractBackgroundCrystal‐storing histiocytosis (CSH) is a rare form of histiocytosis with intralysosomal accumulations of immunoglobulins or paraproteins that aggregate as crystals. Central nervous system (CNS) involvement of CSH is uncommon but should be considered in cases of persistent parenchymal enhancement on neuroimaging.MethodsWe describe one local case of CNS CSH and 10 additional cases identified by literature review.ResultsAmong 11 CSH patients, lesions involved either the dura (2/11) or brain parenchyma (9/11). Two cases had leptomeningeal enhancement. One case had spinal cord involvement. Two cases were associated with marginal zone lymphoma; one case was associated with an immunoglobulin A‐plasma cell dyscrasia. Eight of 11 cases had outcome data available: 7/8 cases had clinical and/or radiological improvement and 1/8 had radiological stability.ConclusionsCentral nervous system involvement of CSH is rare. Potential cases should be comprehensively evaluated for lymphoma or myeloma with positron emission tomography/computed tomography (CT) of the body or alternatively, CT of the chest, abdomen, pelvis and nuclear bone scan, bone marrow biopsy, serum protein electrophoresis, and cerebrospinal fluid protein electrophoresis. Treatment is targeted toward the underlying malignancy.

Abstract Magnesium (Mg) is an essential element involved in cellular metabolism. We demonstrated that in patients with diffuse large B-cell lymphoma (DLBCL) undergoing autologous stem cell transplant (SCT), those with a serum Mg < 2.0 mg/dL at the time of transplant had worse outcomes. In this study, we aimed to learn the prognostic value of low serum Mg in patients with untreated DLBCL. We analyzed serum from 408 patients and tested 2 Mg cutpoints—low (<1.7 mg/dL) and low normal (<2.0 mg/dL), a range we found associated with lower survival in the SCT group. We found 3% of patients with low levels and 23% with low normal levels. Low normal serum Mg levels were associated with a higher stage at diagnosis, more extranodal involvement, higher international prognostic index score, lower overall survival (OS), and event-free survival. These data warrant testing Mg replacement to a target of >2.0 mg/dL to learn if survival can be improved.