Assessment and management of upper limb lymphoedema in advanced disease: a case study.

Lymphoedema is thought to affect around 200 000 people in the UK (NHS England, 2023). Secondary lymphoedema is a relatively common complication of cancer and cancer treatment, and in advanced disease it may present a challenging issue for community nursing staff caring for patients approaching the end of their lives. In this article, a case study considers the assessment and treatment of upper limb lymphoedema in a patient with advanced metastatic breast cancer. Management of this complex and distressing condition requires holistic assessment and collaborative care planning with the patient and their wider care team, including onward referral to specialist lymphoedema and palliative care services. The case study considers the typical presentation of lymphoedema in an upper limb, exclusion of reversible causes for oedema, awareness of palliative care emergencies such as superior vena cava obstruction, and the provision of supportive therapeutic interventions in context of the patient's expressed wishes for her ongoing care.

Cancer spectrum and outcomes in the Mendelian short telomere syndromes.

Short telomeres have been linked to cancer risk, yet other evidence supports them being tumor suppressive. Here, we report cancer outcomes in individuals with germline mutations in telomerase and other telomere-maintenance genes. Among 180 individuals evaluated in a hospital-based setting, 12.8% had cancer. Solid tumors were rare (2.8%); nearly all were young male DKC1 mutation carriers, and they were generally resectable with good short-term outcomes. Myelodysplastic syndrome (MDS) was most common, followed by acute myeloid leukemia (AML); they accounted for 75% of cancers. Age over 50 years was the biggest risk factor, and MDS/AML usually manifested with marrow hypoplasia and monosomy 7, but the somatic mutation landscape was indistinct from unselected patients. One- and 2-year survival were 61% and 39%, respectively, and two-thirds of MDS/AML patients died of pulmonary fibrosis and/or hepatopulmonary syndrome. In one-half of the cases, MDS/AML patients showed a recurrent peripheral blood pattern of acquired, granulocyte-specific telomere shortening. This attrition was absent in age-matched mutation carriers who did not have MDS/AML. We tested whether adult short telomere patients without MDS/AML also had evidence of clonal hematopoiesis of indeterminate potential-related mutations and found that 30% were affected. These patients also primarily suffered morbidity from pulmonary fibrosis during follow-up. Our data show that the Mendelian short telomere syndromes are associated with a relatively narrow cancer spectrum, primarily MDS and AML. They suggest that short telomere length is sufficient to drive premature age-related clonal hematopoiesis in these inherited disorders.

Limited sinonasal Rosai-Dorfman disease presenting as chronic sinusitis.

AIMS: The sinonasal tract is a common extranodal site for Rosai-Dorfman disease (RDD). Recently, histiocytes with features of RDD were identified in the clinical setting of chronic sinusitis. This study evaluates whether this phenomenon should be considered part of the RDD spectrum or classified separately as RDD-like histiocytes. METHODS AND RESULTS: We prospectively collected 13 cases showing histological features of RDD in chronic sinusitis patients and identified 14 with similar findings (3.5%) via retrospective review of 403 sinus contents over 2 years. All 27 cases displayed nodular aggregates of eosinophilic histiocytes with intermixed lymphoplasmacytic inflammation, prominent eosinophils and emperipolesis. The histiocytes were positive for S100 protein and cyclin D1 and negative for CD1a and CD207. All patients presented with severe chronic sinusitis without tumour formation or systemic symptoms. Twelve patients with follow-up (55%) required repeat sinus surgery compared with just 43 other sinusitis patients evaluated (11%); features of RDD were present in their additional specimens. Two cases that underwent targeted next-generation sequencing (20%) had oncogenic mutations in NF1 and KEAP1. CONCLUSIONS: Overall, these findings confirm diagnostic histological and immunohistochemical features of RDD in a subset of chronic sinusitis specimens. While patients uniformly lack systemic involvement or tumefactive growth, they have a high risk of recurrent sinus disease. Although the relatively subtle nature of the findings raises consideration of separate classification, the presence of occasional oncogenic mutations and evidence of consistent MAPK/ERK pathway activation via cyclin D1 positivity suggests that this phenomenon represents a unique limited manifestation of RDD.

Diagnostic utility of STAT6YE361 expression in classical Hodgkin lymphoma and related entities.

Although the distinction of classical Hodgkin lymphoma from nodular lymphocyte predominant Hodgkin lymphoma using morphology and immunostains is straightforward in most instances, occasional cases pose diagnostic challenge. We sought to determine the utility of the novel YE361 STAT6 rabbit monoclonal antibody in Hodgkin lymphoma and diagnostically challenging B- and T-cell non-Hodgkin lymphoma entities with Hodgkin-like features. Cases from seven institutions included: 57 classical Hodgkin lymphomas (31% EBV+), 34 nodular lymphocyte predominant Hodgkin lymphomas, 34 mimicking B- and T-cell non-Hodgkin lymphomas, and 7 reactive lymphoproliferations. After review of histology, STAT6YE361 immunostaining was performed. The intensity and spatial localization of immunopositivity was assessed in neoplastic cells. Additional FISH for programmed death ligand-1 (PD-L1) was performed in one patient in paired treatment-naive and relapse biopsy tissues. Two STAT6YE361 immunopositive cases were examined by whole-exome sequencing after flow sorting to assess mutations in STAT6 pathway genes. Most classical Hodgkin lymphomas showed nuclear staining for STAT6YE361 [46/57 cases (80%)] on Hodgkin cells. Staining was exclusively nuclear in a minority [12/46 (26%)], while dual nuclear and cytoplasmic localization was more common [34/46 (74%)]. In contrast, all nodular lymphocyte predominant Hodgkin lymphomas [0/34 (0%)] were negative for nuclear STAT6YE361 staining on the lymphocyte predominant cells. Within B- and T-cell non-Hodgkin lymphomas, nuclear STAT6YE361 was seen in: B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, and in primary mediastinal large B-cell lymphoma. Strong PD-L1 gene amplification was noted in the paired cHL and relapse B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, although STAT6YE361 was negative in both biopsies. Whole-exome sequencing identified mutations in B2M, XPO1, and ITPKB as well CISHP213L (in the STAT pathway) in one classical Hodgkin lymphoma patient positive for nuclear STAT6YE361 although no underlying STAT6 mutations were observed in either sample examined. STAT6YE361 nuclear staining has 100% positive predictive value and 85.7% negative predictive value in confirming or excluding classical Hodgkin lymphoma diagnosis in the distinction from nodular lymphocyte predominant Hodgkin lymphoma and other benign and malignant entities.

FLT3-ITD cooperates with Rac1 to modulate the sensitivity of leukemic cells to chemotherapeutic agents via regulation of DNA repair pathways.

Acute myeloid leukemia (AML) is an aggressive hematologic neoplasm, and patients with an internal tandem duplication (ITD) mutation of the FMS-like tyrosine kinase-3 (FLT3) receptor gene have a poor prognosis. FLT3-ITD interacts with DOCK2, a G effector protein that activates Rac1/2. Previously, we showed that knockdown of DOCK2 leads to decreased survival of FLT3-ITD leukemic cells. We further investigated the mechanisms by which Rac1/DOCK2 activity affects cell survival and chemotherapeutic response in FLT3-ITD leukemic cells. Exogenous expression of FLT3-ITD led to increased Rac1 activity, reactive oxygen species, phosphorylated STAT5, DNA damage response factors and cytarabine resistance. Conversely, DOCK2 knockdown resulted in a decrease in these factors. Consistent with the reduction in DNA damage response factors, FLT3-ITD cells with DOCK2 knockdown exhibited significantly increased sensitivity to DNA damage response inhibitors. Moreover, in a mouse model of FLT3-ITD AML, animals treated with the CHK1 inhibitor MK8776 + cytarabine survived longer than those treated with cytarabine alone. These findings suggest that FLT3-ITD and Rac1 activity cooperatively modulate DNA repair activity, the addition of DNA damage response inhibitors to conventional chemotherapy may be useful in the treatment of FLT3-ITD AML, and inhibition of the Rac signaling pathways via DOCK2 may provide a novel and promising therapeutic target for FLT3-ITD AML.

All-trans retinoic acid synergizes with FLT3 inhibition to eliminate FLT3/ITD+ leukemia stem cells in vitro and in vivo.

FMS-like tyrosine kinase 3 (FLT3)-mutant acute myeloid leukemia (AML) portends a poor prognosis, and ineffective targeting of the leukemic stem cell (LSC) population remains one of several obstacles in treating this disease. All-trans retinoic acid (ATRA) has been used in several clinical trials for the treatment of nonpromyelocytic AML with limited clinical activity observed. FLT3 tyrosine kinase inhibitors (TKIs) used as monotherapy also achieve limited clinical responses and are thus far unable to affect cure rates in AML patients. We explored the efficacy of combining ATRA and FLT3 TKIs to eliminate FLT3/internal tandem duplication (ITD)(+) LSCs. Our studies reveal highly synergistic drug activity, preferentially inducing apoptosis in FLT3/ITD(+) cell lines and patient samples. Colony-forming unit assays further demonstrate decreased clonogenicity of FLT3/ITD(+) cells upon treatment with ATRA and TKI. Most importantly, the drug combination depletes FLT3/ITD(+) LSCs in a genetic mouse model of AML, and prolongs survival of leukemic mice. Furthermore, engraftment of primary FLT3/ITD(+) patient samples is reduced in mice following treatment with FLT3 TKI and ATRA in combination, with evidence of cellular differentiation occurring in vivo. Mechanistically, we provide evidence that the synergism of ATRA and FLT3 TKIs is at least in part due to the observation that FLT3 TKI treatment upregulates the antiapoptotic protein Bcl6, limiting the drug's apoptotic effect. However, cotreatment with ATRA reduces Bcl6 expression to baseline levels through suppression of interleukin-6 receptor signaling. These studies provide evidence of the potential of this drug combination to eliminate FLT3/ITD(+) LSCs and reduce the rate of relapse in AML patients with FLT3 mutations.

Peripheral T-cell lymphomas of follicular helper T-cell type frequently display an aberrant CD3(-/dim)CD4(+) population by flow cytometry: an important clue to the diagnosis of a Hodgkin lymphoma mimic.

Nodal follicular helper T-cell-derived lymphoproliferations (specifically the less common peripheral T-cell lymphomas of follicular type) exhibit a spectrum of histologic features that may mimic reactive hyperplasia or Hodgkin lymphoma. Even though angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma of follicular type share a common biologic origin from follicular helper T-cells and their morphology has been well characterized, flow cytometry of peripheral T-cell lymphomas of follicular type has not been widely discussed as a tool for identifying this reactive hyperplasia/Hodgkin lymphoma mimic. We identified 10 peripheral T-cell lymphomas of follicular type with available flow cytometry data from five different institutions, including two cases with peripheral blood evaluation. For comparison, we examined flow cytometry data for 8 classical Hodgkin lymphomas (including 1 lymphocyte-rich classical Hodgkin lymphoma), 15 nodular lymphocyte predominant Hodgkin lymphomas, 15 angioimmunoblastic T-cell lymphomas, and 26 reactive nodes. Lymph node histology and flow cytometry data were reviewed, specifically for the presence of a CD3(-/dim)CD4(+) aberrant T-cell population (described in angioimmunoblastic T-cell lymphomas), besides other T-cell aberrancies. Nine of 10 (90%) peripheral T-cell lymphomas of follicular type showed a CD3(-/dim)CD4(+) T-cell population constituting 29.3% (range 7.9-62%) of all lymphocytes. Five of 10 (50%) had nodular lymphocyte predominant Hodgkin lymphoma or lymphocyte-rich classical Hodgkin lymphoma-like morphology with scattered Hodgkin-like cells that expressed CD20, CD30, CD15, and MUM1. Three cases had a nodular growth pattern and three others exhibited a perifollicular growth pattern without Hodgkin-like cells. Epstein-Barr virus was positive in 1 of 10 cases (10%). PCR analysis showed clonal T-cell receptor gamma gene rearrangement in all 10 peripheral T-cell lymphomas of follicular type. By flow cytometry, 11 of 15 (73.3%) angioimmunoblastic T-cell lymphomas showed the CD3(-/dim)CD4(+) population (mean: 19.5%, range: 3-71.8%). Using a threshold of 3% for CD3(-/dim)CD4(+) T cells, all 15 nodular lymphocyte predominant Hodgkin lymphoma controls and 8 classical Hodgkin lymphomas were negative (Mann-Whitney P=0.01, F-PTCL vs Hodgkin lymphomas), as were 25 of 26 reactive lymph nodes. The high frequency of CD3(-/dim)CD4(+) aberrant T cells is similar in angioimmunoblastic T-cell lymphomas and peripheral T-cell lymphomas of follicular type, and is a useful feature in distinguishing peripheral T-cell lymphomas of follicular type from morphologic mimics such as reactive hyperplasia or Hodgkin lymphoma.

TTT-3002 is a novel FLT3 tyrosine kinase inhibitor with activity against FLT3-associated leukemias in vitro and in vivo.

More than 35% of acute myeloid leukemia (AML) patients harbor a constitutively activating mutation in FMS-like tyrosine kinase-3 (FLT3). The most common type, internal tandem duplication (ITD), confers poor prognosis. We report for the first time on TTT-3002, a tyrosine kinase inhibitor (TKI) that is one of the most potent FLT3 inhibitors discovered to date. Studies using human FLT3/ITD mutant leukemia cell lines revealed the half maximal inhibitory concentration (IC50) for inhibiting FLT3 autophosphorylation is from 100 to 250 pM. The proliferation IC50 for TTT-3002 in these same cells was from 490 to 920 pM. TTT-3002 also showed potent activity when tested against the most frequently occurring FLT3-activating point mutation, FLT3/D835Y, against which many current TKIs are ineffective. These findings were validated in vivo by using mouse models of FLT3-associated AML. Survival and tumor burden of mice in several FLT3/ITD transplantation models is significantly improved by administration of TTT-3002 via oral dosing. Finally, we demonstrated that TTT-3002 is cytotoxic to leukemic blasts isolated from FLT3/ITD-expressing AML patients, while displaying minimal toxicity to normal hematopoietic stem/progenitor cells from healthy blood and bone marrow donors. Therefore, TTT-3002 has demonstrated preclinical potential as a promising new FLT3 TKI in the treatment of FLT3-mutant AML.

Hematolymphoid lesions of the sinonasal tract.

Various hematolymphoid lesions involve the sinonasal tract, including aggressive B, T, and NK-cell neoplasms; myeloid sarcoma; low-grade lymphomas; indolent T-lymphoblastic proliferations; and Rosai-Dorfman disease. Differentiating aggressive lymphomas from non-hematopoietic neoplasms such as poorly differentiated squamous cell carcinoma, olfactory neuroblastoma, or sinonasal undifferentiated carcinoma may pose diagnostic challenges. In addition, the necrosis, vascular damage, and inflammatory infiltrates that are associated with some hematolymphoid disorders can result in misdiagnosis as infectious, autoimmune, or inflammatory conditions. Here, we review hematolymphoid disorders involving the sinonasal tract including their key clinical and histopathologic features.

FLT3/D835Y mutation knock-in mice display less aggressive disease compared with FLT3/internal tandem duplication (ITD) mice.

FMS-like tyrosine kinase 3 (FLT3) is mutated in approximately one third of acute myeloid leukemia cases. The most common FLT3 mutations in acute myeloid leukemia are internal tandem duplication (ITD) mutations in the juxtamembrane domain (23%) and point mutations in the tyrosine kinase domain (10%). The mutation substituting the aspartic acid at position 838 (equivalent to the human aspartic acid residue at position 835) with a tyrosine (referred to as FLT3/D835Y hereafter) is the most frequent kinase domain mutation, converting aspartic acid to tyrosine. Although both of these mutations constitutively activate FLT3, patients with an ITD mutation have a significantly poorer prognosis. To elucidate the mechanisms behind this prognostic difference, we have generated a knock-in mouse model with a D838Y point mutation in FLT3 that corresponds to the FLT3/D835Y mutation described in humans. Compared with FLT3/ITD knock-in mice, the FLT3/D835Y knock-in mice survive significantly longer. The majority of these mice develop myeloproliferative neoplasms with a less-aggressive phenotype. In addition, FLT3/D835Y mice have distinct hematopoietic development patterns. Unlike the tremendous depletion of the hematopoietic stem cell compartment we have observed in FLT3/ITD mice, FLT3/D835Y mutant mice are not depleted in hematopoietic stem cells. Further comparisons of these FLT3/D835Y knock-in mice with FLT3/ITD mice should provide an ideal platform for dissecting the molecular mechanisms that underlie the prognostic differences between the two different types of FLT3 mutations.

Long interspersed element-1 protein expression is a hallmark of many human cancers.

Cancers comprise a heterogeneous group of human diseases. Unifying characteristics include unchecked abilities of tumor cells to proliferate and spread anatomically, and the presence of clonal advantageous genetic changes. However, universal and highly specific tumor markers are unknown. Herein, we report widespread long interspersed element-1 (LINE-1) repeat expression in human cancers. We show that nearly half of all human cancers are immunoreactive for a LINE-1-encoded protein. LINE-1 protein expression is a common feature of many types of high-grade malignant cancers, is rarely detected in early stages of tumorigenesis, and is absent from normal somatic tissues. Studies have shown that LINE-1 contributes to genetic changes in cancers, with somatic LINE-1 insertions seen in selected types of human cancers, particularly colon cancer. We sought to correlate this observation with expression of the LINE-1-encoded protein, open reading frame 1 protein, and found that LINE-1 open reading frame 1 protein is a surprisingly broad, yet highly tumor-specific, antigen.

Impact of flow cytometry in liver cytopathology.

BACKGROUND: Fine needle aspiration (FNA) is commonly used as a diagnostic tool for the evaluation of lymphoproliferative diseases. Cytomorphology alone is often insufficient for the diagnosis and subclassification of lymphoma; therefore, flow cytometry (FC) plays an important role in the characterization of lymphoproliferative disorders. This study reviews our experience with FC on liver FNA at the Johns Hopkins Hospital. METHODS: 2,424 liver FNAs performed over a 21-year period were reviewed for clinical FC data (n=74) or a subsequent diagnosis of lymphoma in the liver without FC data (n=40). RESULTS: In our study, 114 cases (4.7%) were included out of the 2,424 liver FNAs performed during the study period. Lymphoma was diagnosed 79 times. Cytomorphology alone was diagnostic of lymphoma in 45 cases, and in 33 cases both the cytomorphology and the FC were consistent with a diagnosis of lymphoma. Neither FC nor cytomorphology were diagnostic of lymphoma on 1 specimen. In 39 cases, FC had negative results on a lesion suspicious for lymphoma based on cytomorphology. In several nonlymphoma cases, FC provided information that allowed further subclassification of the neoplasm. CONCLUSION: FC is a useful adjuvant diagnostic test for liver FNAs performed on patients with lymphoproliferative disorders.

Knock-in of a FLT3/ITD mutation cooperates with a NUP98-HOXD13 fusion to generate acute myeloid leukemia in a mouse model.

Constitutive activation of FLT3 by internal tandem duplication (ITD) is one of the most common molecular alterations in acute myeloid leukemia (AML). FLT3/ITD mutations have also been observed in myelodysplastic syndrome patients both before and during progression to AML. Previous work has shown that insertion of an FLT3/ITD mutation into the murine Flt3 gene induces a myeloproliferative neoplasm, but not progression to acute leukemia, suggesting that additional cooperating events are required. We therefore combined the FLT3/ITD mutation with a model of myelodysplastic syndrome involving transgenic expression of the Nup98-HoxD13 (NHD13) fusion gene. Mice expressing both the FLT3/ITD and NHD13 transgene developed AML with 100% penetrance and short latency. These leukemias were driven by mutant FLT3 expression and were susceptible to treatment with FLT3 tyrosine kinase inhibitors. We also observed a spontaneous loss of the wild-type Flt3 allele in these AMLs, further modeling the loss of the heterozygosity phenomenon that is seen in human AML with FLT3-activating mutations. Because resistance to FLT3 inhibitors remains an important clinical issue, this model may help identify new molecular targets in collaborative signaling pathways.

Primary effusion lymphoma presenting as a cutaneous intravascular lymphoma.

Primary effusion lymphoma (PEL) is a rare and aggressive lymphoma that arises in the context of immunosuppression and is characterized by co-infection with Epstein-Barr virus (EBV) and human herpesvirus-8/Kaposi sarcoma-associated herpesvirus (HHV-8/KSHV). It was originally described as arising in body cavity effusions, but presentation as a mass lesion (extracavitary PEL) is now recognized. Here, we describe a case of PEL with an initial presentation as an intravascular lymphoma with associated skin lesions. The patient was a 53-year-old man with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) who presented with fevers, weight loss and skin lesions concerning for Kaposi sarcoma (KS). A skin biopsy revealed no evidence of KS; however, dermal vessels contained large atypical cells that expressed CD31 and plasma cell markers but lacked most B- and T-cell antigens. The atypical cells expressed EBV and HHV-8. The patient subsequently developed a malignant pleural effusion containing the same neoplastic cell population. The findings in this case highlight the potential for unusual intravascular presentations of PEL in the skin as well as the importance of pursuing microscopic diagnosis of skin lesions in immunosuppressed patients.

Inhibition of NOTCH4 sensitizes FLT3/ITD acute myeloid leukemia cells to FLT3 tyrosine kinase inhibition.

Internal tandem duplication mutations of FLT3 (FLT3/ITD) confer poor prognosis in AML. FLT3 tyrosine kinase inhibitors (TKIs) alone have limited and transient clinical efficacy thus calling for new targets for more effective combination therapy. In a loss-of-function RNAi screen, we identified NOTCH4 as one such potential target whose inhibition proved cytotoxic to AML cells, and also sensitized them to FLT3 inhibition. Further investigation found increased NOTCH4 expression in FLT3/ITD AML cell lines and primary patient samples. Inhibition of NOTCH4 by shRNA knockdown, CRISPR-Cas9-based knockout or γ-secretase inhibitors synergized with FLT3 TKIs to kill FLT3/ITD AML cells in vitro. NOTCH4 inhibition sensitized TKI-resistant FLT3/ITD cells to FLT3 TKI inhibition. The combination reduced phospho-ERK and phospho-AKT, indicating inhibition of MAPK and PI3K/AKT signaling pathways. It also led to changes in expression of genes involved in regulating cell cycling, DNA repair and transcription. A patient-derived xenograft model showed that the combination reduced both the level of leukemic involvement of primary human FLT3/ITD AML cells and their ability to engraft secondary recipients. In summary, these results demonstrate that NOTCH4 inhibition synergizes with FLT3 TKIs to eliminate FLT3/ITD AML cells, providing a new therapeutic target for AML with FLT3/ITD mutations.

Targeted pathologic evaluation of bone marrow donors identifies previously undiagnosed marrow abnormalities.

Potential bone marrow donors are screened to ensure the safety of both the donor and recipient. At our institution, potential donors with abnormal peripheral blood cell counts, a personal history of malignancy, or age >60 years are evaluated to ensure that they are viable candidates for donation. Evaluation of the marrow includes morphologic, flow cytometric, and cytogenetic studies. A total of 122 potential donors were screened between the years of 2001 and 2011, encompassing approximately 10% of all donors. Of the screened potential donors, the mean age was 59 years and there were 59 men and 63 women. The donors were screened because of age >60 years (n = 33), anemia (n = 22), cytopenias other than anemia (n = 27), elevated peripheral blood counts without a concurrent cytopenia (n = 20), elevated peripheral blood counts with a concurrent cytopenia (n = 10), history of malignancy (n = 4), abnormal peripheral blood differential (n = 3), prior graft failure (n = 1), history of treatment with chemotherapy (n = 1), and body habitus (n = 1). Marrow abnormalities were detected in 9% (11 of 122) of donors. These donors were screened because of anemia (5 of 22, 23%), age >60 years (2 of 33, 6%), history of malignancy (2 of 4, 50%), elevated peripheral blood counts (1 of 20, 5%), and body habitus (1 of 1, 100%). Abnormalities included plasma cell dyscrasia (n = 3), abnormal marrow cellularity (n = 3), clonal cytogenetic abnormalities (n = 2), low-grade myelodysplastic syndrome (1), a mutated JAK2 V617F allele (n = 1), and monoclonal B cell lymphocytosis (n = 1). Our experience indicates that extended screening of potential donors identifies a significant number of donors with previously undiagnosed marrow abnormalities.

International Consensus Classification of acute lymphoblastic leukemia/lymphoma.

The updated International Consensus Classification (ICC) of B-acute lymphoblastic leukemia (B-ALL) and T-acute lymphoblastic leukemia (T-ALL) includes both revisions to subtypes previously outlined in the 2016 WHO classification and several newly described entities. The ICC classification incorporates recent clinical, cytogenetic, and molecular data, with a particular emphasis on whole transcriptome analysis and gene expression (GEX) clustering studies. B-ALL classification is modified to further subclassify BCR::ABL1-positive B-ALL and hypodiploid B-ALL. Additionally, nine new categories of B-ALL are defined, including seven that contain distinguishing gene rearrangements, as well as two new categories that are characterized by a specific single gene mutation. Four provisional entities are also included in the updated B-ALL classification, although definitive identification of these subtypes requires GEX studies. T-ALL classification is also updated to incorporate BCL11B-activating rearrangements into early T-precursor (ETP) ALL taxonomy. Additionally, eight new provisional entities are added to the T-ALL subclassification. The clinical implications of the new entities are discussed, as are practical approaches to the use of different technologies in diagnosis. The enhanced specificity of the new classification will allow for improved risk stratification and optimized treatment plans for patients with ALL.

Transdifferentiation, phenotypic infidelity, progression, and transformation in T/NK-cell neoplasms: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: Sessions 8 and 9 of the 2021 Society for Hematopathology and the European Association for Haematopathology Workshop aimed to collect examples of transdifferentiation, lineage infidelity, progression, and transformation in precursor and mature T/natural killer (NK)-cell neoplasms. METHODS: Twenty-eight cases were submitted and analyzed, with whole-exome sequencing and genome-wide RNA expression analysis performed in a subset of the cases. RESULTS: In session 8, 7 T-lymphoblastic lymphoma/leukemia cases were received that showed transdifferentiation to clonally related mature myeloid hematopoietic neoplasms, including 6 histiocytic/dendritic cell lineage neoplasms and a mast cell sarcoma. Session 9 included 21 mature T-cell neoplasms that were grouped into 3 themes. The first one addressed phenotypic infidelity in mature T-cell lymphomas (TCLs) and included 8 TCLs expressing aberrant antigens, mimicking classic Hodgkin and non-Hodgkin B-cell lymphomas. The second theme addressed disease progression in TCL and included 5 cutaneous T-cell lymphoproliferative disorders and 2 T-cell large granular lymphocyte proliferations with subsequent progression to systemic TCL. The third theme included 6 patients with TCL with T-follicular helper phenotype, mainly angioimmunoblastic T-cell lymphoma, with concurrent/subsequent clonal hematopoiesis or myeloid neoplasms and/or subsequent/concomitant diffuse large B-cell lymphoma. CONCLUSIONS: This cohort of cases allowed us to illustrate, discuss, and review current concepts of transdifferentiation, aberrant antigen expression, and progression in various T/NK-cell neoplasms.