Citations

Abstract Background Central nervous system (CNS) involvement by mycosis fungoides (MF) is an uncommon but serious manifestation of advanced disease. Large-cell transformation (LCT) is associated with aggressive clinical behavior and increased risk of extracutaneous dissemination; however, CNS involvement remains rare and is infrequently confirmed by molecular studies. Case Presentation: We report a 77-year-old man with a 13-year history of MF who presented with progressive generalized weakness, gait instability, and weight loss. Brain magnetic resonance imaging demonstrated multiple bilateral enhancing intraparenchymal lesions concerning for primary CNS lymphoma. Cerebrospinal fluid cytology and flow cytometry were nondiagnostic. Stereotactic biopsy of a right frontal lesion revealed diffuse infiltration of brain parenchyma by large atypical lymphoid cells with a predominantly perivascular distribution. By immunohistochemistry, the lymphocytes express CD3, TCRβF1, CD30, and demonstrate diffuse p53 overexpression, complete loss of p16, and a high proliferative index (70–80%). Comparison with a prior skin biopsy which showed typical MF morphology with limited CD30 expression (< 10% of atypical lymphocytes). Polymerase chain reaction–based T-cell receptor gene rearrangement studies performed on both CNS and skin specimens demonstrated similar clonal rearrangements, confirming CNS dissemination of the original MF clone with large-cell transformation. Discussion CNS involvement in MF is rare and may occur years after the initial diagnosis, particularly in the setting of transformation. This case highlights several important features, including multifocal intraparenchymal CNS disease, nondiagnostic cerebrospinal fluid studies, and molecular confirmation of clonal relatedness between skin and CNS lesions. These findings underscore the limitations of cerebrospinal fluid-based diagnostic studies and emphasize the importance of tissue biopsy and molecular analysis in establishing the diagnosis. Conclusion We describe a rare case of MF with large-cell transformation presenting as multifocal intraparenchymal CNS disease. Molecular demonstration of identical T-cell receptor rearrangements in skin and brain lesions provided definitive evidence of metastatic dissemination. Recognition of this rare complication is essential, as new neurologic symptoms in patients with MF should prompt evaluation for CNS involvement regardless of the extent of active cutaneous disease.

ABSTRACT We report a case of a 71‐year‐old female with acute myeloid leukemia (AML), treated with chemotherapy and hematopoietic stem cell transplant (HSCT), who developed a clonally related non‐Langerhans cell histiocytosis (NLCH). She presented with pink papules on the mid‐upper cutaneous lip and thighs 3 months following HSCT. Skin biopsies revealed a dermal proliferation of cells with eosinophilic cytoplasm. Immunohistochemistry (IHC) studies demonstrated positivity for CD68, CD163, BRAF, cyclin D1, and Factor XIIIa and negativity for CD1a, S100, MPO, and CD20. Next‐generation sequencing (NGS) with a comprehensive myeloid panel revealed corresponding pathogenic mutations to her AML, including BCOR Q176fs*40, IDH1 R132C, and TP53 Y163N, and an additional BRAF V600E mutation. Additional mutations in DNMT3A and KMT2A associated with her AML were not identified. These findings supported the diagnosis of NLCH sharing a clonal origin with the patient's AML. Work up demonstrated isolated cutaneous involvement without AML relapse; therefore, the skin lesions were treated with shave excision, topical tacrolimus 0.1% ointment, and topical clobetasol 0.05% cream without further systemic treatment. The acquired BRAF V600E mutation illustrates the potential for divergent myeloid differentiation and likely explains the emergence of a clonal NLCH after successful AML treatment. Genetic analysis in NLCH can establish clonality with associated hematologic malignancies, uncover actionable mutations, and guide treatment.

Myeloid sarcoma (MS) is a tumor mass involving any extramedullary site composed of myeloid-lineage blasts with myeloid, myelomonocytic, or monocytic differentiation. Distinguishing MS from malignant histiocytic neoplasms (MHNs) is diagnostically challenging due to morphologic and immunophenotypic overlap, particularly for MS with monocytic differentiation, which can mimic MHNs, especially the subtypes of histiocytic sarcoma and interdigitating dendritic cell sarcoma, leading to potential misdiagnosis and inappropriate management. Cyclin D1 overexpression is implicated in MHNs, but its utility in differentiating these entities has not been systematically characterized. We evaluated cyclin D1 immunostaining in 43 MS cases and 30 MHNs. The median age at MS diagnosis was 59 years (range: 0.1 to 90), while the median age at MHN diagnosis was 62 years (range: 9 to 90), with heterogeneous sites of involvement. Cyclin D1 evaluation showed 100% MHNs with strong cyclin D1 positivity in ≥50% tumor cells, compared with 7% MS with weak-to-intermediate positivity in a minor subset of tumor cells. Additional immunohistochemical evaluation showed no difference in PU.1 expression in MHNs (93%) versus MS (84%) but demonstrated a higher proportion of OCT2-positivity in MHNs over MS (52% vs. 23%, P <0.05). Our study demonstrates a high sensitivity (100%) and specificity (93%) in utilizing cyclin D1 to distinguish MHNs (mature phenotype) from MS (immature phenotype) in diagnostic practice. It is particularly valuable in challenging scenarios of MS with the absence of immature/myeloid lineage-defining markers (MPO, CD34, or CD117) and provides a cost-effective tool to resolve this diagnostic pitfall, ensuring an accurate subclassification.

Measurable residual disease (MRD) has established prognostic significance in patients with myeloid disorders; however, there is limited data regarding its prognostic and predictive value and the optimal technique for measurement in the setting of post allogeneic hematopoietic cell transplantation (allo-HCT). A multi-gene next generation sequencing (NGS) panel can overcome the limitations of conventional techniques for measurement of MRD and can shed light onto the longitudinal evolution and genomic complexity of patients undergoing allo-HCT for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). In this study, patients with AML or MDS who underwent their first allo-HCT and completed NGS testing at day +100 and were in a state of morphological remission were identified from the transplant registry of Mayo Clinic in Florida. The primary aim was to evaluate the prognostic impact of somatic variants detected via NGS at day +100 post allo-HCT on long-term outcomes. In total, 105 patients who underwent allo-HCT for AML and MDS and completed NGS testing on day +100 were included in the study population. Seventeen patients were found to have detectable variants, and 88 patients were without a detectable variant. At a median follow up of 1.4 years (0.1–5.5), presence of any variant at day +100 was associated with inferior 4-year overall survival (OS) (32% vs. 69%, P < 0.001), decreased progression free survival (PFS) (34% vs. 61%, P < 0.001), and a higher incidence of relapse (64% vs. 23%, P < 0.001). In univariate models, a lower Karnofsky performance score and presence of variants post allo-HCT remained significantly associated with inferior OS, higher relapse incidence, and a decreased PFS. The presence of variants at day +100 post allo-HCT remained significant in multivariate models for relapse ( P = 0.002) but not for OS ( P = 0.06) and PFS ( P = 0.08). These results indicate that the presence of detectable somatic variants at day +100 is associated with poor long-term outcomes and are predictive of a higher incidence of relapse.

Abstract TP53 and PPM1D are key regulators of DNA damage response and repair, and somatic mutations in these genes often co-occur in hematopoietic cells, expanding under genotoxic stress. Unlike TP53 mutations, where mechanisms of progression are defined, pathways underlying clonal fitness and transformation in PPM1D mutant cells remain unclear. In collaboration with 5 academic institutions, we analyzed the clinical and molecular landscape of 337 patients with clonal hematopoiesis (CH) and clonal cytopenia of undetermined significance (CCUS) across 4 genotypes: PPM1Dmt/TP53wt (n = 170 [50%]), PPM1Dmt/TP53mt (n = 25 [7%]), TP53mt/PPM1Dwt (n = 17 [5%]), and TP53wt/PPM1Dwt (n = 125 [38%]). All PPM1D variants were truncating, located in exon 6 of the gene, with a median variant allele frequency (VAF) of 6% (range, 0.3%-64%). The PPM1Dmt/TP53mt genotype was most frequently encountered in therapy-related CH/CCUS (t-CH/t-CCUS; 80%, 66.5%, 76.5%, and 19%; P ≤ .001) and had a shorter time interval to detection from last genotoxic exposure (6.2, 5.9, 11.25, and 24.5 months; P ≤ .001) compared with PPM1Dmt/TP53wt, TP53mt/PPM1Dwt, and TP53wt/PPM1Dwt genotypes, respectively. Acknowledging the short follow-up duration, rates of malignant transformation were lower in the PPM1Dmt/TP53wt (2%) and PPM1Dmt/TP53mt (4%) groups compared with PPM1Dwt/TP53wt (12%) and PPM1Dwt/TP53mt (17%) groups (P ≤ .001), respectively. In summary, PPM1D mutations are frequently observed in t-CH/t-CCUS, with low median VAFs, and are associated with low rates of progression, even when comutated with TP53.

Abstract Anaplastic large cell lymphomas (ALCLs) are CD30+ T-cell lymphomas that share pathologic features but differ in presentation, outcome, and genetics. Current classification incorporates clinical presentation and anaplastic lymphoma kinase (ALK) status but inadequately addresses molecular heterogeneity and therapeutic vulnerabilities. We studied 689 patients with ALCL in the LLMPP (Lymphoma/Leukemia Molecular Profiling Project) and performed expert consensus review, genetic subtyping (ALK, DUSP22, TP63, and triple negative), and immunohistochemistry for phosphorylated STAT3Tyr705. RNA sequencing with unsupervised gene expression profiling in 393 patients identified 2 main molecular types of ALCL that could be predicted with 91% accuracy based on the presence (type I) or absence (type II) of phosphorylated STAT3Y705 expression. Type I ALCLs included ALK+ ALCL and a subset of triple-negative ALCLs (TN-I); type II ALCLs included tumors with DUSP22 and/or TP63 rearrangements and the remaining triple-negative ALCLs (TN-II). Type I ALCLs were enriched for JAK-STAT3, whereas type II ALCLs were enriched for non–tyrosine kinase pathways, particularly epigenetic regulators such as EZH2. Immunohistochemistry showed overexpression of EZH2 and its trimethylated substrate H3K27. Prognosis in systemic ALCL was favorable for DUSP22-rearranged ALCL (5-year overall survival, 95%) and ALK+ ALCL (88%), intermediate for triple-negative ALCL (TN-I, 52% and TN-II, 37%), and poor for TP63-rearranged ALCL (0%). We introduce an integrated molecular classification that preserves currently diagnosed ALCL entities but identifies 4 molecularly distinct ALK− ALCL subtypes (DUSP22-rearranged, TP63-rearranged, TN-I, and TN-II). This classification can be easily implemented on paraffin tissue in routine practice or clinical trials, and stratifies ALCL into diagnostically, prognostically, biologically, and potentially therapeutically relevant subtypes.

Abstract Introduction/Objective Plasmablastic lymphoma (PBL) is a rare type of B-cell lymphoma with poor prognosis. They can arise de novo in immune deficiency/dysregulation, associated with transplant or transformation of low grade lymphoma. PBL has been reported with anti-CD19 chimeric antigen receptor (CAR) T-cell therapy. Methods/Case Report 69-year-old male with CLL/SLL, treated with multiple chemotherapy regimens and was in remission. He developed generalized weaknesses. Radiology showed lymphadenopathy. Pathology was positive for DLBCL without MYC and BCL2 rearrangement. Flow cytometry revealed 1% CD5 and CD23 positive. TP53 is negative and mutated IGHV. The PD-1 was negative, favored de novo DLBCL. PET-CT and biopsy confirmed residual disease. For refractory DLBCL, CAR-T cell therapy was initiated. Patient developed PBL diffusely positive for CD138, MUM1, c-MYC and kappa; negative for CD19, CD20, PAX5, CD10, BCL6 and CD79a. MIB-1 was 90%. EBV and HHV8 were negative. BCMA was &gt;95 %, Teclistamab was initiated. The renal function deteriorated and proceeded with palliative care. Results NA Conclusion The nature of Richter transformation or de novo DLBCL into PBL in the setting of immunomodulation with CAR-T is rare occurrence. Molecular and clonality studies are needed to evaluate the pathways of losing B-cell markers to evade lineage specific therapy.

Acquired angioedema due to C1-inhibitor deficiency (AAE-C1INH) is a rare condition characterized by the localized swelling of the deeper skin layers and mucous membranes, especially the face, lips, tongue, throat, and gastrointestinal tract. AAE-C1INH is strongly associated with lymphoproliferative disorders, although it can also be linked to autoimmune conditions, solid tumors, infections, or even occur without an identifiable cause. We present the case of a 45-year-old female patient with complaints of recurrent abdominal pain, bloating, and joint swelling. Laboratory testing showed decreased C1q and C4 complement levels, and C1 esterase inhibitor levels, indicative of AAE-C1INH. Further work up confirmed a diagnosis of extranodal marginal zone lymphoma with involvement of the bone marrow and spleen. Treatment with rituximab led to resolution of angioedema symptoms and almost complete remission of underlying lymphoma. This case underscores the importance of evaluating an underlying lymphoproliferative disorder in AAE-C1INH. Therefore, the early participation of a multidisciplinary team including specialists in immunology, hematology, and oncology is necessary for appropriate management.