An Unusual Case Study of Idiopathic Bilateral Deep Vein Thrombosis and Osteonecrosis of the Left Distal Tibia in an 11-year-old Girl.

Introduction: Deep vein thrombosis (DVTs) in children is rare, normally linked to pathologies such as major traumatic injury, thrombophilia, and malignancy. Osteonecrosis is still poorly understood. There is growing support to include hypercoagulable states as a predisposing factor, however, no definitive correlation has been found. At present, there are no conclusive literature on the links between osteonecrosis and DVT. Case Presentation: This report describes an unusual and rare case of osteonecrosis and idiopathic DVT in an 11-year-old girl who initially presented with a sprained left ankle. On follow-up, pain was persistent and subsequent radiological investigations revealed extensive DVT, and magnetic resonance imaging scan revealed osteonecrosis of the distal left tibia. Initial blood tests were normal, however with follow-up with hematology, a diagnosis of antithrombin deficiency was made, with the treatment of lifelong anticoagulation. Our patient had continued orthopedic input for clinical and radiographic surveillance to monitor leg length discrepancy. Conclusion: This case highlights the need to engage in close follow-up and the cautionary care required when young children present with non-resolving severe pain, to consider osteonecrosis and DVT. Our case also highlights the need for further research into the relationship between minor injuries and DVTs and osteonecrosis in children, and the potential synergistic relationship between DVTs and osteonecrosis.

Preclinical Characterization and Phase I Study of an Anti-HER2-TLR7 Immune-Stimulator Antibody Conjugate in Patients with HER2+ Malignancies.

Immune-stimulator antibody conjugates (ISAC) combining tumor-targeting monoclonal antibodies with immunostimulatory agents allow targeted delivery of immune activators into tumors. NJH395 is a novel, first-in-class ISAC comprising a Toll-like receptor 7 (TLR7) agonist conjugated to an anti-HER2 antibody via a noncleavable linker payload. Preclinical characterization showed ISAC-mediated activation of myeloid cells in the presence of antigen-expressing cancer cells, with antigen targeting and TLR7 agonism contributing to antitumor activity. Safety, efficacy, immunogenicity, pharmacokinetics, and pharmacodynamics were investigated in a phase I, multicenter, open-label study in patients with HER2+ non-breast advanced malignancies (NCT03696771). Data from 18 patients enrolled in single ascending dose escalation demonstrated delivery of the TLR7-agonist payload in HER2+ tumor cells and induction of type I IFN responses, which correlated with immune modulation in the tumor microenvironment. Cytokine release syndrome was a common, but manageable, drug-related adverse event. Antidrug antibodies and neuroinflammation at high doses represented significant clinical challenges. Data provide proof-of-mechanism and critical insights for novel immunotherapies.

The diagnostic challenges and clinical course of a myeloid/lymphoid neoplasm with eosinophilia and ZBTB20-JAK2 gene fusion presenting as B-lymphoblastic leukemia.

We report the diagnostic challenges and the clinical course of a patient with an extraordinary presentation of B-lymphoblastic leukemia (B-ALL) with eosinophilia. We identified a novel ZBTB20-JAK2 gene fusion as a chimeric RNA transcript using the Archer platform. This gene fusion from the same patient was recently identified by Peterson et al. (2019) at the genomic level using a different sequencing technology platform. The configuration of this gene fusion predicts the production of a kinase-activating JAK2 fusion protein, which would normally lead to a diagnosis of Philadelphia chromosome-like B-ALL (Ph-like B-ALL). However, the unusual presentation of eosinophilia led us to demonstrate the presence of this gene fusion in nonlymphoid hematopoietic cells by fluorescence in situ hybridization (FISH) studies with morphologic correlation. Therefore, we believe this disease, in fact, represents blast crisis arising from an underlying myeloid neoplasm with JAK2 rearrangements. This case illustrates the difficulty in differentiating Ph-like B-ALL and myeloid/lymphoid neoplasm with eosinophilia and gene rearrangements (MLN-EGR) in blast crisis. As currently defined, the diagnosis of MLN-EGR relies on the hematologic presentations and the identification of marker gene fusions (including PCM1-JAK2, ETV6-JAK2, and BCR-JAK2). However, these same gene fusions, when limited to B-lymphoblasts, also define Ph-like B-ALL. Yet, our case does not conform to either condition. Therefore, the assessment for lineage restriction of gene rearrangements to reflect the pathophysiologic difference between B-ALL and MLN-EGR in blast crisis is likely a more robust diagnostic approach and allows the inclusion of MLN-EGR with novel gene fusions.

Cytogenomic array detects a subset of myelodysplastic syndrome with increased risk that is invisible to conventional karyotype.

Conventional karyotyping is essential standard practice in the initial evaluation of myelodysplastic syndrome (MDS) and is the most impactful single component of the Revised International Prognostic Scoring System (IPSS-R). While single nucleotide polymorphism array (SNP-A) has demonstrated the ability to detect chromosomal defects with greater sensitivity than conventional karyotype, widespread adoption is limited by the unknown additional prognostic impact of SNP-A analysis. Here, we investigate the significance of additional SNP-A abnormalities in the setting of MDS and demonstrate differences in survival of patients with additional abnormalities, even those initially characterized as relatively lower risk either by cytogenetic score or IPSS-R. Our findings identify specific abnormalities, particularly KMT2A partial tandem duplication, that are invisible to conventional karyotype and potentially contribute to the poor prognosis of MDS patients. Furthermore, these results demonstrate the added value of SNP-A analysis in identifying patients who may benefit from more aggressive therapy, particularly those who would otherwise be classified into lower risk categories.

G-CSF partially mediates effects of sleeve gastrectomy on the bone marrow niche.

Bariatric surgeries are integral to the management of obesity and its metabolic complications. However, these surgeries cause bone loss and increase fracture risk through poorly understood mechanisms. In a mouse model, vertical sleeve gastrectomy (VSG) caused trabecular and cortical bone loss that was independent of sex, body weight, and diet, and this loss was characterized by impaired osteoid mineralization and bone formation. VSG had a profound effect on the bone marrow niche, with rapid loss of marrow adipose tissue, and expansion of myeloid cellularity, leading to increased circulating neutrophils. Following VSG, circulating granulocyte-colony stimulating factor (G-CSF) was increased in mice, and was transiently elevated in a longitudinal study of humans. Elevation of G-CSF was found to recapitulate many effects of VSG on bone and the marrow niche. In addition to stimulatory effects of G-CSF on myelopoiesis, endogenous G-CSF suppressed development of marrow adipocytes and hindered accrual of peak cortical and trabecular bone. Effects of VSG on induction of neutrophils and depletion of marrow adiposity were reduced in mice deficient for G-CSF; however, bone mass was not influenced. Although not a primary mechanism for bone loss with VSG, G-CSF plays an intermediary role for effects of VSG on the bone marrow niche.

Kikuchi-Fujimoto Disease: A Review.

Kikuchi-Fujimoto disease (KFD) is a rare entity characterized by subacute necrotizing lymphadenopathy and frequently associated with fever. Young adults of Asian ancestry are most commonly affected, but it has been reported worldwide. Despite many studies in the literature, the cause of KFD remains uncertain. Histologically, KFD is characterized by paracortical lymph node expansion with patchy, well-circumscribed areas of necrosis showing abundant karyorrhectic nuclear debris and absence of neutrophils and eosinophils. Three evolving histologic patterns-proliferative, necrotizing, and xanthomatous-have been recognized. By immunohistochemistry, histiocytes in KFD are positive for myeloperoxidase. There is a marked predominance of T cells in the lesions (with mostly CD8-positive cells) with very few B cells. The differential diagnosis of KFD includes infectious lymphadenitis, autoimmune lymphadenopathy (primarily systemic lupus erythematosus), and lymphoma. Clinicians and pathologists are poorly familiar with this entity, which frequently causes significant diagnostic challenges.

KRAS mutation in secondary malignant histiocytosis arising from low grade follicular lymphoma.

BACKGROUND: Transformation of follicular lymphoma most typically occurs as diffuse large B-cell lymphoma, however other forms of transformation such as classic Hodgkin lymphoma and lymphoblastic transformation can occur. Secondary malignant histiocytosis also represents a rare form of transformation, which is thought to occur due to a process of transdifferentiation whereby the lymphoma cells exhibit lineage plasticity and lose all evidence of B-cell phenotype and instead acquire the phenotype of a histiocytic neoplasm. Little is known about the underlying genetic alterations that occur during this unusual process. Comparative genetic analysis of pre- and post-transformation/transdifferentiation would be one tool by which we could better understand how this phenomenon occurs. CASE PRESENTATION: Here we report the clinical, immunophenotypic and genetic features of a rare case of secondary malignant histiocytosis, Langerhans cell-type (Langerhans cell sarcoma) arising from a previous low grade follicular lymphoma. FISH analysis confirmed the presence of IgH/BCL2 rearrangement in both the low grade follicular lymphoma (FL) and transformed Langerhans cells sarcoma (LCS) samples, demonstrating a clonal relationship. Comparative whole exome sequencing was then performed, which identified a KRAS p.G13D mutation in the LCS that was not present in the FL. CONCLUSIONS: This report highlights genetic alterations, in particular an acquired somatic KRAS mutation, that may occur during transdifferentiation, with additional significance of KRAS mutation as a possible therapeutic target in cases which otherwise would have limited treatment options.

Diagnostically relevant updates to the 2017 WHO classification of lymphoid neoplasms.

The recent 2017 WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues contains a number of updates under the category of lymphoid neoplasms. These changes include introduction of new entities, amended classification or terminology, and addition of newly discovered diagnostic and molecular features. In this review, we perform a focused, concise summary of selected lymphoid neoplasms and discuss changes in their classification. Rather than a comprehensive overview, we place specific emphasis on important and diagnostically relevant aspects of each entity that are novel or different from the previous WHO iteration and bring the practicing pathologist quickly up to speed with the updated classification.

Follicular Lymphoma Diagnostic Caveats and Updates.

CONTEXT.­: Follicular lymphoma is a common small B-cell lymphoma, likely to be encountered by any practicing pathologist, regardless of specialty. Although the features of typical follicular lymphoma are well known and in most instances easily identifiable, there are lesser-appreciated morphologic appearances that can raise alternative diagnostic possibilities. The limited tissue available in core needle biopsies can make it additionally challenging to thoroughly evaluate those features in the context of architecture. Furthermore, ancillary testing including immunohistochemistry and molecular/genetic analysis do not always show classic findings and may pose additional challenges to interpretation. OBJECTIVES.­: To review the morphologic features of follicular lymphoma with a discussion of morphologic variants and mimics; to discuss pitfalls of ancillary testing and provide the practicing pathologist with an appropriate context for interpretation of immunohistochemical and molecular/genetic studies when follicular lymphoma is part of the differential diagnosis; and to propose diagnostic strategies when there is limited tissue for evaluation. DATA SOURCES.­: We used examples of follicular lymphoma from our institution as well as a review of the literature, with a focus on the diagnostic aspects that are broadly relevant to a general pathology practice. CONCLUSIONS.­: Follicular lymphoma can occasionally present with atypical morphologic, immunohistochemical, or molecular/genetic features. In particular, those findings can be difficult to interpret in the setting of a limited tissue sample. Awareness of those possibilities will help guide the pathologist to a more accurate and precise diagnosis.

Primary myelofibrosis evolving to an aplastic appearing marrow.

Our case highlights a series of bone marrow biopsies from a patient with primary myelofibrosis. Over time, this patient developed an unusual fatty appearance to his marrow, confirmed on multiple biopsies. This finding was supported by a quantitative fat MRI sequence that also shows a fatty appearance to the marrow.

Unexpected disseminated histoplasmosis detected by bone marrow biopsy in a solid organ transplant patient.

Disseminated histoplasmosis and hemophagocytic lymphohistiocytosis show overlapping features, which require careful contextual interpretation. Histopathologic evaluation can potentially rapidly identify cases of possible histoplasmosis. A high index of clinical suspicion, particularly in endemic areas and in a setting of immunosuppression, is critical to appropriate diagnosis and treatment.

Philadelphia Chromosome-like Mixed-Phenotype Acute Leukemia Demonstrating P2RY8-CRLF2 Fusion and JAK1 Mutation.

OBJECTIVES: Philadelphia chromosome-like (Ph-like) genetic alterations define a subset of B lymphoblastic leukemia/lymphoma (B-ALL), which represents a separate provisional entity in the World Health Organization 2016 updated classification. However, these alterations have not been described outside the context of B-ALL. METHODS: Cytogenomic array and molecular analysis identified a Ph-like signature in a mixed-phenotype acute leukemia (MPAL), B/myeloid, confirmed using conventional immunophenotypic and cytochemical analysis. RESULTS: Flow cytometry identified a blast population demonstrating a B-cell lineage and myeloperoxidase positivity. A P2RY8-CRLF2 fusion and JAK1 mutation were detected, both of which are associated with Ph-like features. CONCLUSIONS: To our knowledge, this is the first report of Ph-like MPAL, which may represent a new diagnostic entity. We emphasize the need for refinement of diagnostic criteria for MPALs and highlight an opportunity for expansion of inclusion criteria in ongoing clinical trials studying the use of tyrosine kinase inhibitor therapy to include cases of Ph-like MPAL.

Diagnostic and therapeutic implications of genetic heterogeneity in myeloid neoplasms uncovered by comprehensive mutational analysis.

While growing use of comprehensive mutational analysis has led to the discovery of innumerable genetic alterations associated with various myeloid neoplasms, the under-recognized phenomenon of genetic heterogeneity within such neoplasms creates a potential for diagnostic confusion. Here, we describe two cases where expanded mutational testing led to amendment of an initial diagnosis of chronic myelogenous leukemia with subsequent altered treatment of each patient. We demonstrate the power of comprehensive testing in ensuring appropriate classification of genetically heterogeneous neoplasms, and emphasize thoughtful analysis of molecular and genetic data as an essential component of diagnosis and management.

Unexpected TTF-1 Positivity in a Subset of Gastric Adenocarcinomas.

Thyroid transcription factor-1 (TTF-1) is traditionally used to identify tumors of lung and thyroid primary. However, the specificity of this marker has recently come under increasing scrutiny as tumors from other organ systems are shown to also stain positively for TTF-1. On the basis of an index case of TTF-1-positive gastric adenocarcinomas, we evaluated a retrospective cohort (n=91) of these tumors for TTF-1 staining. Archived paraffin-embedded blocks of gastric adenocarcinoma cases from 2008 to 2013 were chosen for immunohistochemical staining. We report unexpected TTF-1 positivity in up to 25% of cases using the most sensitive TTF-1 clone SPT24. A subset of these cases also shows concurrent Napsin A positivity, including a case with lymph node metastasis, highlighting the potential for diagnostic confusion when dealing with metastatic disease of unknown origin. Because TTF-1 is not detected in the vast majority of cases using a separate antibody clone, 8G7G3/1, we conclude that aberrant staining is due to cross-reactivity to unknown antigen(s). TTF-1 positivity and even Napsin A positivity, therefore, cannot be used as conclusive evidence of pulmonary origin and gastrointestinal origin must be considered in the differential diagnosis.

Insulin regulates adipocyte lipolysis via an Akt-independent signaling pathway.

After a meal, insulin suppresses lipolysis through the activation of its downstream kinase, Akt, resulting in the inhibition of protein kinase A (PKA), the main positive effector of lipolysis. During insulin resistance, this process is ineffective, leading to a characteristic dyslipidemia and the worsening of impaired insulin action and obesity. Here, we describe a noncanonical Akt-independent, phosphoinositide-3 kinase (PI3K)-dependent pathway that regulates adipocyte lipolysis using restricted subcellular signaling. This pathway selectively alters the PKA phosphorylation of its major lipid droplet-associated substrate, perilipin. In contrast, the phosphorylation of another PKA substrate, hormone-sensitive lipase (HSL), remains Akt dependent. Furthermore, insulin regulates total PKA activity in an Akt-dependent manner. These findings indicate that localized changes in insulin action are responsible for the differential phosphorylation of PKA substrates. Thus, we identify a pathway by which insulin regulates lipolysis through the spatially compartmentalized modulation of PKA.