Pathology and genetics of anaplastic large cell lymphoma.

Anaplastic large cell lymphomas are a rare subtype of peripheral/mature T-cell lymphomas which are clinically, pathologically and genetically heterogeneous. Both ALK-positive (ALK+) and ALK-negative (ALK-) ALCL are composed of large lymphoid cells with abundant cytoplasm and pleomorphic features with horseshoe-shaped and reniform nuclei. ALK+ ALCL were considered as a definite entity in the 2008 World Health Organization classification of hematopoietic and lymphoid tissues. ALK-ALCL was included as a provisional entity in the WHO 2008 edition and in the most recent 2017 edition, it is now considered a distinct entity that includes cytogenetic subsets that appear to have prognostic implications (e.g. 6p25 rearrangements at IRF4/DUSP22 locus). ALK+ ALCLs are distinct in epidemiology and pathogenetic origin and should be distinguished from ALK-ALCL, cutaneous ALCL and breast implant associated ALCL which have distinct clinical course and pathogenetic features. Breast implant-associated ALCL is now recognized as a new provisional entity distinct from other ALK-ALCL; notably that it is a noninvasive disease associated with excellent outcome. In this article, we will provide an overview of the salient themes relevant to the pathology and genetic mechanisms in ALCL.

Two-year-old female with EBV-positive diffuse large B-cell lymphoma and subsequent CNS involvement with neurolymphomatosis.

We describe a case of Epstein-Barr virus (EBV) positive, diffuse large B-cell lymphoma in a 2-year-old female who went on to develop relapsed/refractory central nervous system (CNS) disease, manifesting as cranial nerve neurolymphomatosis. Although her atypical presentation was thought to be associated with an immune deficiency, extensive work-up was negative. Despite subsequent treatment with third-party EBV-specific cytotoxic T-lymphocytes, she died of progressive disease. This case report raises questions as to whether tailored treatment approaches should be considered for atypical presentations of pediatric lymphoma (e.g., CNS and virus-associated).

The oncogenic JUNB/CD30 axis contributes to cell cycle deregulation in ALK+ anaplastic large cell lymphoma.

Anaplastic lymphoma kinase (ALK)+ anaplastic large cell lymphoma (ALCL) frequently carries the t(2;5)(p23;q35) resulting in expression of NPM1(NPM)-ALK oncogenic kinase. The latter is capable of activating ERK kinase, which upregulates JUNB expression through ETS1. JUNB, in turn, interacts with the TNFRSF8 (CD30) gene promoter and induces CD30 (TNFRSF8) overexpression. However, the role of CD30 overexpression in ALK+ ALCL oncogenesis remains unknown. Here we show that the JUNB gene is frequently amplified in ALK+ ALCL, suggesting gene amplification as an additional underlying mechanism for JUNB overexpression. Silencing of JUNB resulted in reduced cell growth and colony formation associated with decreased activator protein-1 activity and G1/S and G2/M cell cycle arrest. These effects were linked to decreased CD30 levels, downregulation of CCNA2 (Cyclin A), CCND2 (Cyclin D2) and CCND3 (Cyclin D3) and upregulation of cyclin-dependent kinase inhibitors CDKN2A (p14) and CDKN1A (p21), but not CDKN1B (p27). Similar cell cycle changes were observed following the knock-down of TNFRSF8 gene or blockade of its function using anti-CD30 antibodies, which were associated with upregulation of CDKN2A and CDKN1A, but not CDKN1B. These findings indicate that JUNB may partly operate through CD30 signalling. Silencing of JUNB also sensitized NPM1-ALCL+ cells to standard chemotherapeutic agents. Our findings uncover the oncogenic role of the JUNB/CD30 axis and its potential as therapeutic target in ALK+ ALCL.

Comprehensive genomic analysis reveals molecular heterogeneity in pediatric ALK-positive anaplastic large cell lymphoma.

Anaplastic large cell lymphoma (ALCL) is a mature T-cell lymphoma that accounts for for 10-15% of childhood lymphomas. Despite the observation that more than 90% of pediatric cases harbor the anaplastic lymphoma kinase (ALK) rearrangement resulting in aberrant ALK kinase expression, there is significant clinical, morphologic, and biological heterogeneity. To gain insights into the genomic aberrations and molecular heterogeneity within ALK-positive ALCL(ALK+ ALCL), we analyzed 46 pediatric ALK+ ALCLs by whole-exome sequencing, RNA-sequencing, and DNA methylation profiling. Whole-exome sequencing found on average 25 SNV/Indel events per sample with recurring genetic events in regulators of DNA damage (TP53, MDM4), transcription (JUNB), and epigenetic regulators (TET1, KMT2B, KMT2A, KMT2C, KMT2E). Gene expression and methylation profiling consistently subclassified ALK+ ALCLs into two groups characterized by diferential ALK expression levels. The ALK-low group showed enrichment of pathways associated with immune response, cytokine signaling, and a hypermethylated predominant pattern compared to the ALK- high group, which had more frequent copy number changes, and was enriched with pathways associated with cell growth, proliferation, metabolic pathways, and. Taken together, these findings suggest that there is molecular heterogeneity within pediatric ALK+ALCL, predicting distinct biological mechanisms that may provide novel insights into disease pathogenesis and represent prognostic markers.

Functional inhibition of BCL2 is needed to increase the susceptibility to apoptosis to SMO inhibitors in diffuse large B-cell lymphoma of germinal center subtype.

Previously, we have demonstrated that inhibition of Hedgehog pathway induces predominantly apoptosis in diffuse large B-cell lymphoma (DLBCL) cell lines of activated B-cell (ABC) type but predominantly cell cycle arrest in those of germinal center (GC). Here, we explored the possibility of overcoming the resistance to apoptosis to SMO inhibitors in five DLBCL cells of GC type using the combination of the SMO inhibitor HhAntag (Genentech Inc) with the BH3 mimetic ABT-737 (Abbott Laboratories). As controls we have used two DLBCL of ABC type (OCI-LY10 and OCI-LY3). Combinatorial treatments were performed with increasing concentrations of the HhAntag with low doses (equal or less than the IC20) of ABT-737. MTS assays were used to detect changes in cell viability and Annexin-V and PARP1 cleavage assays were used to detect apoptosis. Combining low doses of ABT-737 with increasing concentrations of HhAntag in GC DLBCL cell lines resulted in significantly increase of apoptosis in comparison to treatments with the SMO inhibitor alone. We concluded that in GC DLBCL cell lines, in contrast to those of ABC type, functional inhibition of BCL2 family members is usually needed to overcome the resistance to apoptosis to SMO inhibitors. These findings provide a rationale to explore the use of SMO and BCL2 inhibitors as adjuvant therapy for treatment of DLBCL of GC type.

Malignant Progression of an Ancestral Bone Marrow Clone Harboring a CIC-NUTM2A Fusion in Isolated Myeloid Sarcoma.

Myeloid sarcoma is a rare condition consisting of extramedullary myeloid blasts found in association with acute myeloid leukemia or, in the absence of bone marrow involvement. We identified an infant with isolated myeloid sarcoma whose bone marrow was negative for involvement by flow cytometry. Sequencing revealed the fusion oncogene CIC-NUTM2A and identified the sarcoma to be clonally evolved from the bone marrow, which carried the fusion despite the absence of pathology. Murine modeling confirmed the ability of the fusion to transform hematopoietic cells and identified receptor tyrosine kinase (RTK) signaling activation consistent with disruption of the CIC transcriptional repressor. These findings extend the definition of CIC-rearranged malignancies to include hematologic disease, provide insight into the mechanism of oncogenesis, and demonstrate the importance of molecular analysis and tracking of bone marrow involvement over the course of treatment in myeloid sarcoma, including patients that lack flow cytometric evidence of leukemia at diagnosis. IMPLICATIONS: This study illustrates molecular involvement of phenotypically normal bone marrow in myeloid sarcoma, which has significant implications in clinical care. Further, it extends the definition of CIC-rearrangements to include hematologic malignancies and shows evidence of RTK activation that may be exploited therapeutically in cancer(s) driven by these fusions.

TP53 pathway analysis in paediatric Burkitt lymphoma reveals increased MDM4 expression as the only TP53 pathway abnormality detected in a subset of cases.

The TP53 (p53) pathway can be inhibited by TP53 mutation or deletion or by MDM2 overexpression. Both occur in Burkitt lymphoma (BL), but many cases lack either abnormality. Expression patterns of the TP53 inhibitor MDM4 have not been reported in BL, and increased MDM4 could deregulate the TP53 pathway in cases without TP53 or MDM2 abnormalities. We investigated TP53 pathway disruption in paediatric BL patient samples (n = 30) by studying MDM4, MDM2, and CDKN1A (p21) protein and mRNA expression; TP53 mutations; TP53 protein expression; and gene copy number abnormalities. MDM4 protein was expressed in 30/30 tumours, and MDM2 protein was weakly expressed in 7/30 (23%). All cases were negative for CDKN1A protein, and CDKN1A mRNA levels were decreased. TP53 mutations were detected in 5/28 (18%) cases and confirmed by sequencing. TP53 protein was expressed in 15/30 (50%) cases, including 7/8 with TP53 genetic alterations. MDM2 protein and mRNA expression levels did not correlate with lack of TP53 genetic changes or TP53 protein expression; however, there was an inverse relationship between detectable TP53 protein expression and MDM4 copy number gains and mRNA expression. The TP53 pathway is deregulated in paediatric BL cases, and increased MDM4 expression may be the primary mechanism in some cases.

Expression patterns of endothelin-1 and its receptors in colorectal cancer.

BACKGROUND AND OBJECTIVES: Endothelin-1 (ET-1), a potent vasoconstricting peptide, plays an important role in carcinogenesis. Previous in vitro studies have shown that colorectal cancer cells produce ET-1. METHODS: ET-1 and its receptors ET-A (ET(A) R) and ET-B (ET(B) R) were analyzed in colorectal cancer cell lines and tumors by Western blot and immunohistochemistry. Also, ET-1 levels were measured by ELISA in blood samples collected before and after tumor resection. RESULTS: ET-1 was immunohistochemically expressed by tumor cells at a variable level in 39 cases tested. The adjacent normal mucosa was negative for ET-1 expression. Strong ET(A) R expression observed in the deeper infiltrating areas at the periphery of neoplastic tissue correlated significantly with tumor stage. ET(B) R levels were very low or undetectable. Western blot analysis in paired (normal, tumor) fresh-frozen samples of colorectal cancers and in four colon carcinoma cell lines confirmed these findings. In addition, lower levels of ET-1 in the peripheral circulation after the tumor resection were found by ELISA as compared to those observed before surgery. CONCLUSIONS: ET-1 and ET(A) R, but not ET(B) R, are expressed at a higher level in primary and cultured colon carcinoma cells as compared to normal colon mucosa cells. Further functional studies are needed to explore the role of ET-1/ET(A) R axis in colon carcinogenesis.

Extracavitary/solid variant of primary effusion lymphoma.

Primary effusion lymphoma (PEL) is a distinct clinicopathologic entity associated with human herpesvirus 8 (HHV8) infection that mostly affects patients with immunodeficiency. Primary effusion lymphoma usually presents as a malignant effusion involving the pleural, peritoneal, and/or pericardial cavities without a tumor mass. Rare cases of HHV8-positive lymphoma with features similar to PEL can present as tumor masses in the absence of cavity effusions and are considered to represent an extracavitary or solid variant of PEL. Here, we report 3 cases of extracavitary PEL arising in human immunodeficiency virus-infected men. Two patients had lymphadenopathy and underwent lymph node biopsy. One patient had a mass involving the ileum and ascending colon. In lymph nodes, the tumor was predominantly sinusoidal. The tumor involving the ileum and ascending colon presented as 2 masses, 12.5 × 10.6 × 2.6 cm in the colon and 3.6 × 2.7 × 1.9 cm in the ileum. In each case, the neoplasms were composed of large anaplastic cells, and 2 cases had "hallmark cells." Immunohistochemistry showed that all cases were positive for HHV8 and CD138. One case also expressed CD4 and CD30, and 1 case was positive for Epstein-Barr virus-encoded RNA. Evidence of B-cell differentiation was poorly developed in all tumors. These cases highlight the importance of assessing HHV8 in an anaplastic tumor that arises in a human immunodeficiency virus-positive patient and further contributes to the limited literature currently available for extracavitary PEL.

A complex KMT2A::AFF3 fusion resulting from a three-way chromosomal rearrangement in pediatric B lymphoblastic leukemia.

The KMT2A::AFF3 fusion, t(2;11)(q11.2;q23.2), is a very rare fusion occurring in pediatric B-cell acute lymphoblastic leukemia (B-ALL). Our patient is a 2-year-old male who presented with three weeks of intermittent fever. Bone marrow biopsy showed 82% blasts and cytogenetic analysis demonstrated a complex 3-way chromosomal rearrangement involving KMT2A and an unknown fusion partner. Molecular testing identified the fusion partner as AFF3, a FLT3-TKD non-D835 mutation, and an NF1 mutation. This case demonstrates a highly complex three-way variant translocation resulting in the rare KMT2A::AFF3 fusion with only a few cases previously described in the literature.

It Takes a Village: Providing International Pediatric Pathology Services in a Resource-Limited Setting

OBJECTIVES: Partnerships between low- to middle-income countries (LMICs) and high-income countries (HICs) is one strategy to mitigate observed health disparities. Cambodia's Angkor Hospital for Children (AHC), an LMIC institution, faces shortages in health care resources, including pathology services. A partnership was created with Children's Wisconsin (CW), an HIC hospital, including provision of pathology services. We describe our established pathology workflow, examine cases seen in AHC patients, and evaluate the impact of CW's interpretations. METHODS: AHC provides clinical history and impression and ships samples to CW, which processes the samples, and pathologists provide interpretations, sending reports electronically to AHC. For analysis, final diagnoses were considered "concordant," "refined," or "discordant" based on agreement with the clinical impression. Cases were also classified as "did not change management" or "changed management" based on how CW interpretation affected clinical management. RESULTS: We included 347 specimens (177 malignant, 146 benign, 24 insufficient for diagnosis). Of these cases, 31% were discordant and 44% of cases with clinical follow-up had a change in management with CW interpretation. CONCLUSIONS: Inclusion of pathology services in LMIC-HIC partnerships is crucial for resolving health disparities between the institutions involved. The described partnership and established pathology workflow can be adapted to the needs and resources of many institutions.

Case Report: The First Case Report of Visceral Leishmaniasis in Cambodia.

Leishmaniasis is considered a neglected tropical disease that is commonly found in Asia, Africa, South America, and Mediterranean countries. Visceral leishmaniasis (VL) is the most severe form of the disease and is almost universally fatal if left untreated. The symptoms of VL overlap with many infectious diseases, malignancies, and other blood disorders. The most common findings include fever, cytopenias, and splenomegaly. Given the nonspecific symptoms, the diagnosis requires detailed laboratory investigations, including bone marrow examination, that can be challenging in low- and middle-income countries. Diagnostic limitations likely lead to the underdiagnosis or delay in diagnosis of VL. We describe, to our knowledge, the first case report of VL in Cambodia in a child presenting with fever, anemia, and thrombocytopenia. The diagnosis required a liver biopsy and multiple bone marrow biopsies to visualize intracellular Leishmania spp. Our case illustrates the diagnostic challenges and the importance of timely diagnosis. This case also highlights the need for heightened awareness of the diagnostic findings of VL and improved reporting of tropical diseases.

ALK+ Anaplastic Large Cell Lymphoma (ALCL)-Derived Exosomes Carry ALK Signaling Proteins and Interact with Tumor Microenvironment.

The oncogenic pathways activated by the NPM-ALK chimeric kinase of ALK+ anaplastic large cell lymphoma (ALCL) are well characterized; however, the potential interactions of ALK signaling with the microenvironment are not yet known. Here we report that ALK+ ALCL-derived exosomes contain critical components of ALK signaling as well as CD30, and that exosome uptake by lymphoid cells led to increased proliferation and expression of critical antiapoptotic proteins by the recipient cells. The bone marrow fibroblasts highly uptake ALK+ ALCL-derived exosomes and acquire a cancer-associated fibroblast (CAF) phenotype. Moreover, exosome-mediated activation of stromal cells altered the cytokine profile of the microenvironment. These interactions may contribute to tumor aggressiveness and possibly resistance to treatment.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms.

We herein present an overview of the upcoming 5th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.