Whole Genome and Exome Sequencing Defines The Genetic Landscape Of Hepatosplenic T-Cell Lymphoma

Background Hepatosplenic T-cell lymphoma (HSTL) is a rare form of lymphoma, comprising less than 1% of the cases. However, HSTL extracts a highly disproportionate toll on patients with a median age of diagnosis of 35 years and an expected median survival of less than two years. The vast majority of HSTL patients eventually succumb to their disease. The genetic basis of the disease is largely unknown. Although abnormalities of chromosome 7, including isochromosome 7q occur commonly in the disease, the role of specific genes and genetic mutations to the disease remains essentially unknown. Methods In this study, we sought to define the genetic features of HSTL through the whole genome sequencing and exome sequencing of 32 HSTL tumors and germline DNA (where available) from the same patients. Exome enrichment of DNA was carried out using the Agilent solution-based system of exon capture, which uses RNA baits to target all protein coding genes as well as ∼700 human microRNAs. Both whole genome and exome sequencing were performed using the Illumina platform. Results We identified 28 candidate cancer genes that were recurrently mutated in HSTL. Commonly implicated biological processes comprising these genes included signal transduction (e.g. PIK3CD, KRAS) and chromatin modification (e.g. TET1, SETD2 and MLL3), accounting for 16% and 23% of the total genetic events, respectively. Nearly all of these genes have been implicated in HSTL for the first time and provide new insights into the pathogenesis of the disease and potential targets for therapy. Whole genome sequencing confirmed isochromosome 7q as the most common recurrent chromosomal abnormality in HSTL and additional structural genetic alterations in chromosome 7. Conclusion Our study provides the most comprehensive genetic portrait of HSTL to date, and is a significant step in defining the genetic causes of this disease. Disclosures: No relevant conflicts of interest to declare.

Acquisition of Isochromosome 7 Is a Late Change in the Pathogenesis of Hepatosplenic Lymphoma, Documented On a Case of Adolescent Girl 5 Years After Renal Transplant with Preceding TCR Gamma-Delta Positive LGL Leukemia.

Abstract 5031 Background Post-transplant lymphoproliferative disorders (PTLD) occur in 1-20% of recipients receiving solid organ transplantation. We describe a patient who suffered from hepatosplenic T-cell lymphoma occurring after previous PTLD in a renal transplant recipient. Patient/Methods An 11-yr-old girl underwent kidney transplantation for end-stage Fanconi's nephronophthisis in 2002. In October 2006 significant neutropenia (<200/uL) was firstly detected, without any abnormality in bone marrow (BM) aspirate and without hepato- or splenomegaly. Episodes of neutropenia resolved spontaneously or after enhanced immunosuppression and G-CSF. In January 2007 new episodes of neutropenia and newly significant “monocytosis” were detected in peripheral blood (PB) and BM. Percentage of “monocytes” corresponded with immunophenotypically atypical TCR gamma/delta positive T cells (CD7weakposCD5negCD3bright) in PB and BM. Clonal TCR gamma and delta rearrangements were identified which enabled qPCR minimal residual disease (MRD) assessment. No lymphadenopathy was present, slight hepatosplenomegaly was identified by sonography. Conventional and molecular cytogenetic analyses didn't reveal any chromosomal aberration in PB and BM including changes on chromosome 7. No increased levels of EBV and CMV load by PCR were found. Partial increase of granulocytes and slight decrease of atypical TCR gamma/delta T cells were detected after administration of corticosteroid bolus and mercaptopurin. Three months later she presented with fever, rapidly progressive hepatosplenomegaly and pancytopenia, clinically corresponding with hepatosplenic lymphoma. At this time, newly acquired isochromosome 7q was detected by FISH. Results Initial therapy with campath and fludarabine was ineffective. She didn't respond to the 2nd line treatment (prednisone, vincristine, daunorubicine,asparaginase) and died 2 weeks later from lymphoma progression. Autopsy identified severe hemophagocytosis in the liver. Retrospectively, we identified identical clonal TCR rearrangements in the PB samples from March 2006 (∼0.03% of lymphoma PB MRD level), when neither changes in PB count nor clinical symptoms were found. Conclusion We detected a “pre-lymphoma” phase with clonal expansion of atypical TCR gamma/delta T cells more than 1 year before lymphoma manifestation. The presence of isochromosome 7q was a late change during this lymphoma genesis. Grant support IGA NS/9997-4; IGA NR/9531-3, IGA NS 10480-3, Research Projects MZCR 000064203, MSM0021620813 Disclosures No relevant conflicts of interest to declare.

Hepatosplenic γδ T-Cell Lymphoma Masquerading as T Cell Acute Lymphoblastic Leukemia

Hepatosplenic γδ T-Cell Lymphoma (HSTCL) is an uncommon type of Peripheral T cell lymphomas characterized by hepatosplenomegaly without significant lymphadenopathy, with clinically significant cytopenias, predominance in young adult males and an aggressive clinical course. HSTCL have a characteristic immunophenotype CD2+, CD3+, CD4−, CD5−, CD7+, CD8-, TCRγδ+ and are associated with isochromosome 7q cytogenetic abnormality. The predominant laboratory findings are reduced peripheral blood cells ranging from isolated reduction of one lineage to pancytopenia. Lymphocytosis is usually uncommon at the point of diagnosis; however tumor cells may be commonly seen in blood. Two subpopulations of atypical cells are seen – small sized cells with irregular nuclear margins and the medium to large size cells which often resemble blasts. The blast like cells are known to increase with disease progression and a complete blastic transformation though known has been mostly reported in the terminal phase of the disease. We present three cases of HSTCL, all of which presented with lymphocytosis and increased blast like cells (17%–91%) at diagnosis. These cases included two females and one male in an age group of 13– 17 years. They all presented with generalized systemic complaints, bleeding symptoms and on examination had pedal edema, facial puffiness and moderate to marked hepatosplenomegaly. Immunophenotyping performed on peripheral blood sample using a limited primary panel of antibodies showed a common phenotype: surface CD3+, CD4−, CD8−, CD7+ & CD34−. In addition CD2 and CD5 were positive in two cases, CD56 was positive in one case while CD16 was negative in all three cases. Based on the blast like morphology of tumor cells and an aberrant T cell phenotype, all three cases were initially labeled as T cell Acute Lymphoblastic Leukemia (T-ALL) and treated as per the T-ALL treatment protocol of our institute. However they did not respond to treatment. These cases were reviewed in detail and a repeat Immunophenotypic analysis was done using a more elaborate panel. In addition to the initial Immunophenotypic markers, all three cases were positive for Surface TCR γδ and negative for Tdt. Hence a diagnosis of HSTCL was arrived at. Cytogenetically only one case showed the characteristic finding of isochromosome 7q. The diagnosis of HSTCL was not considered initially because of the blast like morphology of tumor cells and as surface TCR αβ/γδ is not part of our primary antibody panel. In addition in one case, cytoplasmic CD3 was interpreted as positive without taking into account surface CD3 positivity. This case series highlights the importance of using a comprehensive antibody panel for the diagnosis of hematolymphoid neoplasms including cytoplasmic markers and Tdt. It re-establishes the importance of assessing cytoplasmic positivity only after the surface positivity has been looked for. Aberrant surface CD3 expression and cytoplasmic γδ positivity is well known in T-ALL and a few cases of Tdt negative T-ALL are also known. However to the best of our knowledge there are no published reports of T-ALL expressing surface TCR γδ and in comparison HSTCL though surface CD3 positive, are Tdt negative. We suggest that in all such cases which are surface CD3 positive, CD34 negative and Tdt negative, Surface TCR γδ should be looked for and if found to be positive a diagnosis of HSTCL can be arrived at in the correct clinical setting. In conclusion, it is important to be aware of this rare entity of HSTCL presenting with leucocytosis & blast like cells and to differentiate it from T-ALL, as these two entities have different treatment and prognosis.

Hepatosplenic αβ T-Cell Lymphoma: A Report of an S100-Positive Case

Hepatosplenic T-cell lymphoma is an uncommon neoplasm characterized by a lymphoid infiltrate within the sinusoids of the liver, spleen, and bone marrow, without significant nodal involvement. The majority of cases express the γδ T-cell receptor and are associated with an isochromosome 7q cytogenetic abnormality. Recently, a small number of cases have been reported that express the αβ T-cell receptor. Here, we report our findings of a case of an S100-positive hepatosplenic αβ T-cell lymphoma in a 20-year-old woman who presented with pancytopenia and hepatosplenomegaly. The case adds to the growing literature of hepatosplenic αβ T-cell lymphomas.