Primary Low-Grade B-Cell Lymphoma of Skull With Translocation Between Immunoglobulin and Interferon Regulatory Factor 4 Genes.

Low-grade B-cell lymphoma with immunoglobulin (IG) and interferon regulatory factor 4 (IRF4) gene rearrangement is extremely rare, with only 4 cases being previously reported. In this article, we report one additional case that arises from the skull and review the literature. The patient was a 69-year-old man who presented with recurrent and disabling vertigo and was found to have a 5.0 × 1.7 cm lesion within the left posterior parietal bone. Histological examination revealed a bone lesion with diffuse lymphoid infiltrate comprising of mostly small lymphocytes with scant cytoplasm, slightly irregular nuclei and inconspicuous nucleoli, and scattered larger cells resembling prolymphocytes and paraimmunoblasts. Immunohistochemical studies showed that the neoplastic cells were positive for CD20, CD79a, PAX5, CD23, CD43, BCL-2, BCL-6, MUM-1, LEF-1, and IgM and negative for CD5, CD10, cyclinD1, SOX11, and IgD. Flow cytometric analysis identified CD5 negative and CD10 negative monoclonal B cells with lambda light chain restriction. Fluorescence in situ hybridization analysis revealed del(13q) abnormality, but was negative for IGH/BCL2, IGH/CCND1, and BIRC3/MALT1 translocations. Next-generation sequencing identified IGK-IRF4 rearrangement and BRD4 E1113 del abnormalities. Given a low clinical stage (IE) of the disease, the patient did not receive additional treatments and was free of disease at 1 year after the diagnosis.

Classical Hodgkin Lymphoma With Aberrant CD8 Expression: A Clinicopathologic Study of Five Cases.

Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (CHL) are of B-cell origin. In a small number of CHL cases, the tumor cells can express T-cell antigens. CD8 expression in this setting is extremely rare. We identified 5 cases of CHL with aberrant CD8 expression from our database. The patients included 3 men and 2 women with a median age of 33 years (range = 20-59 years). All the patients initially presented with lymphadenopathy and variable number of RS cells. Two cases were classified as mixed cellularity type that showed prominent vascular proliferation mimicking peripheral T-cell lymphoma. Two cases represented nodular sclerosis type. The tumor cells in all cases were positive for CD8 and negative for CD2, CD3, CD4, and CD7 and carried germline T-cell receptor genes. Molecular studies revealed T-cell receptor genes to be in germline configuration in 4 cases with available information. Given the morphologic overlap with peripheral T-cell lymphoma and the rarity of this type of CHL, identifying more cases will help our better understanding of this entity.

Primary Central Nervous System T-Cell Lymphoma With Aberrant Expression of CD20 and CD79a: A Diagnostic Pitfall.

Primary central nervous system T-cell lymphoma (PCNSTCL) is rare, accounting for 2% of CNS lymphomas. We report the first case of PCNSTCL with aberrant expression of CD20 and CD79a in an 81-year-old man with a left periventricular brain mass. A biopsy revealed dense lymphoid infiltrate consisting of medium-sized cells in a background of gliosis and many histiocytes. The lymphoid cells were positive for CD2, CD3, CD7, CD8, T-cell intracellular antigen-1, granzyme B, CD20, and CD79a and negative for CD4, CD5, PAX-5, OCT-2, BOB-1, human herpes virus-8, and Epstein-Barr virus-encoded small RNAs. Molecular studies revealed clonal TCR-ß and TCR-γ gene rearrangements and negative immunoglobulin gene rearrangements. The patient was treated with chemotherapy (vincristine and methotrexate) and rituximab, but he died 1 month after the diagnosis. This is a unique case that emphasizes the use of a multimodal approach, including a broad immunohistochemical panel and molecular studies in lineage determination for lymphomas with ambiguous phenotype.

Is Low Positive JAK2 V617F Mutation Test Result Clinically Significant?: Multi-Institutional Study.

OBJECTIVES: Acquired somatic mutation Janus kinase 2 (JAK2) V617F is associated with various myeloproliferative neoplasms (MPN). Allele-specific real-time polymerase chain reaction has been widely adopted to detect mutation; however, the utility of low positive results is not well understood. The aim of this study is to investigate the clinical significance of low positivity of JAK2 V617F. MATERIALS AND METHODS: Retrospective analysis was performed for JAK2 V617F mutation tests performed using JAK2 MutaQuant kit (Ipsogen) in molecular laboratories at 2 major academic medical centers between 2010 and 2012. Cases with low positive JAK2 V617F, defined as 0.2% to 5% mutant allele, were documented. Chart review was performed for the clinical correlation. RESULTS: A total of 1697 JAK2 V617F tests was performed. Forty-five cases (2.65%) yielded a low JAK2 V617F positivity (average 1.45%), the majority of which (n=26, 62%) had <1%. Eight cases had a history of MPN. The remaining cases were related to reactive conditions without a clonal disease. Our data indicate that a low positivity of JAK2 V617F can be seen in MPN as well as reactive conditions. CONCLUSIONS: An interpretation of JAK2 V617F status should not be performed simply following some arbitrary cutoff. Any low positivity of JAK2 V617F should be reported and a correlation with clinical information is warranted for proper interpretation.

Lymphoproliferative disorder that resembles heptosplenic lymphoma during maintenance treatment for T-cell acute lymphoblastic leukemia.

A 6-year-old male presented with a testicular mass, hepatosplenomegaly, and a pleural effusion while undergoing maintenance chemotherapy for treatment of T-cell acute lymphoblastic leukemia (T-ALL). He was subsequently diagnosed with a lymphoproliferative disorder that resembled hepatosplenic lymphoma (HSL). While the extranodal presentation and the protracted yet aggressive clinical course are consistent with HSL, the findings of monosomy 8 and polymorphic cell populations are unique and have not been previously described in this type of lymphoma.