Bachir Alobeid

Stages of germinal center transit are defined by B cell transcription factor coexpression and relative abundance.

The transit of T cell-activated B cells through the germinal center (GC) is controlled by sequential activation and repression of key transcription factors, executing the pre- and post-GC B cell program. B cell lymphoma (BCL) 6 and IFN regulatory factor (IRF) 8 are necessary for GC formation and for its molecular activity in Pax5+PU.1+ B cells. IRF4, which is highly expressed in BCL6− GC B cells, is necessary for class switch recombination and the plasma cell differentiation at exit from the GC. In this study, we show at the single-cell level broad coexpression of IRF4 with BCL6, Pax5, IRF8, and PU.1 in pre- and post-GC B cells in human and mouse. IRF4 is down-regulated in BCL6+ human GC founder cells (IgD+CD38+), is absent in GC centroblasts, and is re-expressed in positive regulatory domain 1-positive centrocytes, which are negative for all the B cell transcription factors. Activated (CD30+) and activation-induced cytidine deaminase-positive extrafollicular blasts coexpress Pax5 and IRF4. PU.1-negative plasma cells and CD30+ blasts uniquely display the conformational epitope of IRF4 recognized by the MUM1 Ab, an epitope that is absent from any other IRF4+PU.1+ lymphoid and hemopoietic subsets. Low grade B cell lymphomas, representing the malignant counterpart of pre- and post-GC B cells, accordingly express IRF4. However, a fraction of BCL6+ diffuse large B cell lymphomas express IRF4 bearing the MUM1 epitope, indicative of a posttranscriptional modification of IRF4 not seen in the normal counterpart.

PRDM1/Blimp-1 is expressed in human B-lymphocytes committed to the plasma cell lineage

PRDM1/Blimp‐1 (in human and mouse, respectively) has a central role in determining and shaping the secretory arm of mature B‐cell differentiation. In this study, a mouse monoclonal antibody that recognizes PRDM1 was used to detail its distribution in normal human lymphoid tissue and in lymphoid neoplasms that correspond to different stages of B‐cell differentiation. PRDM1 was expressed in germinal centre blasts that co‐express Pax5, CD19, CD20, and CD10, but not BCL6 or MTA‐3. Pax5 was downregulated and full plasma cell morphology and phenotype were acquired by PRDM1+, nuclear cREL−, pre‐plasma cells upon exit from the germinal centre. Activated extrafollicular B‐cells (CD30+, Pax5+) were largely PRDM1−. PRDM1 was also absent in tissue histiocytes and the majority of resting T‐cells and S‐100+ antigen‐presenting cells. PRDM1 and CD138 were expressed simultaneously in human lymphomas with plasma cell differentiation, but not in marginal zone lymphomas or chronic lymphocytic leukaemias. A minority of diffuse large B‐cell lymphomas expressed PRDM1 and Hodgkin lymphomas were largely PRDM1−. Infiltrating T‐cells in PRDM1− B‐cell lymphomas expressed PRDM1. In conclusion, PRDM1 staining is a reliable and informative assay to define plasma cell commitment and differentiation in human normal and neoplastic B‐cell lineages. Copyright

Targeted genomic sequencing of pediatric Burkitt lymphoma identifies recurrent alterations in antiapoptotic and chromatin-remodeling genes

To ascertain the genetic basis of pediatric Burkitt lymphoma (pBL), we performed clinical-grade next-generation sequencing of 182 cancer-related genes on 29 formalin-fixed, paraffin embedded primary pBL samples. Ninety percent of cases had at least one mutation or genetic alteration, most commonly involving MYC and TP53. EBV(-) cases were more likely than EBV(+) cases to have multiple mutations (P < .0001). Alterations in tumor-related genes not previously described in BL were identified. Truncating mutations in ARID1A, a member of the SWI/SNF nucleosome remodeling complex, were seen in 17% of cases. MCL1 pathway alterations were found in 22% of cases and confirmed in an expanded panel. Other clinically relevant genomic alterations were found in 20% of cases. Our data suggest the roles of MCL1 and ARID1A in BL pathogenesis and demonstrate that comprehensive genomic profiling may identify additional treatment options in refractory disease.

Eosinophil-rich CD30+ lymphoproliferative disorder of the oral mucosa. A form of "traumatic eosinophilic granuloma".

We describe 3 patients who had oral mucosal lesions with features of traumatic eosinophilic granuloma (TEG) and containing CD30+ atypical cells. In 1 patient, the oral lesion was followed by skin nodules. All lesions were evaluated histologically, by immunohistochemical analysis, and by polymerase chain reaction (PCR) analysis of the T-cell receptor (TCR)γ chain gene. All oral lesions were characterized by a dense and deeply infiltrative lymphoproliferation, showing epitheliotropism and massive eosinophilia. They contained atypical large lymphoid cells, which expressed T-cell markers and CD30. PCR analysis showed a monoclonal rearrangement of the TCRγchain gene in all lesions and, in 1 patient, the same rearrangement in the oral and cutaneous specimens. The lesions in these patients seem to be the oral counterpart of the spectrum of primary cutaneous CD30+ lymphoproliferative disorders and should be recognized as such to avoid a diagnosis of large T-cell lymphoma and possible consequent overtreatment. However, they represent only a subset among several others within the complex and heterogeneous category of disorders referred to as TEG.

T‐cell post‐transplantation lymphoproliferative disorders after cardiac transplantation: a single institutional experience

Post‐transplantation lymphoproliferative disorders (PTLDs) are a well‐recognized and potentially life‐threatening complication of solid organ transplantation. While the vast majority of PTLDs are B‐cell lymphoproliferations, T‐cell PTLDs are rarely seen. Among 898 patients receiving cardiac transplants between 1990 and 2003, 34 patients (3·8%) developed PTLDs with two (0·2%) T‐cell PTLDs, 31 (3·5%) B‐cell PTLDs and one (0·1%) natural killer cell PTLD. An additional three cases of T‐cell PTLD were identified among all cardiac transplant patients followed at our institution. These T‐cell PTLDs comprised a heterogeneous group of Epstein–Barr virus negative lymphoproliferations that developed late after transplantation and followed an aggressive course.

Aggressive presentation of breast implant-associated ALK-1 negative anaplastic large cell lymphoma with bilateral axillary lymph node involvement

We recently encountered a unique case of breast silicone implant-associated ALK-1 negative anaplastic large cell lymphoma (ALCL) in a female with a remote history of breast carcinoma, which presented as a sinusoidal infiltrate in an axillary lymph node (LN) and had a highly complex karyotype. A 68-year-old female had undergone right breast lumpectomy followed by right modified radical mastectomy with axillary LN dissection in 1991 for infiltrating moderately differentiated ductal carcinoma. No lymphovascular invasion or LN involvement was identified. She received six cycles of chemotherapy and 5 years of tamoxifen. In January of 1992, the patient underwent right breast reconstruction with a silicone implant. Sixteen years later the patient developed right axillary lymphadenopathy. Her past medical history was significant only for the prior breast carcinoma and biliary cirrhosis. She had no history of non-Hodgkin or Hodgkin lymphoma. Right axillary LN biopsy showed a large cell neoplasm infiltrating and expanding the sinuses (Figure1A). An exhaustive staining panel led to the diagnosis of an ALK-1 negative ALCL (Figure1B). A staging bone marrow biopsy showed no evidence of lymphoma. A subsequent FDG-PET/CT scan showed a hypermetabolic focus (maximum SUV 7.4) posterior to the breast implant. The grossly intact implant was removed with capsulectomy. Histologic review of the fibrotic capsular tissue showed an infiltrate of large neoplastic cells as seen previously (Figure 2A), which had the following phenotype (Figure 2B): CD457/þ, CD30þ, CD15þ, EMAþ, MUM1þ, CD2þ and CD4þ. These cells did not express CD3, CD5, CD7, CD8, ALK-1, CD56, CD20, PAX5, CD79a, OCT2, CD138, p53, or cytotoxic T-cell granule constituents (TIA-1, granzyme-B and perforin). In situ hybridisation for EBV mRNA was negative. The proliferation rate, as assessed with a stain for Ki-67, was 490%. Cytogenetic analysis revealed highly complex clonal chromosome abnormalities, penta-ploidy range metaphases and homogenously staining regions (hsr’s): 116–123,55N4,XX,71, add(1)(p36.3),i(1)(q10),hsr(1)(q21q25),þ2,þ362, þ6,hsr(7)(q32q35)62,i(8)(q10),þ9,þ10, inv(11) (p15.1q22.1)63,add(12)(q24.1),713,714,715,i (17)(q10),þ19,720,þ1*8mar[cp13]/46,XX,inv(11) (p15.1q22.1)[7]. FISH analysis using T-cell receptor alpha/delta break-apart, ALK break-apart and D7S486/CEP7 probes showed no evidence of rearrangement or deletion. PCR analysis showed clonal T-cell receptor beta gene rearrangement. Four months after initial diagnosis, the patient developed left-sided (contralateral) axillary lymphadenopathy, and a LN biopsy again disclosed sinusoidal infiltrates of ALCL. After completion of six

Hematogones: a review and update

Our knowledge regarding the nature and function of ‘hematogones’ has evolved considerably, since the initial description more than 70 years ago. Once considered the ‘mystery cells’ of the bone marrow, major advances in immunology and flow cytometry have enabled us to better characterize these cells and recognize them as physiologic precursors of B-cells. In this review, we describe the morphologic and phenotypic characteristics and clinical relevance of hematogones, and report recent advances in our understanding and knowledge of these cells as they relate to physiologic and different pathologic conditions.

FISH analysis in addition to G-band karyotyping: Utility in evaluation of myelodysplastic syndromes?

Cytogenetic analysis provides important diagnostic and prognostic information for patients with myelodysplastic syndromes (MDS). Prior studies, mostly comprised of small sample sizes, have reported conflicting results while evaluating the usefulness of FISH in addition to G-band karyotyping in MDS. In the current study, the utility of performing a tailored FISH panel, in addition to G-band karyotyping was evaluated in a series of 110 MDS patients diagnosed at our institute. Using our FISH panel, clonal cytogenetic abnormalities were detected in 3/8 (38%) of MDS cases with karyotype failure and in 5/54 (9%) cases with normal G-band karyotypes, all the latter had intermediate or high grade MDS. Of the cases with abnormal G-band karyotypes, 6/48 (13%) showed discrepancies between FISH and G-band results, however, FISH analysis only lead to reassignment of karyotypic abnormalities to different chromosomes, MDS cytogenetic risk stratification was not altered. Our findings suggest that FISH testing is informative only in MDS cases with karyotype failure and intermediate-high grade MDS cases with normal G-band karyotype and has limited utility in cases that have normal G-band karyotypes and morphologic features of low grade MDS or in cases with abnormal G-band karyotypes.

A critical analysis of prognostic factors in North American patients with human T-cell lymphotropic virus type-1-associated adult T-cell leukemia/lymphoma

To define the clinicopathologic and prognostic features of patients with human T‐cell lymphotropic virus type‐1 (HTLV‐1)‐associated adult T‐cell leukemia/lymphoma (ATLL) in North America, standard criteria were used to identify patients with ATLL.

Expression of inhibitory receptor ILT3 on neoplastic B cells is associated with lymphoid tissue involvement in chronic lymphocytic leukemia.

T cell responses against leukemia‐associated antigens have been reported in chronic lymphocytic leukemia (CLL). However, the relentless accumulation of CLL B cells in some patients indicates that anti‐tumor immune responses are inefficient. Inhibitory receptors from the Ig‐like transcript (ILT) family, such as ILT3 and ILT4, are crucial to the tolerogenic activity of antigen presenting cells. In this study, we examined the expression of ILT3 on CD5+ B cells obtained from 47 patients with CLL. Using flow cytometry and RT‐PCR, we found that B CLL cells from 23 of 47 patients expressed ILT3 protein and mature ILT3 mRNA. ILT3 protein and mRNA were not found in normal B cells obtained from donors without CLL. Expression of ILT4 in normal and B CLL cells showed a pattern similar to ILT3. The frequency of ILT3 positive CLL B cells was higher in patients with lymphoid tissue involvement, suggesting that ILT3 may have prognostic value in CLL. Our findings indicate that expression of ILT3 and ILT4 on CLL B cells represents a phenotypic abnormality that may play a role in tolerization of tumor‐specific T cells.