Bio

Clinical Focus


  • Hematopathology
  • Anatomic Pathology

Academic Appointments


Administrative Appointments


  • Associate Director, Stanford Society of Physician Scholars (2010 - 2012)
  • Member, College of American Pathologists (CAP) Cancer Biomarker Reporting Committee (CBRC) Hematopathology (2013 - Present)
  • Associate Member, Stanford Cancer Institute (2013 - Present)

Honors & Awards


  • Best Junior Faculty Teacher of Clinical Pathology, Stanford University (2014)
  • Research Scholar, College of American Pathologists (2012)

Professional Education


  • Board Certification: Hematology, American Board of Pathology
  • Residency:Stanford Hospital and Clinics (2012) CA
  • Fellowship:Stanford Hospital and Clinics (2011) CA
  • BA, Princeton, Molecular Biology (2000)
  • Medical Education:Harvard Medical School (2008) MA
  • Medical Education (HST), Massachusetts Institute of Technology, MA (2008)
  • PhD, Harvard, Cell and Developmental Biology (2006)
  • Board Certification, American Board of Pathology, Hematology (2012)
  • Board Certification, American Board of Pathology, Anatomic Pathology (2012)

Research & Scholarship

Current Research and Scholarly Interests


My research is focused on the pathologic classification and a mechanistic understanding of hematopoietic diseases; in recent years I have focused attention on T-cells, both neoplastic and reactive, and myeloid neoplasms in particular, using standard phenotyping as well as newer technologies. There are current research opportunities available for students, fellows and scholars.

Publications

Journal Articles


  • Mast Cells in Systemic Mastocytosis Have Distinctly Brighter CD45 Expression by Flow Cytometry AMERICAN JOURNAL OF CLINICAL PATHOLOGY Chisholm, K. M., Merker, J. D., Gotlib, J. R., Gitana, G., Lefterova, M., Zehnder, J. L., George, T. I., Arber, D. A., Ohgami, R. S. 2015; 143 (4): 527-534

    Abstract

    We sought to determine the significance of bright CD45 expression on mast cells in cases of systemic mastocytosis vs mast cells in bone marrows uninvolved by systemic mastocytosis and compare this CD45 expression with CD25 and CD2 expression on mast cells.Multiparameter flow cytometry was performed on 31 cases of systemic mastocytosis and 70 bone marrow cases that were not involved by systemic mastocytosis. Bright expression of CD45 was defined as more than 20% of CD117+ mast cells showing brighter CD45 expression than the average expression level of lymphocytes.Mast cells with bright CD45 expression were seen in 26 systemic mastocytosis cases and three bone marrows uninvolved by systemic mastocytosis (sensitivity, 84%; specificity, 96%). CD25 alone had a greater sensitivity (100%) but lower specificity (93%) compared with bright CD45 for identifying abnormal mast cells, while CD2 alone had lower sensitivity but higher specificity. To reach a specificity of 100%, CD25 together with bright CD45 on mast cells was the optimal combination to detect cases of systemic mastocytosis.A combination of bright CD45 and CD25 appears to specifically identify abnormal mast cells in cases of systemic mastocytosis. Further studies will be necessary to confirm these results.

    View details for DOI 10.1309/AJCPZ3J4GEEYIRRA

    View details for Web of Science ID 000351331200009

    View details for PubMedID 25780004

  • The diagnostic and clinical impact of genetics and epigenetics in acute myeloid leukemia. International journal of laboratory hematology Ohgami, R. S., Arber, D. A. 2015; 37 Suppl 1: 122-32

    Abstract

    Acute myeloid leukemia (AML) is a complex disease, for which our understanding of the role of genetic and epigenetic changes has undergone significant advancements. Newer diagnostic and prognostic classifications have increasingly incorporated such information, and novel therapies have been developed to target specific genes, processes, and pathways based on this growing understanding. Given the rapid evolution of this field, it is critical for physicians and translational researchers to have a more in-depth understanding of this evolving landscape. Here, we review both genetics and epigenetics in acute myeloid leukemia from a practical standpoint.

    View details for DOI 10.1111/ijlh.12367

    View details for PubMedID 25976970

  • Large B-Cell Lymphomas Poor in B Cells and Rich in PD-1+ T Cells Can Mimic T-Cell Lymphomas. American journal of clinical pathology Ohgami, R. S., Zhao, S., Natkunam, Y. 2014; 142 (2): 150-156

    Abstract

    To characterize the clinicopathologic features of cases of large B-cell lymphomas, poor in B cells and densely rich in programmed cell death-1 (PD-1)+ reactive T cells, which can mimic T-cell lymphomas.A single-institute retrospective review of cases between 2010 and 2013 was performed.Of 178 cases of large B-cell lymphomas, eight cases of large B-cell lymphomas poor in B cells and diffusely rich in sheets of PD-1+ T cells were identified. These cases either were initially misdiagnosed as a T-cell lymphoma or substantiated a broader differential diagnosis including a T-cell lymphoma. Five cases were T-cell histiocyte-rich large B-cell lymphomas, and three cases were diagnosed as large B-cell lymphomas rich in T cells. In three of these cases, a subset of the PD-1+ T cells showed either morphologic nuclear atypia or atypical expression of T-cell antigens on flow cytometry and/or immunohistochemistry.Large B-cell lymphomas poor in B cells and rich in T cells can have diffuse sheets of reactive PD-1+ T cells, some with atypical morphologic and immunophenotypic features mimicking a T-cell lymphoma. Careful assessment of the immunoarchitecture and background inflammatory and stromal cells can prevent erroneous diagnoses in such cases.

    View details for DOI 10.1309/AJCPFJWKQ6GTVQE6

    View details for PubMedID 25015854

  • STAT3 mutations are present in aggressive B-cell lymphomas including a subset of diffuse large B-cell lymphomas with CD30 expression. Haematologica Ohgami, R. S., Ma, L., Monabati, A., Zehnder, J. L., Arber, D. A. 2014; 99 (7)

    Abstract

    -

    View details for DOI 10.3324/haematol.2013.101543

    View details for PubMedID 24837465

  • E-Cadherin Is a Specific Marker for Erythroid Differentiation and Has Utility, in Combination With CD117 and CD34, for Enumerating Myeloblasts in Hematopoietic Neoplasms AMERICAN JOURNAL OF CLINICAL PATHOLOGY Ohgami, R. S., Chisholm, K. M., Ma, L., Arber, D. A. 2014; 141 (5): 656-664

    Abstract

    Objectives E-cadherin, epithelial calcium-dependent cell adhesion protein, has been identified as a marker of immature erythroid precursors in recent years. However, the specificity of E-cadherin in bone marrow specimens for erythroblasts vs myeloblasts or other early hematopoietic precursors in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) has not been fully elucidated. Methods We analyzed 105 cases of AML and MDS to evaluate the specificity of E-cadherin. Results Of 84 cases of AML, including cases with megakaryocytic, erythroid, monocytic, and granulocytic differentiation, all five acute erythroleukemia cases were positive, as well as one case of megakaryoblastic leukemia that showed coexpression of glycophorin A. In addition, we demonstrate that a panel of three markers, E-cadherin, CD117, and CD34, is effective in identifying lineage-specific myeloblasts in cases of MDS where left-shifted erythroid hyperplasia may complicate morphologic assessment of myeloblasts. Conclusions In marrow specimens, E-cadherin is a useful marker for erythroid differentation.

    View details for DOI 10.1309/AJCP8M4QQTAZPGRP

    View details for Web of Science ID 000335200400007

    View details for PubMedID 24713736

  • Next-generation sequencing of acute myeloid leukemia identifies the significance of TP53, U2AF1, ASXL1, and TET2 mutations. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc Ohgami, R. S., Ma, L., Merker, J. D., Gotlib, J. R., Schrijver, I., Zehnder, J. L., Arber, D. A. 2014

    Abstract

    We assessed the frequency and clinicopathologic significance of 19 genes currently identified as significantly mutated in myeloid neoplasms, RUNX1, ASXL1, TET2, CEBPA, IDH1, IDH2, DNMT3A, FLT3, NPM1, TP53, NRAS, EZH2, CBL, U2AF1, SF3B1, SRSF2, JAK2, CSF3R, and SETBP1, across 93 cases of acute myeloid leukemia (AML) using capture target enrichment and next-generation sequencing. Of these cases, 79% showed at least one nonsynonymous mutation, and cases of AML with recurrent genetic abnormalities showed a lower frequency of mutations versus AML with myelodysplasia-related changes (P<0.001). Mutational analysis further demonstrated that TP53 mutations are associated with complex karyotype AML, whereas ASXL1 and U2AF1 mutations are associated with AML with myelodysplasia-related changes. Furthermore, U2AF1 mutations were specifically associated with trilineage morphologic dysplasia. Univariate analysis demonstrated that U2AF1 and TP53 mutations are associated with absence of clinical remission, poor overall survival (OS), and poor disease-free survival (DFS; P<0.0001), whereas TET2 and ASXL1 mutations are associated with poor OS (P<0.03). In multivariate analysis, U2AF1 and TP53 mutations retained independent prognostic significance in OS and DFS, respectively. Our results demonstrate unique relationships between mutations in AML, clinicopathologic prognosis, subtype categorization, and morphologic dysplasia.Modern Pathology advance online publication, 21 November 2014; doi:10.1038/modpathol.2014.160.

    View details for DOI 10.1038/modpathol.2014.160

    View details for PubMedID 25412851

  • STAT3 mutations are frequent in CD30+ T-cell lymphomas and T-cell large granular lymphocytic leukemia. Leukemia Ohgami, R. S., Ma, L., Merker, J. D., Martinez, B., Zehnder, J. L., Arber, D. A. 2013; 27 (11): 2244-2247

    View details for DOI 10.1038/leu.2013.104

    View details for PubMedID 23563237

  • TdT(+) T-lymphoblastic Populations Are Increased in Castleman Disease, in Castleman Disease in Association With Follicular Dendritic Cell Tumors, and in Angioimmunoblastic T-cell Lymphoma AMERICAN JOURNAL OF SURGICAL PATHOLOGY Ohgami, R. S., Zhao, S., Ohgami, J. K., Leavitt, M. O., Zehnder, J. L., West, R. B., Arber, D. A., Natkunam, Y., Warnke, R. A. 2012; 36 (11): 1619-1628

    Abstract

    T-lymphoblastic lymphoma is an aggressive neoplasm requiring prompt clinical treatment. Conversely, indolent T-lymphoblastic proliferation mimics T-lymphoblastic lymphoma but consists of a proliferation of non-neoplastic TdT+ T cells, requiring no treatment. Recently, we identified several cases of indolent T-lymphoblastic proliferations in extrathymic lymphoid tissues: 1 in a patient suffering from Castleman disease (CD) associated with a follicular dendritic cell sarcoma/tumor, 1 in a patient with a history of angioimmunoblastic T-cell lymphoma (AITL), and 1 in association with acinic cell carcinoma. Interestingly, in the case of the patient with a history of AITL, these TdT+ T cells were seen in multiple anatomic sites over the span of 5 years. Here we review these 3 cases and extend our findings by demonstrating that TdT+ T-lymphoblastic populations are increased in lymph nodes of patients with CD (P=0.011), CD in association with follicular dendritic cell tumors, and AITL (P<0.01) compared with other T-cell or B-cell lymphomas or reactive lymph nodes. Finally, analysis of 352 nonhematolymphoid tumors including carcinomas, melanomas, and sarcomas demonstrates that TdT+ T cells are not increased in these tumors. Our studies not only present several detailed cases of indolent T-lymphoblastic proliferations, but also correlate these populations with specific hematologic diseases.

    View details for DOI 10.1097/PAS.0b013e318264e223

    View details for Web of Science ID 000310059600004

    View details for PubMedID 23060347

  • DNA methylation analysis of ALOX12 and GSTM1 in acute myeloid leukaemia identifies prognostically significant groups BRITISH JOURNAL OF HAEMATOLOGY Ohgami, R. S., Ma, L., Ren, L., Weinberg, O. K., Seetharam, M., Gotlib, J. R., Arber, D. A. 2012; 159 (2): 182-190

    Abstract

    To determine the role of DNA methylation in the progression of acute myeloid leukaemia (AML), we analysed the methylation status of ALOX12, GSTM1, HS3ST2 and FZD9 in 127 AML patients. Aberrant methylation of ALOX12 was associated with the subcategory AML with myelodysplasia-related changes (P = 0·0439) and specifically with megakaryocytic dysplasia (P = 0·0003). An association between HS3ST2 and AML patients with favourable cytogenetic risk was identified (P = 0·0469). In univariate and multivariate analysis, methylation of GSTM1 was associated with worse overall survival (OS) and disease-free survival (DFS), with hazard ratios of 2·57 and 1·86, respectively. Furthermore, the significance of methylation of GSTM1 in predicting poor prognosis was maintained within the subcategories of AML not otherwise specified (NOS), AML with intermediate cytogenetic risk and normal karyotype AML. Finally, patients with both GSTM1 and ALOX12 methylated, demonstrated worse outcomes when all AML patients were assessed (OS; P = 0·000411) as well as within AML NOS (DFS; P = 0·0023), AML with intermediate cytogenetic risk (OS; P = 0·0104) and normal karyotype AML (OS; P = 0·00636). This study implicates methylation of specific genes in the classification and prognostication of AML and suggests that the morphological feature of multilineage dysplasia may be a surrogate marker of gene methylation in at least a subset of AML cases.

    View details for DOI 10.1111/bjh.12029

    View details for Web of Science ID 000309242000009

    View details for PubMedID 22924777

  • Refining the diagnosis of T-cell large granular lymphocytic leukemia by combining distinct patterns of antigen expression with T-cell clonality studies LEUKEMIA Ohgami, R. S., Ohgami, J. K., Pereira, I. T., Gitana, G., Zehnder, J. L., Arber, D. A. 2011; 25 (9): 1439-1443

    Abstract

    T-cell large granular lymphocytic (LGL) leukemia is a complex diagnosis, requiring persistent clonal expansions of LGLs, and cytopenias. Often the diagnosis is unclear as non-clonal expansions of LGLs commonly occur in reactive conditions. To better understand T-LGL leukemia, we performed a comprehensive clinicopathologic analysis of 85 patients with LGL expansions. Interestingly, distinct CD8+(dim)/CD57+ populations, seen by flow cytometry, were significantly associated with clonal T-LGL leukemia (P < 0.001) as well as neutropenia (median absolute neutrophil count (ANC) 1.45 vs 3.19 × 10(9)/l; P = 0.0017). Furthermore, cases with distinct CD8+(dim)/CD57+ populations and monoclonal T cells had even lower ANCs (median ANC 1.41 × 10(9)/l; P = 0.001) compared with cases without these dual criteria. Additionally, complete or partial loss of CD5 expression was independently associated with clonal T-LGL leukemia (P<0.001) and neutropenia (median ANC 1.41 vs 2.70 × 10(9)/l; P = 0.002). This study describes specific immunophenotypic parameters to better define clonal cases of T-LGL leukemia associated with significant neutropenia.

    View details for DOI 10.1038/leu.2011.107

    View details for Web of Science ID 000294665400008

    View details for PubMedID 21617700

  • The utility of IgM, CD21, HGAL and LMO2 in the diagnosis of pediatric follicular lymphoma. Human pathology Karnik, T., Ozawa, M. G., Lefterova, M., Luna-Fineman, S., Alvarez, E., Link, M., Zehnder, J. L., Arber, D. A., Ohgami, R. S. 2015; 46 (4): 629-633

    Abstract

    Pediatric follicular lymphoma (pFL) is a rare neoplasm with features differing from follicular lymphoma arising in adults. Here, we describe a rare case of pFL that showed morphologic features partially overlapping with progressive transformation of germinal centers and reactive follicular hyperplasia. As typical of pFL, neoplastic B cells within follicles did not express B-cell leukemia/lymphoma 2 (BCL2). However, this case showed additional distinctive abnormal findings, which contributed to the diagnosis: (1) diffuse and uniform staining of immunoglobulin M (IgM) on cells within and outside of follicles, (2) abnormally dim expression of CD21 on follicular dendritic cells, and (3) expression of human germinal center-associated lymphoma (HGAL) and LIM domain only 2 (LMO2) on B cells in interfollicular and follicular areas. This case demonstrates the utility of these abnormal features, which can be seen in adult- or usual-type follicular lymphoma, in the diagnosis of pFL. Further studies are necessary to evaluate the significance of these findings in other cases of pFL.

    View details for DOI 10.1016/j.humpath.2014.12.016

    View details for PubMedID 25701230

  • Non-invasive monitoring of diffuse large B-cell lymphoma by immunoglobulin high-throughput sequencing. Blood Kurtz, D. M., Green, M. R., Bratman, S. V., Scherer, F., Liu, C. L., Kunder, C. A., Takahashi, K., Glover, C., Keane, C., Kihira, S., Visser, B., Callahan, J., Kong, K. A., Faham, M., Corbelli, K. S., Miklos, D., Advani, R. H., Levy, R., Hicks, R. J., Hertzberg, M., Ohgami, R. S., Gandhi, M. K., Diehn, M., Alizadeh, A. A. 2015

    Abstract

    Recent studies have shown limited utility of routine surveillance imaging for diffuse large B-cell lymphoma (DLBCL) patients achieving remission. Detection of molecular disease by immunoglobulin high-throughput sequencing (Ig-HTS) from peripheral blood provides an alternate strategy for surveillance. We prospectively evaluated the utility of Ig-HTS within 311 blood and 105 tumor samples from 75 patients with DLBCL, comparing Ig-HTS from the cellular (circulating leukocytes) and acellular (plasma cell-free DNA) compartments of peripheral blood to clinical outcomes and 18FDG PET/CT (n=173). Clonotypic immunoglobulin rearrangements were detected in 83% of patients with adequate tumor samples to enable subsequent monitoring in peripheral blood. Molecular disease measured from plasma, as compared to circulating leukocytes, was more abundant and more correlated with radiographic disease burden. Prior to treatment, molecular disease was detected in the plasma of 82% of patients compared to 71% in circulating cells (p=0.68). However, molecular disease was detected significantly more frequently in the plasma at time of relapse (100% vs. 30%; p = 0.001). Detection of molecular disease in the plasma often preceded PET/CT detection of relapse in patients initially achieving remission. During surveillance time-points prior to relapse, plasma Ig-HTS demonstrated improved specificity (100% vs. 56%, p<0.0001) and similar sensitivity (31% vs. 55%, p=0.4) compared to PET/CT. Given its high specificity, Ig-HTS from plasma has potential clinical utility for surveillance after complete remission.

    View details for DOI 10.1182/blood-2015-03-635169

    View details for PubMedID 25887775

  • Comprehensive genomic profiling identifies a novel TNKS2-PDGFRA fusion that defines a myeloid neoplasm with eosinophilia that responded dramatically to imatinib therapy. Blood cancer journal Chalmers, Z. R., Ali, S. M., Ohgami, R. S., Campregher, P. V., Frampton, G. M., Yelensky, R., Elvin, J. A., Palma, N. A., Erlich, R., Vergilio, J., Chmielecki, J., Ross, J. S., Stephens, P. J., Hermann, R., Miller, V. A., MILES, C. R. 2015; 5

    View details for DOI 10.1038/bcj.2014.95

    View details for PubMedID 25658984

  • Indolent T-lymphoblastic Proliferation With Disseminated Multinodal Involvement and Partial CD33 Expression. American journal of surgical pathology Ohgami, R. S., Sendamarai, A. K., Atwater, S. K., Liedtke, M., Fleming, M. D., Natkunam, Y., Warnke, R. A. 2014; 38 (9): 1298-1304

    Abstract

    Although indolent T-lymphoblastic proliferations (iT-LBP) are rare, this diagnosis should be excluded in any patient with an extrathymic proliferation of immature TdT+T cells. Unlike T-lymphoblastic leukemia/lymphoma, patients with iT-LBP do not require chemotherapy. We report a case of iT-LBP with disseminated multinodal involvement in an otherwise healthy 49-year-old woman. Multiple lymph node biopsies were performed over the course of several months demonstrating persistent and anatomically diffuse involvement. Over 18 months, and without therapy, she has remained healthy, and her lymphadenopathy significantly improved. No bone marrow or peripheral blood involvement was ever identified. Atypical T cells showed an immunophenotypic spectrum of T-cell antigen expression with partial CD33 on a subset of T cells detected by both flow cytometry and immunohistochemistry. Both T-cell clonality and Human Androgen Receptor Assay (HUMARA) studies, performed on lymph node biopsy specimens, were negative. This case represents the first detailed clinical, morphologic, molecular, and immunophenotypic description of disseminated multinodal involvement by nonclonal iT-LBP with partial CD33 expression on T cells.

    View details for DOI 10.1097/PAS.0000000000000197

    View details for PubMedID 24618611

  • Acute myeloid leukemia with monosomal karyotype: morphologic, immunophenotypic, and molecular findings. American journal of clinical pathology Weinberg, O. K., Ohgami, R. S., Ma, L., Seo, K., Ren, L., Gotlib, J. R., Seetharam, M., Cherry, A., Arber, D. A. 2014; 142 (2): 190-195

    Abstract

    Acute myeloid leukemia (AML) with monosomal karyotype (MK) recently has been reported to be associated with worse outcome than the traditional complex karyotype.In this retrospective study of 111 patients with AML, we identified 14 patients with MK (13% of all patients with AML) using the definition proposed by Breems et al.Five (36%) of these 14 patients had a loss of a single chromosome in the presence of other structural abnormalities, and nine (64%) had a loss of two or more autosomal chromosomes. Patients with AML-MK presented at an older age, with lower bone marrow blasts, and their blasts less frequently expressed CD34. Most patients with AML-MK had morphologic multilineage dysplasia and were predominantly subclassified as having AML with myelodysplasia-related changes (AML-MRC). Molecular analysis showed a significant absence of NPM1 and FLT3 in patients with AML-MK.Outcome data showed that patients with AML-MK had significantly worse overall survival, disease-free survival, and complete response compared with the rest of the patients with AML as well as within the AML-MRC group.

    View details for DOI 10.1309/AJCPMLO84JDNVLNK

    View details for PubMedID 25015859

  • Profound plasmacytosis in a patient with dengue. International journal of hematology Ewalt, M. D., Abeynayake, J., Waggoner, J. J., Pinsky, B. A., Ohgami, R. S. 2013; 98 (5): 518-519

    View details for DOI 10.1007/s12185-013-1452-3

    View details for PubMedID 24114365

  • Indolent T-Lymphoblastic Proliferation (iT-LBP): A Review of Clinical and Pathologic Features and Distinction from Malignant T-Lymphoblastic Lymphoma ADVANCES IN ANATOMIC PATHOLOGY Ohgami, R. S., Arber, D. A., Zehnder, J. L., Natkunam, Y., Warnke, R. A. 2013; 20 (3): 137-140

    Abstract

    In recent years, a new pathologic entity has emerged: indolent T-lymphoblastic proliferation (iT-LBP). iT-LBPs share immunophenotypic similarities with T-lymphoblastic lymphoma; however, T-lymphoblastic proliferations are clinically indolent, and unlike the malignant counterpart, these expansions of nonclonal terminal deoxynucleotidyl transferase (TdT)+ T cells do not require treatment. Here we review the clinical and pathologic features, which are required for an accurate diagnosis of an iT-LBP. We demonstrate specific criteria can be used to accurately diagnose iT-LBP, notably: (1) confluent groups of TdT+ T cells in a biopsy specimen, (2) relative preservation of surrounding normal lymphoid architecture, (3) TdT+ T cells without morphologic atypia, (4) absence of thymic epithelium, (5) nonclonal TdT+ T cells, (6) immunophenotype of developmentally normal immature thymic T cells, and (7) clinical evidence of indolence (follow-up >6 mo without progression).

    View details for DOI 10.1097/PAP.0b013e31828d17ec

    View details for Web of Science ID 000317588700001

  • Challenges in Consolidated Reporting of Hematopoietic Neoplasms Surgical Pathology Clinics Ohgami, R. S., Arber, D. A. 2013
  • The Efficacy of HGAL and LMO2 in the Separation of Lymphomas Derived From Small B Cells in Nodal and Extranodal Sites, Including the Bone Marrow AMERICAN JOURNAL OF CLINICAL PATHOLOGY Younes, S. F., Beck, A. H., Ohgami, R. S., Lossos, I. S., Levy, R., Warnke, R. A., Natkunam, Y. 2011; 135 (5): 697-708

    Abstract

    We studied the efficacy of 2 germinal center B-cell markers, HGAL and LMO2, in the separation of lymphomas derived from small B cells, particularly follicular lymphoma (FL) and marginal zone lymphoma occurring in nodal, extranodal, splenic, and bone marrow sites using immunohistochemical analysis for CD10, BCL6, BCL2, HGAL, and LMO2. Our results showed that HGAL and LMO2 are sensitive and specific markers for detecting FL in nodal and extranodal sites. In contrast, all markers were down-regulated in FL infiltrates in the bone marrow. CD10 and HGAL were expressed in a subset of FLs in the bone marrow and were highly correlated with each other and with CD21, a marker of follicular dendritic cells. We conclude that HGAL and LMO2 should be considered in immunohistochemical panels used for the routine workup of lymphomas derived from small B cells. In the bone marrow, staining for HGAL or CD10 can be helpful in making a diagnosis of FL, although they are absent in a subset of cases.

    View details for DOI 10.1309/AJCP7Z2BIBUNQPLZ

    View details for Web of Science ID 000289743400007

    View details for PubMedID 21502424

  • PAX8 expression reliably distinguishes pancreatic well-differentiated neuroendocrine tumors from Heal and pulmonary well-differentiated neuroendocrine tumors and pancreatic acinar cell carcinoma MODERN PATHOLOGY Sangoi, A. R., Ohgami, R. S., Pai, R. K., Beck, A. H., McKenney, J. K., Pai, R. K. 2011; 24 (3): 412-424

    Abstract

    PAX (paired box) genes encode a family of transcription factors that regulate organogenesis in a variety of organs. Very little is known about the role of PAX8 in endocrine cell development and the expression of PAX8 in neuroendocrine tumors. The purpose of this study was to analyze PAX8 immunohistochemical expression in gastroenteropancreatic and pulmonary well-differentiated neuroendocrine tumors to determine whether PAX8 can reliably distinguish pancreatic neuroendocrine tumors from neuroendocrine tumors of other anatomic sites and other pancreatic non-ductal neoplasms. In total, 221 well-differentiated neuroendocrine tumors were evaluated: 174 primary neuroendocrine tumors (66 pancreatic, 31 ileal, 21 pulmonary, 20 gastric, 17 rectal, 11 appendiceal, and 8 duodenal) and 47 neuroendocrine tumors metastatic to the liver (31 pancreatic, 11 ileal, 2 pulmonary, 2 duodenal, and 1 rectal). Fifteen solid-pseudopapillary neoplasms and six acinar cell carcinomas of the pancreas were also evaluated. PAX8 was positive in 49/66 (74%) primary pancreatic neuroendocrine tumors. PAX8 expression did not correlate with World Health Organization categorization, grade, size, functional status, or the presence of liver or lymph node metastasis. PAX8 expression was identified in 0/31 (0%) ileal, 0/21 (0%) pulmonary, 2/20 (10%) gastric, 5/17 (29%) rectal, 1/11 (9%) appendiceal, and 6/8 (75%) duodenal neuroendocrine tumors. PAX8 was positive in 4/15 (27%) solid-pseudopapillary neoplasms of the pancreas, whereas all acinar cell carcinomas (0/6) lacked immunoreactivity. Among liver metastases, only pancreatic neuroendocrine tumors (20/31, 65%) were PAX8 positive, whereas no cases of ileal (0/11), pulmonary (0/2), duodenal (0/2), and rectal (0/1) neuroendocrine tumor metastases were PAX8 positive. PAX8 is expressed in primary and metastatic pancreatic well-differentiated neuroendocrine tumors, and its expression can reliably distinguish pancreatic from ileal and pulmonary well-differentiated neuroendocrine tumors. Duodenal neuroendocrine tumors and a subset of rectal, gastric, and appendiceal neuroendocrine tumors may also express PAX8. PAX8 expression can distinguish pancreatic neuroendocrine tumors from acinar cell carcinomas, but its utility in distinguishing neuroendocrine tumors from solid-pseudopapillary neoplasms is limited.

    View details for DOI 10.1038/modpathol.2010.176

    View details for Web of Science ID 000287986600009

    View details for PubMedID 20890270

  • Diagnosing PNH in the era of FLAER Blood K, H., R, O. S., D, A. A., A, A., St, C. 2011; [e-letter]
  • Structure of the membrane proximal oxidoreductase domain of human Steap3, the dominant ferrireductase of the erythroid transferrin cycle PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Sendamarai, A. K., Ohgami, R. S., Fleming, M. D., Lawrence, C. M. 2008; 105 (21): 7410-7415

    Abstract

    The daily production of 200 billion erythrocytes requires 20 mg of iron, accounting for nearly 80% of the iron demand in humans. Thus, erythroid precursor cells possess an efficient mechanism for iron uptake in which iron loaded transferrin (Tf) binds to the transferrin receptor (TfR) at the cell surface. The Tf:TfR complex then enters the endosome via receptor-mediated endocytosis. Upon endosomal acidification, iron is released from Tf, reduced to Fe(2+) by Steap3, and transported across the endosomal membrane by divalent metal iron transporter 1. Steap3, the major ferrireductase in erythrocyte endosomes, is a member of a unique family of reductases. Steap3 is comprised of an N-terminal cytosolic oxidoreductase domain and a C-terminal heme-containing transmembrane domain. Cytosolic NADPH and a flavin are predicted cofactors, but the NADPH/flavin binding domain differs significantly from those in other eukaryotic reductases. Instead, Steap3 shows remarkable, although limited homology to FNO, an archaeal oxidoreductase. We have determined the crystal structure of the human Steap3 oxidoreductase domain in the absence and presence of NADPH. The structure reveals an FNO-like domain with an unexpected dimer interface and substrate binding sites that are well positioned to direct electron transfer from the cytosol to a heme moiety predicted to be fixed within the transmembrane domain. Here, we discuss possible gating mechanisms for electron transfer across the endosomal membrane.

    View details for DOI 10.1073/pnas.0801318105

    View details for Web of Science ID 000256378100015

    View details for PubMedID 18495927

  • The Steap proteins are metalloreductases BLOOD Ohgami, R. S., Campagna, D. R., McDonald, A., Fleming, M. D. 2006; 108 (4): 1388-1394

    Abstract

    Iron and copper are essential for all organisms, assuming critical roles as cofactors in many enzymes. In eukaryotes, the transmembrane transport of these elements is a highly regulated process facilitated by the single electron reduction of each metal. Previously, we identified a mammalian ferrireductase, Steap3, critical for erythroid iron homeostasis. Now, through homology, expression, and functional studies, we characterize all 4 members of this protein family and demonstrate that 3 of them, Steap2, Steap3, and Steap4, are not only ferrireductases but also cupric reductases that stimulate cellular uptake of both iron and copper in vitro. Finally, the pattern of tissue expression and subcellular localization of these proteins suggest they are physiologically relevant cupric reductases and ferrireductases in vivo.

    View details for DOI 10.1182/blood-2006-02-003681

    View details for Web of Science ID 000239698800047

    View details for PubMedID 16609065

  • nm1054: a spontaneous, recessive, hypochromic, microcytic anemia mutation in the mouse BLOOD Ohgami, R. S., Campagna, D. R., Antiochos, B., Wood, E. B., Sharp, J. J., Barker, J. E., Fleming, M. D. 2005; 106 (10): 3625-3631

    Abstract

    Hypochromic, microcytic anemias are typically the result of inadequate hemoglobin production because of globin defects or iron deficiency. Here, we describe the phenotypic characteristics and pathogenesis of a new recessive, hypochromic, microcytic anemia mouse mutant, nm1054. Although the mutation nm1054 is pleiotropic, also resulting in sparse hair, male infertility, failure to thrive, and hydrocephaly, the anemia is the focus of this study. Hematologic analysis reveals a moderately severe, congenital, hypochromic, microcytic anemia, with an elevated red cell zinc protoporphyrin, consistent with functional erythroid iron deficiency. However, serum and tissue iron analyses show that nm1054 animals are not systemically iron deficient. From hematopoietic stem cell transplantation and iron uptake studies in nm1054 reticulocytes, we provide evidence that the nm1054 anemia is due to an intrinsic hematopoietic defect resulting in inefficient transferrin-dependent iron uptake by erythroid precursors. Linkage studies demonstrate that nm1054 maps to a genetic locus not previously implicated in microcytic anemia or iron phenotypes.

    View details for DOI 10.1182/blood-2005-01-0379

    View details for Web of Science ID 000233187700052

    View details for PubMedID 15994289

  • Identification of a ferrireductase required for efficient transferrin-dependent iron uptake in erythroid cells NATURE GENETICS Ohgami, R. S., Campagna, D. R., Greer, E. L., Antiochos, B., McDonald, A., Chen, J., Sharp, J. J., Fujiwara, Y., Barker, J. E., Fleming, M. D. 2005; 37 (11): 1264-1269

    Abstract

    The reduction of iron is an essential step in the transferrin (Tf) cycle, which is the dominant pathway for iron uptake by red blood cell precursors. A deficiency in iron acquisition by red blood cells leads to hypochromic, microcytic anemia. Using a positional cloning strategy, we identified a gene, six-transmembrane epithelial antigen of the prostate 3 (Steap3), responsible for the iron deficiency anemia in the mouse mutant nm1054. Steap3 is expressed highly in hematopoietic tissues, colocalizes with the Tf cycle endosome and facilitates Tf-bound iron uptake. Steap3 shares homology with F(420)H(2):NADP(+) oxidoreductases found in archaea and bacteria, as well as with the yeast FRE family of metalloreductases. Overexpression of Steap3 stimulates the reduction of iron, and mice lacking Steap3 are deficient in erythroid ferrireductase activity. Taken together, these findings indicate that Steap3 is an endosomal ferrireductase required for efficient Tf-dependent iron uptake in erythroid cells.

    View details for DOI 10.1038/ng1658

    View details for Web of Science ID 000233045200028

    View details for PubMedID 16227996

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