EZH2 expression is associated with inferior overall survival in mantle cell lymphoma

Enhancer of zeste homolog 2 (EZH2) is a catalytic component of the polycomb repressive complex 2 (PRC2) which reduces gene expression via trimethylation of a lysine residue of histone 3 (H3K27me3). Expression of EZH2 has not been assessed systematically in mantle cell lymphoma (MCL). Expression of EZH2 was assessed by immunohistochemistry in 166 patients with MCL. We also assessed other PRC2 components and H3K27me3. Fifty-seven (38%) of MCL patients were positive for EZH2 using 40% cutoff. EZH2 expression was associated with aggressive histologic variants (65% vs. 29%, p < 0.001), high Ki-67 proliferation rate (median, 72% vs. 19%, p < 0.001), and p53 overexpression (43% vs. 2%, p < 0.001). EZH2 expression did not correlate with expression of other PRC2 components (EED and SUZ12), H3K27me3, MHC-I, and MHC-II. Patients with EZH2 expression (EZH2+) had a poorer overall survival (OS) compared with patients without EZH2 expression (EZH2-) (median OS: 3.9 years versus 9.4 years, respectively, p < 0.001). EZH2 expression also predicted a poorer prognosis in MCL patients with classic histology (median OS, 4.6 years for EZH2+ and 9.6 years for EZH2-negative, respectively, p < 0.001) as well as aggressive histology (median OS, 3.7 years for EZH2+ and 7.9 years for EZH2-negative, respectively, p = 0.046). However, EZH2 expression did not independently correlate with overall survival in a multivariate analysis. Gene expression analysis and pathway enrichment analysis demonstrated a significant enrichment in cell cycle and mitotic transition pathways in MCL with EZH2 expression. EZH2 expression detected by immunohistochemistry is present in 38% of MCL cases and it is associated with high proliferation rate, p53 overexpression, aggressive histologic variants, and poorer OS. Based on gene expression profiling data, EZH2 expression could potentiate cell cycle machinery in MCL. These data suggest that assessment of EZH2 expression could be useful to stratify MCL patients into low- and high-risk groups.

EBV-Positive Primary Large B-Cell Lymphoma: The Role of Immunohistochemistry and XPO1 in the Diagnosis of Mediastinal Lymphomas

Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is described as almost always negative for Epstein-Barr virus (EBV). In the context of a mediastinal lymphoma, the distinction between PMBL, classical Hodgkin lymphoma, diffuse large B-cell lymphoma, and mediastinal gray-zone lymphoma can be very difficult; hence, EBV positivity often argues against PMBL. We present a 19-year-old man with mediastinal mass morphologically consistent with PMBL. The tumor expressed classic immunophenotype, including positivity for CD20, CD19, MAL, OCT2, BOB1, BCL6, CD79a, and subset positivity for CD30. However, the tumor was EBV-positive by in situ hybridization. Next-generation sequencing detected somatic mutations in XPO1 (E571K), SMARCB1 (L356fs), and MYCC (T73A). Although the immunophenotype and XPO1 mutation are characteristic of PMBL, EBV expression is uncommon. Since EBV positivity can occur in rare PMBLs, it should not be the deciding factor in the diagnosis. This is the first EBV-positive PMBL in which mutational profiling has been reported. Aside from providing diagnostic support, the finding of the XPO1 E571K mutation may suggest a targeted therapeutic option.

Practical Applications in Immunohistochemistry: An Immunophenotypic Approach to the Spleen

CONTEXT.—

Even though immunohistochemistry is routinely used by pathologists, evaluation of immunohistochemistry in splenic lesions remains difficult for many. Classification of benign and splenic lesions often requires a combination of hematoxylin-eosin evaluation, immunophenotyping, and sometimes molecular testing. Immunohistochemical staining is essential in evaluating many splenic lesions, and requires an understanding of the normal compartments of the spleen.

OBJECTIVE.—

To address different immunohistochemical features used for identification and subclassification of different lesions of the spleen, as well as in the normal compartments of the spleen.

DATA SOURCES.—

The information outlined in this review article is based on our experiences with a variety of spleen cases, on the current World Health Organization classification of hematopoietic and lymphoid tumors, and on a review of English-language articles published during 2018.

CONCLUSIONS.—

Features for phenotyping normal spleen as well as a variety of splenic lesions, including littoral cell angioma and splenic marginal zone lymphoma, are discussed. Suggested immunopanels are provided to assist in the diagnosis of different lesions of the spleen.

Diagnostically relevant updates to the 2017 WHO classification of lymphoid neoplasms

The recent 2017 WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues contains a number of updates under the category of lymphoid neoplasms. These changes include introduction of new entities, amended classification or terminology, and addition of newly discovered diagnostic and molecular features. In this review, we perform a focused, concise summary of selected lymphoid neoplasms and discuss changes in their classification. Rather than a comprehensive overview, we place specific emphasis on important and diagnostically relevant aspects of each entity that are novel or different from the previous WHO iteration and bring the practicing pathologist quickly up to speed with the updated classification.

Genomic analysis of follicular dendritic cell sarcoma by molecular inversion probe array reveals tumor suppressor-driven biology

Follicular dendritic cell sarcoma is a rare malignant neoplasm of dendritic cell origin that is currently poorly characterized by genetic studies. To investigate whether recurrent genomic alterations may underlie the biology of follicular dendritic cell sarcoma and to identify potential contributory regions and genes, molecular inversion probe array analysis was performed on 14 independent formalin-fixed, paraffin-embedded samples. Abnormal genomic profiles were observed in 11 out of 14 (79%) cases. The majority showed extensive genomic complexity that was predominantly represented by hemizygous losses affecting multiple chromosomes. Alterations of chromosomal regions 1p (55%), 2p (55%), 3p (82%), 3q (45%), 6q (55%), 7q (73%), 8p (45%), 9p (64%), 11q (64%), 13q (91%), 14q (82%), 15q (64%), 17p (55%), 18q (64%), and 22q (55%) were recurrent across the 11 samples showing abnormal genomic profiles. Many recurrent genomic alterations in follicular dendritic cell sarcoma overlap deletions that are frequently observed across human cancers, suggesting selection, or an active role for these alterations in follicular dendritic cell sarcoma pathogenesis. In support of a tumor suppressor-driven biology, homozygous deletions involving tumor suppressor genes CDKN2A, RB1, BIRC3, and CYLD were also observed. Neither recurrent gains nor amplifications were observed. This genomic characterization provides new information regarding follicular dendritic cell sarcoma biology that may improve understanding about the underlying pathophysiology, provide better prognostication, and identify potential therapeutic markers for this rare disease.

Predominance of CD4+ T Cells in T-Cell/Histiocyte-Rich Large B-Cell Lymphoma and Identification of a Subset of Patients With Peripheral B-Cell Lymphopenia

OBJECTIVES

T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) is a morphologic variant of large B-cell lymphoma whose flow cytometry findings are not well characterized.

METHODS

Nineteen cases with flow cytometric immunophenotyping were identified from the case records of four institutions between 2001 and 2016.

RESULTS

In most cases, neoplastic B cells were not detected by flow cytometry. Overall, cases showed a predominance of CD4+ T cells, which in some cases was marked. Significant coexpression of CD57 was seen on CD4+ T cells where this marker was analyzed, which correlated with PD-1 expression. Two cases also showed a profound systemic B-cell lymphopenia, which was associated in one case with hypogammaglobulinemia.

CONCLUSIONS

Overall, our work challenges previous findings that cases of THRLBCL are rich in CD8+ T cells and highlights parallels between THRLBCL and nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL). Also, an association of THRLBCL with systemic B-cell lymphopenia has not been previously reported but may represent an underrecognized manifestation.

Crystal-storing histiocytosis: a clinicopathological study of 13 cases

AIMS

Crystal-storing histiocytosis (CSH) is a rare lesion composed of histiocytes with abnormal intralysosomal accumulation of immunoglobulin (Ig) as crystals, reported in patients with plasmacytic/lymphoplasmacytic neoplasms. The aims of this study were to report the clinicopathological features of 13 patients with CSH, and to describe the proteomic composition of the crystals in three cases analysed by mass spectrometry (MS).

METHODS AND RESULTS

There were seven men and six women, with a median age of 60 years (range, 33-79 years). CSH was generalized in one patient (8%) and localized in 12 (92%) patients, involving various sites. CSH was associated with a low-grade B-cell lymphoma with plasmacytoid differentiation or a plasma cell neoplasm in all cases. In 10 (77%) cases, CSH represented >50% of the neoplastic infiltrate. According to immunohistochemical studies, histiocytes were positive for monotypic kappa in 5 (50%) cases, and for monotypic lambda in 4 (40%) cases; in 1 (10%) case, the results were equivocal. MS analysis of the histiocyte contents in all three tested cases showed a predominance of variable-region fragments of Ig light and/or heavy chains.

CONCLUSIONS

CSH is frequently associated with an underlying lymphoplasmacytic neoplasm. MS findings suggest that Ig alterations and/or possibly defects in the ability of histiocytes to process Ig play a role in pathogenesis.

Recommendations for gross examination and sampling of surgical specimens of the spleen

This review examines handling and processing of spleen biopsies and splenectomy specimens with the aim of providing the pathologist with guidance in optimizing examination and diagnosis of splenic disorders. It also offers recommendations as to relevant reporting factors in gross examination, which may guide diagnostic workup. The role of splenic needle biopsies is discussed. The International Spleen Consortium is a group dedicated to promoting education and research on the anatomy, physiology, and pathology of the spleen. In keeping with these goals, we have undertaken to provide guidelines for gross examination, sectioning, and sampling of spleen tissue to optimize diagnosis (Burke). The pathology of the spleen may be complicated in routine practice due to a number of factors. Among these are lack of familiarity with lesions, complex histopathology, mimicry within several types of lesions, and overall rarity. To optimize diagnosis, appropriate handling and processing of splenic tissue are crucial. The importance of complete and accurate clinical history cannot be overstated. In many cases, significant clinical history such as previous lymphoproliferative disorders, hematologic disorders, trauma, etc, can provide important information to guide the evaluation of spleen specimens. Clinical information helps plan for appropriate processing of the spleen specimen. The pathologist should encourage surgical colleagues, who typically provide the specimens, to include as much clinical information as possible.

Evidence of BRAF V600E in indeterminate cell tumor and interdigitating dendritic cell sarcoma

BRAF V600E mutations have been reported in several histiocytic and dendritic cell neoplasms. In this case series, we report BRAF V600E-positive histiocytic and dendritic cell neoplasms in association with lymphomas and lymphoid proliferations. This is a review of cases with immunohistochemistry for BRAF V600E, with additional immunohistochemistry to categorize tumors. We report the first case of BRAF V600E-positive indeterminate cell tumor in association with angioimmunoblastic T-cell lymphoma. We also report a case of BRAF V600E-positive interdigitating dendritic cell sarcoma in a patient with positive B-cell polymerase chain reaction. It is unclear if these neoplasms developed as transdifferentiation of lymphoid neoplasms or if they developed independently. These cases illustrate the expanding spectrum of BRAF V600E-positive histiocytic and dendritic cell tumors and suggest that attention should be paid to lymphomas for possible coincident presentation of these disorders.

Distinctive immunohistochemical staining in littoral cell angioma using ERG and WT-1

Littoral cell angioma (LCA) is a rare vascular tumor of the spleen. It has an immunohistochemical staining pattern that is somewhat distinctive but can still be occasionally confused with other vascular and stromal proliferations in the spleen. In this study, LCA was evaluated using Ets-related gene (ERG) and Wilms tumor-1 (WT-1), relatively recently described vascular markers. In addition, other vascular lesions including normal spleen, hemangiomas, hamartoma, peliosis, and sclerosing angiomatoid nodular transformation were evaluated using these stains. In LCA, ERG stains the endothelial cells of the tumor as expected. ERG also was uniformly positive in vascular elements of other lesions except peliosis. However, in contrast to most other vascular elements, LCA was negative for WT-1 staining. This staining pattern may prove useful in diagnosing LCA and may provide insight into the derivation of the distinctive tumor.

Practical Applications in Immunohistochemistry: Evaluation of Diffuse Large B-Cell Lymphoma and Related Large B-Cell Lymphomas

Context

Diffuse large B-cell lymphoma is the most commonly diagnosed subtype of lymphoma worldwide. The current World Health Organization (WHO) classification includes several subtypes, based on a combination of clinical, immunohistochemical, and genetic differences. Immunohistochemical staining is essential in evaluating diffuse large B-cell lymphoma and many related large B-cell lymphomas and aggressive B-cell lymphomas.

Objective

To address different immunohistochemical features used for identification, subclassification, prognosis and in some cases, therapy, of diffuse large B-cell lymphoma and related lymphomas.

Data Sources

The information outlined in this review article is based on our experiences with routine cases, on the current WHO classification of hematopoietic and lymphoid tumors, and on a review of English-language articles published throughout 2014.

Conclusions

Features and diagnostic criteria of diffuse large B-cell lymphoma, aggressive variants of B-cell lymphomas, including Burkitt lymphoma and “double-hit” lymphomas, are discussed. Identification of cell of origin (germinal center type versus activated B-cell type) is discussed at length. Finally, practical approaches for diagnosis are discussed.

Breast implant-associated anaplastic large-cell lymphoma: long-term follow-up of 60 patients

PURPOSE

Breast implant-associated anaplastic large-cell lymphoma (ALCL) is a recently described clinicopathologic entity that usually presents as an effusion-associated fibrous capsule surrounding an implant. Less frequently, it presents as a mass. The natural history of this disease and long-term outcomes are unknown.

PATIENTS AND METHODS

We reviewed the literature for all published cases of breast implant-associated ALCL from 1997 to December 2012 and contacted corresponding authors to update clinical follow-up.

RESULTS

The median overall survival (OS) for 60 patients was 12 years (median follow-up, 2 years; range, 0-14 years). Capsulectomy and implant removal was performed on 56 of 60 patients (93%). Therapeutic data were available for 55 patients: 39 patients (78%) received systemic chemotherapy, and of the 16 patients (28%) who did not receive chemotherapy, 12 patients opted for watchful waiting and four patients received radiation therapy alone. Thirty-nine (93%) of 42 patients with disease confined by the fibrous capsule achieved complete remission, compared with complete remission in 13 (72%) of 18 patients with a tumor mass. Patients with a breast mass had worse OS and progression-free survival (PFS; P = .052 and P = .03, respectively). The OS or PFS were similar between patients who received and did not receive chemotherapy (P = .44 and P = .28, respectively).

CONCLUSION

Most patients with breast implant-associated ALCL who had disease confined within the fibrous capsule achieved complete remission. Proper management for these patients may be limited to capsulectomy and implant removal. Patients who present with a mass have a more aggressive clinical course that may be fatal, justifying cytotoxic chemotherapy in addition to removal of implants.

Abnormal expression of CD20 on IgG4 plasma cells associated with IgG4-related lymphadenopathy

CONTEXT

Immunoglobulin G4 (IgG4)-related disease is a recently described entity that presents as mass-forming lesions in soft tissue, exocrine glands, and in lymph nodes as IgG4-related lymphadenopathy. The underlying pathologic mechanism of IgG4-related disease is unclear; however, rituximab (an anti-CD20 monoclonal antibody) has been shown to have clinical efficacy.

OBJECTIVE

To look for the presence or absence of CD20 on the IgG4-expressing plasma cells in IgG4-related lymphadenopathy.

DESIGN

Twelve flow cytometry cases were identified through a retrospective review from the authors' institutions files. Cases were selected by the presence of a lymph node biopsy specimen with increased IgG4 plasma cells by immunohistochemistry and a histologic diagnosis compatible with IgG4-related lymphadenopathy.

RESULTS

We report dim CD20 expression on plasma cells in all cases for which a plasma cell population was clearly identified by flow cytometry. These cases were from patients with lymph node biopsy specimens that met published criteria for IgG4-related lymphadenopathy.

CONCLUSIONS

This finding may be one potential explanation for the clinical efficacy of rituximab in IgG4-related disease.

The genetics of interdigitating dendritic cell sarcoma share some changes with Langerhans cell histiocytosis in select cases

Histiocytic disorders have been noted to have evidence of transdifferentiation; examples of cases with combinations of different lineages have been shown. In our index case, we identified interdigitating dendritic cell (IDC) differentiation in a case of Langerhans cell histiocytosis (LCH). Little is currently known about the genetics of IDC sarcoma (IDCS) because they are exceedingly rare. Using array comparative genomic hybridization (aCGH), we evaluated 4 cases of IDCS and compared them with our index case, as well as genetic abnormalities previously found in LCH. Four cases of paraffin-embedded samples of IDCS and 1 case of LCH with IDC differentiation were evaluated using aCGH. Array CGH results showed no abnormalities in a case of LCH with interdigitating cell differentiation. In 3 of 4 cases of IDCS, genetic abnormalities were identified; 1 case had no identifiable abnormalities. Interdigitating dendritic cell sarcoma case 1 had gains of 3q and 13q; IDCS case 2 had trisomy 12; IDCS case 3 had deletions of 7p, 12p, 16p, 18q, 19q, and 22q; and IDCS case 4 had no detectable abnormalities. Our index case, LCH with IDC differentiation, showed no abnormalities by aCGH. A number of LCH cases do not have detectable genetic abnormalities. In contrast, 3 of 4 cases of IDCS evaluated had identifiable abnormalities by aCGH. Furthermore, 2 of these shared abnormalities, albeit of large genetic regions, with published abnormalities seen in LCH. No recurrent abnormalities were identified in the IDCS cases. However, the possibility of a relationship between IDCS and LCH cannot be entirely excluded by these results.

Co-occurrence of Langerhans cell histiocytosis and Rosai-Dorfman disease: possible relationship of two histiocytic disorders in rare cases

Rosai-Dorfman disease and Langerhans cell histiocytosis are both disorders of accessory immune cells. Two cases have been previously reported of concurrent Langerhans cell histiocytosis and Rosai-Dorfman disease. In this report, we characterize the findings and selected molecular studies in nine additional cases. Histology was reviewed. Immunohistochemical stains were performed on all cases in which slides or blocks were available. A combination of CD1a, S-100, CD3, CD20, langerin, CD68, CD163, CD21, CD35 and CD123 immunohistochemical stains were performed. High-resolution array comparative genomic hybridization was performed on six samples from five cases. In these cases, seven were female and two male, with an average age of 25 years (15 months-59 years). A majority of the cases were identified in lymph node. Areas of Langerhans cell histiocytosis had a typical appearance with the existence of bland 'coffee-bean' nuclei, clear cytoplasm and associated eosinophils. The immunophenotype was typical, including expression of CD1a, S100, CD68 and langerin. In areas of Rosai-Dorfman disease, there was emperipolesis seen in all cases. Cells were intermediate-large in size with large round nuclei and ample clear or pale cytoplasm. The lesional cells were positive for S100, CD68, CD163, without expression of langerin or CD1a. Array comparative genomic hybridization showed gains and/or losses in four of the six samples. One case showed no gains or losses and one additional case showed gains and losses in the Langerhans cell histiocytosis, while no abnormalities were discovered in the Rosai-Dorfman disease component. These findings are comparable to those seen in previous studies of Langerhans cell histiocytosis. We report the clinical and pathologic findings of the combination of Langerhans cell histiocytosis and Rosai-Dorfman disease. Furthermore, we suggest on the basis of evidence from our cases that, when simultaneous, the two entities may be pathophysiologically related.

Myeloid leukemia cutis: a histologic and immunohistochemical review

BACKGROUND

The histologic diagnosis of myeloid leukemia cutis (LC) can be difficult, requiring confirmatory immunohistochemical stains.

OBJECTIVE

We reviewed 21 biopsy-proven cases of LC with emphasis on the use of immunohistochemistry in the diagnosis.

MATERIALS AND METHODS

Clinical and histologic features were reviewed on 21 cases of biopsy proven LC. Immunohistochemical stains for CD4, CD34, CD56, CD68, CD117, CD123, TdT, lysozyme and myeloperoxidase were performed on 12 with available tissue blocks.

RESULTS

Ages ranged from 24 to 88 years (mean = 57), with 12 men: 9 women. Primary hematologic diagnoses included acute myeloid leukemia (n = 14), myelodysplastic syndrome (n = 3), essential thrombocythemia (n = 1) and myeloid leukemia, NOS (n = 3). Monocytic myeloid LC was most common (35%). There was 100% positivity with CD68 and lysozyme. Myeloperoxidase, CD117 and CD34 immunostains were less sensitive in myeloid LC (58%, 33% and 17%, respectively). CD4 was positive in 67%. CD56 was positive in 33%.

CONCLUSION

Myeloid leukemia with monocytic differentiation more commonly involves the skin than other types of myeloid leukemia. CD68 and lysozyme immunostains, although not lineage specific for monocytes/macrophages, are the most sensitive immunostains in the detection of myeloid LC. Myeloperoxidase immunostains are useful, but immunostains for CD117 and CD34 are insufficiently sensitive. CD4 expression is common, but CD56 expression is not.

Primary mediastinal B-cell lymphoma: detection of BCL2 gene rearrangements by PCR analysis and FISH

Primary mediastinal large B-cell lymphoma (PMBCL) has a characteristic clinical presentation, morphology, and immunophenotype, representing a clinically favorable subgroup of diffuse large B-cell lymphoma (DLBCL). By gene expression profiling (GEP), PMBCL shares features with classical Hodgkin lymphoma (cHL). Of further interest, BCL6 gene mutations and BCL6 and/or MUM1 expression in a number of PMBCLs have supported an activated B-cell (ABC) origin. Several studies, including GEP, have failed to detect BCL2 gene rearrangements (GRs) in PMBCL. An index case of t(14; 18)+ PMBCL prompted our study of the incidence of BCL2 GRs in PMBCL by polymerase chain reaction (PCR)/fluorescence in situ hybridization (FISH) analyses and its possible clinical impact. Twenty-five retrospectively identified, well-defined PMBCLs (five with cytogenetics) from three institutions were analyzed for a BCL2 GR by PCR/FISH analyses. The formalin-fixed, paraffin-embedded tissue blocks of 24 available cases were also analyzed by BCL2 immunohistochemistry (IHC). Of the five with cytogenetics, two had a t(14; 18) (q32; q21). Of the 25 analyzed by PCR, 2 had no amplifiable DNA (aDNA), including 1 t(14; 18)+ case. Of those with aDNA, two showed a BCL2 GR; by FISH analysis, three demonstrated a BCL2 GR. BCL2 protein expression by IHC analysis was variably detected in 21 out of 24 (strongly, uniformly expressed: 6, including all with a t(14; 18) or a BCL2 gene rearrangement; moderately weakly expressed in a subset of the malignant cells: 15). Available clinical follow-up of this BCL2+ subset showed a similar course to the other PMBCL cases. Our results imply that a subset of PMBCL [(4 out of 24 analyzed) in our series] may be of GC origin. A larger study is necessary to determine any clinical significance.

Loss of heterozygosity identifies genetic changes in chronic myeloid disorders, including myeloproliferative disorders, myelodysplastic syndromes and chronic myelomonocytic leukemia

This study evaluates changes in genetic loci of chronic myeloid disorders using loss of heterozygosity (LOH) techniques. We present the combined results of three experiments. First, examination of a panel of genetic loci in groups of myeloproliferative disorders was evaluated. The second experiment involved microdissection of megakaryocytes from myeloproliferative disorders and comparison of their genetic changes to surrounding neoplastic marrow elements. Finally, we compared results of LOH studies of myeloproliferative disorders to those of myelodysplastic syndromes and chronic myelomonocytic leukemia. A total of 41 bone marrow biopsies were evaluated. Twenty-seven were myeloproliferative disorders (11 chronic idiopathic myelofibrosis, 11 essential thrombocythemia, 5 polycythemia vera). The remaining cases consisted of myelodysplastic syndromes (total=5; RAEB-1=2; RAEB-2=2; MDS, not otherwise specified=1) and chronic myelomonocytic leukemia (n=8). The abnormalities in myeloproliferative disorders were distributed as follows: D7S2554-4/14 (5/14); D8S263-4/15 (5/15); D9S157-5/15 (5/15); D9S161-7/17 (6/17); D13S319-5/14 (4/14); TP53-5/16 (5/16); D20S108-4/15 (4/15). In 75% cases diagnosed as essential thrombocythemia (6/8), both cases of polycythemia vera (2/2), and 29% cases of chronic idiopathic myelofibrosis (2/7), there were genetic differences between the megakaryocytes and the surrounding marrow. These results suggest that in some cases, megakaryocytes have different clonal abnormalities than surrounding hematopoietic tissue. The genetic profiles of myeloproliferative disorders had several differences from those of myelodysplastic syndromes. Although different from both, chronic myelomonocytic leukemia appeared more similar to myeloproliferative disorders using these techniques.

Loss of Heterozygosity Analysis Identifies Genetic Abnormalities in Mycosis Fungoides and Specific Loci Associated With Disease Progression

Mycosis fungoides (MF) exhibits a variety of underlying molecular defects. Loss of heterozygosity (LOH) is a technique used to detect chromosomal imbalances in neoplastic disorders using archival tissue. We analyzed skin biopsies of MF in different stages for the presence of LOH at specific loci to evaluate underlying genetic aberrations involved in MF and its progression. Twenty-five skin biopsies (15 plaque stage and 10 tumor stage) from 19 patients were evaluated. LOH was examined at 1p22 (D1S2766), 9p21 [IFNA, p15 (D9S1748), p16 (D9S171)], 10q23 [PTEN (D10S185, D10S541, D10S2491)], and 17p13 [p53 (TP53)]. Abnormal lymphocytes were microdissected from formalin-fixed, paraffin-embedded tissue sections. Sixteen of the 25 (64%) specimens evaluated had at least one abnormal LOH locus and LOH was identified in 7 of 15 (47%) plaque and in 9 of 10 (90%) tumor stage lesions, respectively. All 3 patients with sequential biopsies (plaque followed by tumor lesions) had additional LOH abnormalities in tumor specimens compared with plaque stage lesions. LOH most frequently involved chromosome 10, including 7 of 10 (70%) tumor stage lesions. Loss of multiple alleles was only identified in tumor stage cases, with 3 tumors undergoing allelic losses at 3 separate loci. Our results suggest that LOH studies are a robust method for evaluating genetic abnormalities in MF. Tumor stage lesions manifest increasing allelic losses compared with plaque stage. Further, in this series, several loci associated with the tumor suppressor gene PTEN on chromosome 10 appear to be associated with progression from plaque to tumor stage.

The role of Janus Kinase 2 V617F mutation in extramedullary hematopoiesis of the spleen in neoplastic myeloid disorders

Extramedullary hematopoiesis (EMH) in the spleen is a characteristic feature of the chronic myeloproliferative disorders (CMPDs) and various other neoplastic or reactive myeloid conditions. However, the origin of these hematopoietic precursor cells and the molecular mechanisms underlying their development in the spleen is uncertain. The V617F mutation in the Janus Kinase 2 gene (JAK2(V617F)) was recently shown to be frequently and preferentially present in the peripheral blood and bone marrow cells of CMPD patients, and the resulting dysregulation of its downstream targets is important to CMPD pathogenesis. To determine the occurrence and potential role of JAK2(V617F) in splenic EMH cells, we studied splenectomy specimens from 47 patients with significant EMH. JAK2(V617F) was detected by real-time PCR melting curve analysis in 22 specimens, including 11/17 chronic idiopathic myelofibrosis, 7/7 polycythemia vera, 1/1 essential thrombocythemia, 1/3 CMPD unclassifiable, 1/5 chronic myelomonocytic leukemia, 0/5 chronic myelogenous leukemia, 1/3 myelodysplastic syndrome and 0/6 acute myeloblastic leukemia cases, whereas only the JAK2 wild-type allele was detected in the other 25. Nineteen of 20 cases with adequate bone marrow samples available for molecular examination demonstrated concordant JAK2 genotypes. Laser-capture microdissection was then used to enrich the EMH and non-EMH splenic cell fractions, confirming that the mutant alleles specifically originated from the EMH cells. Furthermore, megakaryocytes in the JAK2(V617F)-positive splenectomy specimens expressed higher levels of Bcl-xL, an antiapoptotic protein and downstream target of the JAK2/STAT5 pathway. Thus, JAK2(V617F) is frequently present in splenic EMH cells associated with CMPD, but it is rarely identified in splenic EMH cells associated with other myeloid disorders. Our results indicate that the precursor cells leading to extramedullary hematopoietic expansion in CMPD most likely originate from the transformed bone marrow clone. Also, dysregulation of downstream pathways such as Bcl-xL may be important to CMPD disease pathogenesis in the spleen.

T-cell large granular leukemia and related proliferations

Session 9 of the 2005 Society for Hematopathology/European Association for Haematopathology Workshop focused on large granular lymphocyte (LGL) leukemias and related disorders. T-cell LGL (T-LGL) leukemias, discussed herein, account for 2% to 3% of cases of small lymphocytic leukemia. T-LGL diseases cover a heterogeneous spectrum of disorders that include reactive conditions, typically associated with autoimmune disease, to outright leukemia. These disorders are found in older people, with an average age at initial examination of approximately 60 years and a median survival of more than 10 years in T-LGL leukemia. Systemic symptoms and neutropenia are common at initial examination. Lymphocytosis, composed of small mature lymphocytes with increased cytoplasm, is common. The spleen and bone marrow are involved in T-LGL leukemia, although morphologic findings may be subtle. The immunophenotype is typically that of CD3+/CD8+ cytotoxic T cells. Some cases may be due to chronic immune stimulation, with subsequent clonal escape and proliferation of a neoplastic population of lymphocytes.

Analysis of Immunohistochemical Markers in Bone Marrow Sections to Evaluate for Myelodysplastic Syndromes and Acute Myeloid Leukemias

BACKGROUND

Accurate bone marrow (BM) blast counts (BCs) are essential for diagnosis (dx) of myelodysplasia (MDS), MDS/myeloproliferative (MDS/MPD) disease, or acute myeloid leukemia (AML), and may be difficult in hemodiluted bone marrow aspirates (BMAs). Erythroid precursors (EPs) may be indistinguishable from myeloblasts in BM sections (aspirate clots/cores). We compare the usefulness of immunohistochemistry (IHC) [ie, CD34, CD117, myeloperoxidase (MPO), Hemoglobin A1 (HbA1), and terminal deoxynucleotidyl transferase (TdT)] of BM sections (IHC-BM) with BMA, bone marrow touch preparation (BMTP), and flow cytometry (FC) BCs.

DESIGN

The initial BC (48), percentage (%) of Eps (38) (both based on initial 100 to 600-cell counts), and FC expressions of CD34, CD117, Glycophorin A(GLY A), and TdT (44) were tabulated from 50 BMs (MDS, MDS/MPD, or AML). BMAs (48) and BMTPs (25) subsequently received 500-cell counts. IHC-BM was performed (45:formalin, 5:B5-fixed) [CD34 (46), CD117 (45), HbA1 (45), TdT (42), and MPO (45)].

RESULTS

Retrospective BMA BCs revealed a 31% (15/48) discrepant rate between the original/retrospective BMA BCs; 80% revealed an underestimated initial BC. There was a 28% discordance rate between the retrospective BMA and BMTP reviews; 77% showed a higher BMTP BC. IHC showed significantly higher BCs in 19% (9/47), resulting in a different dx (5). However, CD34 and CD117 IHCS revealed lower BCs in 38% and 48%, respectively. The CD34 IHC results were primarily due to CD34-negative blasts by FC. The CD117 IHC results were largely unexplained. EPs were CD34 and CD117-negative.

CONCLUSIONS

(1) Evaluation for MDS/AML requires 500-cell counts of BMAs and/or BMTPs. (2) CD34 and/or CD117 blasts by FC indicate IHC-BM may increase BC accuracy. (3) CD34 is more reliable than CD117 by IHC; however, in combination, they are most reliable and should be performed on BM clots/cores due to variable reactivity.

Benign extramedullary myeloid proliferations

Extramedullary proliferations of bone marrow elements are infrequently encountered in routine pathology practice. On occasion, they can present diagnostic difficulties when seen in unusual or unanticipated sites. This review serves to cover aspects of underlying embryogenesis of myeloid elements, as well as sites and circumstance of benign proliferations of myeloid elements along with their occasional confusion with neoplastic myeloid proliferations. Benign proliferations associated with hematologic disorders and hematopoietic growth factors are discussed. Immunohistochemical evaluation of myeloid proliferations is considered as well.

Epstein-Barr-associated leiomyomatosis and T-cell chimerism after haploidentical bone marrow transplantation for severe combined immunodeficiency disease

BACKGROUND

The clinical course of Epstein-Barr virus (EBV)-associated smooth muscle tumors is variable and there are no reports in patients with mixed T-cell chimerism after bone marrow transplantation (BMT).

OBSERVATIONS

A child with X-linked severe combined immunodeficiency disease developed multiple renal and pulmonary leiomyomata 8 years after haploidentical BMT. Epstein-Barr viral DNA was detectable in the blood and in situ hybridization for EBV-encoded RNAs was positive in the tumor. The tumors have been radiographically stable, chimerism remains mixed, and plasma EBV DNA has been repeatedly negative for over 2 years after donor lymphocyte infusion.

CONCLUSIONS

EBV-associated smooth muscle tumors may occur in patients who are partially reconstituted after BMT for severe combined immunodeficiency and may not require surgery or chemotherapy.

CD4+ CD56+ Hematodermic Neoplasm

We report a case of a 75-year-old man with a cutaneous CD4+CD56+ hematodermic neoplasm. CD4+CD56+ hematodermic neoplasms are rare and commonly present as cutaneous lesions. This is an important diagnosis in the differential diagnosis of cutaneous hematologic malignancies because of the extremely poor prognosis.

Chronic myelomonocytic leukemia: The role of bone marrow biopsy immunohistology

The World Health Organization criteria for diagnosing chronic myelomonocytic leukemia (CMML) are largely based on findings observed in the peripheral blood and bone marrow aspirate. A specific diagnostic role for the bone marrow biopsy has not been adequately explored. We examined whether bone marrow biopsy supplemented by immunohistochemistry may be helpful in distinguishing CMML from cases of chronic myelogenous leukemia and atypical chronic myeloid leukemia (aCML). We immunostained 25 cases of CMML with paraffin reactive antibodies which included CD68 (KP1), CD68R (PG-M1), and CD163, and compared the results with those observed in six cases of chronic myelogenous leukemia and in three cases of atypical CML. In addition, we examined whether CD34 immunohistochemistry could be useful in separating cases of CMML with less than 10% blasts (type-1) from cases of CMML with blasts accounting for 10-19% (type-2), and cases of CMML in acute transformation to acute myeloid leukemia (blasts > or = 20%). The presence of nodules of plasmacytoid monocytes was investigated by CD123 staining. CD42b was used to highlight abnormal megakaryocytes. Our results demonstrate significant differences between the groups. CD34 analysis allowed separating CMML type-1 from type-2 and the former from CMML in acute transformation. CD123-positive plasmacytoid monocyte nodules were found only in CMML and not in the other two disease groups. Overlap between CMML and the other two groups were observed with CD68 immunostaining. CD68R was more restricted to bone marrow macrophages and monocytes than CD68, but the differences between CMML and chronic myelogenous leukemia or atypical CML were still not significant. Although CD42b immunostaining facilitated the detection of dwarf megakaryocytes often present in CMML, the distinction between those and the small forms seen in chronic myelogenous leukemia was still problematic.

Adrenal myelolipomas show nonrandom X-chromosome inactivation in hematopoietic elements and fat: support for a clonal origin of myelolipomas

Myelolipomas are defined as mature fat associated with hematopoietic elements, often found in the adrenal gland. The question of whether the hematopoietic cells are truly "normal" has not been evaluated extensively. In this study, we evaluated histologic, immunohistochemical features and comparisons of X-chromosome inactivation patterns in 19 myelolipomas. Formalin-fixed, paraffin-embedded tissue from 19 myelolipomas was stained with hematoxylin and eosin and immunostained with monoclonal antibodies against CD138, CD34, CD117, CD42a, hemoglobin, myeloperoxidase, collagen IV, and nerve growth factor receptor. Histologic evaluation included estimates of overall cellularity of hematopoietic tissue, estimates of cellularity in the areas of highest concentration of hematopoietic tissue, myeloid to erythroid ratio, and numbers of megakaryocytes. X-chromosome inactivation analysis was performed on myelolipomas from 11 female patients by polymerase chain reaction. Myelolipomas showed wide variation in cellularity within the lesion (5% to 90%) with no correlation with the patient's age. All the myelolipomas demonstrated normal trilineage hematopoiesis and cellular morphology, with few early myeloid precursors, as evidenced by negativity for CD117 and only rare positivity for CD34 antibodies. Most of the myelolipomas (14/18) had markedly increased megakaryocytes compared with normal marrows. The majority of myelolipomas also had a stromal composition and vascular patterns that were different from those of normal bone marrow. X-chromosome inactivation studies demonstrated nonrandom X-chromosome inactivation in 8/11 myelolipomas from female patients. Myelolipomas are morphologically different from the normal bone marrow. The majority of myelolipomas also have nonrandom X-chromosome inactivation, suggesting a clonal origin for these tumors.

Terminal deoxynucleotidyl transferase-positive cells in spleen, appendix and branchial cleft cysts in pediatric patients

We evaluated spleens (n = 26), appendices (n = 10) and branchial cleft cysts (n = 6) for TdT-positive cells in pediatric patients. In spleen, appendix and branchial cleft cysts the range of TdT-positivity was 0-13, 0-96 and 0-6 TdT+ cells/hpf, respectively. In spleens, scattered TdT+ cells were seen most frequently in periarteriolar lymphoid sheath regions.

Ki67 staining pattern as a diagnostic tool in the evaluation of lymphoproliferative disorders

AIMS

To evaluate a group of lymphoid proliferations using only Ki67-stained slides to determine the value of the pattern of proliferating cells in diagnosis. Ki67 immunohistochemistry allows evaluation of the distribution of proliferating cells in addition to simply determining the proliferation rate of cells.

METHODS AND RESULTS

Three observers, using a Ki67-stained slide only, studied 149 cases from five diagnostic groupings: follicular hyperplasia, mixed pattern hyperplasia, localized Castleman's disease, follicular lymphoma and marginal zone lymphoma. The sensitivity for benign lesions varied from 94% to 97% among the three observers. Follicular lymphomas were recognized as neoplastic with a sensitivity of 96% and 100% by two of the observers. Marginal zone lymphoma was recognized as neoplastic in 67-73% of cases.

CONCLUSIONS

The Ki67 stain alone is a powerful tool for distinguishing benign from malignant proliferations within the selected groups. Nuances and pitfalls in the interpretation of Ki67 staining pattern are discussed.

Evaluation of stroma in human immunodeficiency virus/acquired immunodeficiency syndrome-affected bone marrows and correlation with CD4 counts

CONTEXT

Little is known about cellular and extracellular composition of fibrosis in bone marrows in the context of human immunodeficiency virus/acquired immunodeficiency syndrome.

OBJECTIVE

To evaluate the stromal composition of bone marrows affected by human immunodeficiency virus/ acquired immunodeficiency syndrome and to correlate this with laboratory parameters including CD4 lymphocyte counts.

DESIGN

We evaluated extracellular matrix and stromal cell composition in bone marrows and correlated these results with hematologic parameters. Extracellular matrix, stromal cells, and smooth muscle differentiation were evaluated by immunohistochemistry for collagen type IV expression and reticulin staining, an antibody directed against low-affinity nerve growth factor receptor (a marker of adventitial reticular cells), and actin staining, respectively. Concurrent laboratory information was collected, including white blood cell count, hemoglobin, platelet count, CD4 count, CD8 count, CD4/CD8 ratio, and absolute lymphocyte count.

PATIENTS

Bone marrows of 35 patients with human immunodeficiency virus/acquired immunodeficiency syndrome were evaluated.

MAIN OUTCOME MEASURES

Correlation of reticulin, low-affinity nerve growth factor receptor, actin, and collagen IV staining with hematologic parameters.

RESULTS

More than half of the bone marrows showed moderate to severe reticulin fibrosis. The degree of reticulin fibrosis was correlated with the degree of low-affinity nerve growth factor receptor expression (P = .048). Actin expression was identified in only 3 of 35 cases and collagen IV in only 5 of 35 cases. No statistical relationship between degree of fibrosis and CD4 count was identified. Lower levels of low-affinity nerve growth factor receptor expression were associated with CD4 counts of >100 (P = .04). Marrow fibrosis was present in almost all cases studied (97%), and the staining of adventitial reticular cells correlated with the degree of reticulin fibrosis.

CONCLUSIONS

There does not appear to be a correlation between CD4 count and degree of fibrosis, suggesting that the mechanism of fibrosis is independent of disease status.

Analysis of loss of heterozygosity and X chromosome inactivation in spleens with myeloproliferative disorders and acute myeloid leukemia

Neoplastic myeloid proliferations are seen in the spleens of some patients with acute and chronic myeloproliferative disorders. Both acute myeloid leukemia (AML) and chronic myeloproliferative disorders have a variety of underlying cytogenetic defects that can be evaluated by loss of heterozygosity (LOH) studies. LOH studies have advantages over conventional cytogenetics by allowing the use of archival tissues. We evaluated the spleens in AML and chronic myeloproliferative disorders with neoplastic myeloid proliferations for the presence of LOH at several chromosome loci, and X-chromosome inactivation. A total of 17 spleens were evaluated (chronic myelogenous leukemia = 6; chronic idiopathic myelofibrosis = 6; essential thrombocythemia = 1; AML arising from previous chronic myeloproliferative disorders = 4). We examined LOH loci 7q (D7S2554), 8q (D8S263), 9p (D9S157, D9S161), 13q (D13S319), common sites of genetic abnormality in chronic myeloproliferative disorders, and TP53. In six cases, spleen LOH findings were compared to those of concurrent or preceding bone marrow biopsies. Five spleens of female patients were evaluated for the presence of clonality using X-chromosome inactivation. Of the 16 cases analyzed, 14 (88%) had at least one abnormal LOH locus, with 6/16 with two abnormal loci. The abnormalities were distributed as follows: D9S161-7/15 (47%), TP53-6/16 (38%), D7S2554-5/16 (31%), D9S157-5/15 (33%), D8S263-3/14 (21%), and D13S319-2/14 (14%). Of the six bone marrows, 4/6 showed concordance in bone marrow and spleen specimens, with additional LOH abnormalities being identified in the spleen specimens of all four cases. X-chromosome inactivation studies were showed nonrandom (clonal) patterns in two cases. Our results show that allelic losses were common in the neoplastic extramedullary hematopoiesis found in spleens of chronic myeloproliferative disorders and AML. Comparison of spleen and bone marrow specimens by LOH demonstrated additional abnormalities in the spleen compared to the marrow.

Morphologic and immunohistochemical evaluation of splenic hematopoietic proliferations in neoplastic and benign disorders

Spleen is a common site of extramedullary hematopoiesis. Extramedullary hematopoiesis seen in non-neoplastic conditions can occasionally be extensive and raise concerns for a myeloid neoplasm. We compared the morphologic and immunohistochemical features of splenic hematopoietic proliferations seen in neoplastic myeloid disorders (eg chronic myeloproliferative disorders, myelodysplastic/myeloproliferative disorders and acute myeloid leukemias) to extramedullary hematopoiesis seen in a variety of reactive conditions. In all, 80 spleen specimens were reviewed. The presence of each marrow-derived lineage, dysplasia and immunohistochemical results were evaluated (CD34, CD117, myeloperoxidase, CD68, p53, TdT, CD42b and hemoglobin). Neoplastic hematopoietic proliferations in chronic myeloproliferative disorders are characterized by trilineage hematopoiesis with significant dysplasia in all cell lineages. Acute myeloid leukemia showed an increase in immature forms, which were highlighted by immunohistochemistry. Reactive extramedullary hematopoiesis showed variability in histologic features. Post-bone marrow transplant and thrombotic thrombocytopenic purpura/hemolytic-uremic syndrome spleens showed extramedullary hematopoiesis with some morphologic features of immaturity, which could simulate chronic myeloproliferative disorder. However, they lacked characteristic immunohistochemical features of neoplastic myeloid disorders such as positivity for CD34 or CD117.

Acute panmyelosis with myelofibrosis: an entity distinct from acute megakaryoblastic leukemia

The WHO criteria for diagnosing acute panmyelosis with myelofibrosis are somewhat distinct from those for acute megakaryoblastic leukemia. However, clinical and hematopathologic findings partially overlap. This has raised questions as to whether these are indeed separate, definable entities. To determine the potential importance of bone marrow biopsy supplemented by immunohistochemistry in distinguishing between these two conditions, we studied 17 bone marrow biopsies of well-characterized cases of acute panmyelosis with myelofibrosis (six cases) and acute megakaryoblastic leukemia (11 cases). We compared blast frequency, reticulin content, CD34 expression, and the degree of megakaryocytic differentiation of the blast cells in these two conditions. Our results demonstrate important differences. Acute panmyelosis with myelofibrosis is characterized by a multilineage myeloid proliferation with a less numerous population of blasts than acute megakaryoblastic leukemia (P<0.01). In the former condition, blasts are always positive with CD34, while in acute megakaryoblastic leukemia they express CD34 in 60% of the cases. The blasts in acute panmyelosis with myelofibrosis only rarely express megakaryocytic antigens. By contrast, acute megakaryoblastic leukemia has a significantly higher proportion of blasts expressing megakaryocytic antigens (P<0.01 with CD42b). Our results confirm that histology supplemented by immunohistochemistry permits the distinction of these conditions in routinely processed bone marrow biopsies.

Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma With Trisomy 12 and Focal Cyclin D1 Expression: A Potential Diagnostic Pitfall

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and mantle cell lymphoma usually are distinctly different in regard to clinical presentation, morphology, immunophenotype, and molecular/genetic findings. In spite of this, select cases may show overlapping characteristics and represent a diagnostic challenge. Cyclin D1 immunohistochemical staining is usually envisioned as a definitive method for resolving this differential diagnosis, with positivity supporting a diagnosis of mantle cell lymphoma. We report a case involving a 58-year-old man with a diagnosis of CLL/SLL for several years. A lymph node excision was performed after increased adenopathy was noted in the cervical region. The excised lymph node showed typical morphologic findings of CLL/SLL, including the presence of characteristic proliferation centers. Cyclin D1 staining, using 3 different antibodies, was present in scattered prolymphocytes and paraimmunoblasts, mostly within proliferation centers. Fluorescence in situ hybridization and conventional cytogenetics demonstrated trisomy 12 and an absence of t(11;14) in lymph node tissue. Focal cyclin D1 expression by immunohistochemistry in nodal CLL/SLL is quite unusual and is discussed as a potential diagnostic pitfall.