Lymphoid blast transformation in an MPN with BCR-JAK2 treated with ruxolitinib: putative mechanisms of resistance.

The basis for acquired resistance to JAK inhibition in patients with JAK2-driven hematologic malignancies is not well understood. We report a patient with a myeloproliferative neoplasm (MPN) with a BCR activator of RhoGEF and GTPase (BCR)-JAK2 fusion with initial hematologic response to ruxolitinib who rapidly developed B-lymphoid blast transformation. We analyzed pre-ruxolitinib and blast transformation samples using genome sequencing, DNA mate-pair sequencing (MPseq), RNA sequencing (RNA-seq), and chromosomal microarray to characterize possible mechanisms of resistance. No resistance mutations in the BCR-JAK2 fusion gene or transcript were identified, and fusion transcript expression levels remained stable. However, at the time of blast transformation, MPseq detected a new IKZF1 copy-number loss, which is predicted to result in loss of normal IKZF1 protein translation. RNA-seq revealed significant upregulation of genes negatively regulated by IKZF1, including IL7R and CRLF2. Disease progression was also characterized by adaptation to an activated B-cell receptor (BCR)-like signaling phenotype, with marked upregulation of genes such as CD79A, CD79B, IGLL1, VPREB1, BLNK, ZAP70, RAG1, and RAG2. In summary, IKZF1 deletion and a switch from cytokine dependence to activated BCR-like signaling phenotype represent putative mechanisms of ruxolitinib resistance in this case, recapitulating preclinical data on resistance to JAK inhibition in CRLF2-rearranged Philadelphia chromosome-like acute lymphoblastic leukemia.

Joint single cell DNA-seq and RNA-seq of gastric cancer cell lines reveals rules of in vitro evolution.

Cancer cell lines are not homogeneous nor are they static in their genetic state and biological properties. Genetic, transcriptional and phenotypic diversity within cell lines contributes to the lack of experimental reproducibility frequently observed in tissue-culture-based studies. While cancer cell line heterogeneity has been generally recognized, there are no studies which quantify the number of clones that coexist within cell lines and their distinguishing characteristics. We used a single-cell DNA sequencing approach to characterize the cellular diversity within nine gastric cancer cell lines and integrated this information with single-cell RNA sequencing. Overall, we sequenced the genomes of 8824 cells, identifying between 2 and 12 clones per cell line. Using the transcriptomes of more than 28 000 single cells from the same cell lines, we independently corroborated 88% of the clonal structure determined from single cell DNA analysis. For one of these cell lines, we identified cell surface markers that distinguished two subpopulations and used flow cytometry to sort these two clones. We identified substantial proportions of replicating cells in each cell line, assigned these cells to subclones detected among the G0/G1 population and used the proportion of replicating cells per subclone as a surrogate of each subclone's growth rate.

Genetic Subtypes of Systemic Anaplastic Large Cell Lymphoma Show Distinct Differences in PD-L1 Expression and Regulatory and Cytotoxic T Cells in the Tumor Microenvironment.

Anaplastic large cell lymphomas (ALCL) encompass several subgroups that differ in their clinical presentation, genetic features, and prognosis. We characterized the genetic subgroups of 74 patients with ALCL and correlated programmed death ligand 1 (PD-L1) protein expression and compared the densities and ratios of FOXP3+ T regulatory cells and CD8+ tumor-infiltrating lymphocytes (TILs) in tumor cells and the immune microenvironment. The subgroups included anaplastic lymphoma kinase (ALK)-positive (ALK+) ALCL and ALK-negative (ALK-) ALCL and DUSP22-rearranged and nonrearranged ALK- ALCL. None of our cases represented the TP63-rearrangement ALK- ALCL subgroup. Our results showed that ALK+ ALCL had a higher expression of PD-L1 in the tumor cells, in contrast to ALK- ALCL, which expressed high PD-L1 in tumor-associated macrophages (TAMs). DUSP22-rearranged ALK- ALCL lacked PD-L1 expression in the tumor cells and instead expressed PD-L1 only in TAMs. There was a significant positive correlation of PD-L1 expression between tumor and TAMs in ALK+ ALCL with a negative correlation in ALK- ALCL. Systemic ALCL subgroups had similar densities of CD8+ tumor-infiltrating lymphocytes and FOXP3 T regulatory cells, but differences were observed in the ratio of CD8/FOXP3. Our results suggest that alterations in tumor microenvironment and immune responses exist among systemic ALCL subgroups and these features may account for different clinical behavior and prognosis.

Technical standards for the interpretation and reporting of constitutional copy-number variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resource (ClinGen).

PURPOSE: Copy-number analysis to detect disease-causing losses and gains across the genome is recommended for the evaluation of individuals with neurodevelopmental disorders and/or multiple congenital anomalies, as well as for fetuses with ultrasound abnormalities. In the decade that this analysis has been in widespread clinical use, tremendous strides have been made in understanding the effects of copy-number variants (CNVs) in both affected individuals and the general population. However, continued broad implementation of array and next-generation sequencing-based technologies will expand the types of CNVs encountered in the clinical setting, as well as our understanding of their impact on human health. METHODS: To assist clinical laboratories in the classification and reporting of CNVs, irrespective of the technology used to identify them, the American College of Medical Genetics and Genomics has developed the following professional standards in collaboration with the National Institutes of Health (NIH)-funded Clinical Genome Resource (ClinGen) project. RESULTS: This update introduces a quantitative, evidence-based scoring framework; encourages the implementation of the five-tier classification system widely used in sequence variant classification; and recommends "uncoupling" the evidence-based classification of a variant from its potential implications for a particular individual. CONCLUSION: These professional standards will guide the evaluation of constitutional CNVs and encourage consistency and transparency across clinical laboratories.

Indolent In Situ B-Cell Neoplasms With MYC Rearrangements Show Somatic Mutations in MYC and TNFRSF14 by Next-generation Sequencing.

Systemic high-grade B-cell lymphomas (HGBCLs) with MYC gene rearrangements are clinically aggressive. In situ lesions with indolent behavior have not been described to date. We have identified 2 cases of in situ B-cell neoplasms with MYC rearrangements (IS-BCN, MYC) occurring, and focally confined to ≤4 lymphoid follicles in otherwise healthy individuals and without clinical progression despite minimal intervention (surgical only). Morphologically similar to systemic HGBCLs, the low power view of these lesions showed a starry sky pattern with numerous mitotic figures. High power imaging demonstrated these cells to be medium-large in size with irregular nuclear contours, immature chromatin, and prominent nucleoli. Immunophenotypically these cells were light chain restricted, positive for CD20, CD10, c-Myc, and dim or negative for BCL2 with a Ki67 proliferative index of >95%. By fluorescence in situ hybridization studies, we detected MYC translocations in these cells but no rearrangements in BCL2 or BCL6. Microdissection of neoplastic cells in these patients followed by targeted next-generation sequencing identified a mutation in MYC, D2N, and an indel in TNFRSF14. Mutations in ID3 or TCF3 were not identified. Although rare, these lesions should be separated from HGBCLs involving follicles but with systemic spread which has been previously described. Unlike systemic lymphomas with MYC gene rearrangements, these in situ B-cell neoplasms with MYC rearrangements did not require systemic therapy and no progression has been seen in either patient beyond 1 year (29 and 16 mo). Our work offers pathologic and biologic insight into the early process of B-cell neoplasia.

Perinatal distress in 1p36 deletion syndrome can mimic hypoxic ischemic encephalopathy.

1p36 deletion syndrome is a well-described condition with a recognizable phenotype, including cognitive impairment, seizures, and structural brain anomalies such as periventricular leukomalacia (PVL). In a large series of these individuals by Battaglia et al., "birth history was notable in 50% of the cases for varying degrees of perinatal distress." Given the potential for perinatal distress, seizures and PVL, we questioned if this disorder has clinical overlap with hypoxic ischemic encephalopathy (HIE). We reviewed the medical records of 69 individuals with 1p36 deletion to clarify the perinatal phenotype of this disorder and determine if there is evidence of perinatal distress and/or hypoxic injury. Our data provides evidence that these babies have signs of perinatal distress. The majority (59% term; 75% preterm) needed resuscitation and approximately 18% had cardiac arrest. Most had abnormal brain imaging (84% term; 73% preterm) with abnormal white matter findings in over half of patients. PVL or suggestion of "hypoxic insult" was present in 18% of term and 45% of preterm patients. In conclusion, individuals with 1p36 deletion have evidence of perinatal distress, white matter changes, and seizures, which can mimic HIE but are likely related to their underlying chromosome disorder.

Acute leukemia in a patient with 15q overgrowth syndrome.

Overgrowth syndromes are rare genetic conditions which present as global or segmental hyperplasia and are sometimes associated with increased risk of malignancy. Trisomy of the terminal portion of 15q which includes the IGFR1 gene, produces a rare overgrowth phenotype that has been termed 15q overgrowth syndrome (15q OGS). Upregulation of IGF1R has long been implicated in oncogenesis of multiple cancer types, including acute leukemias, and has been shown to render cells more susceptible to other transforming events. To date, too few cases of 15q OGS have been reported to identify any cancer predisposition. We present a case of a 34-year-old female with intellectual disability, macrocephaly, and subtle dysmorphic features who was diagnosed with mixed phenotype acute leukemia (lymphoid and myeloid). Prior to initiation of therapy she was referred to medical genetics for further evaluation and was identified as having a chromosomal translocation resulting in a partial trisomy of chromosome 15q, consistent with 15q OGS. A review of the literature for cases of malignancy in individuals with increased copy number of 15q revealed only one other reported patient. Given the small number of reported individuals, we cannot rule out an increased risk of cancer associated with this chromosomal overgrowth syndrome. Although concerns have been raised regarding treatment feasibility in the setting of chromosomal disorders, the reported patient underwent successful treatment with allogeneic hematopoietic stem-cell transplant.

Immune checkpoint blockade as a potential therapeutic strategy for undifferentiated malignancies.

Undifferentiated malignancies (UMs) encompass a diverse set of aggressive tumors that pose not only a diagnostic challenge but also a challenge for clinical management. Most tumors in this category are currently treated empirically with nonspecific chemotherapeutic agents that yield extremely poor clinical response. Given that UMs are inherently genetically unstable neoplasms with the potential for immune dysregulation and increased neoantigen production, they are likely to be particularly amenable to immune checkpoint inhibitors, which target programmed cell death protein 1 (PD-1) or its ligands, PD-L1 and PD-L2, to promote T-cell antitumor activity. Aberrant expression of PD-L1 and, more recently, chromosomal 9p24.1/CD274(PD-L1)/PDCD1LG2(PD-L2) alterations can be used as biomarkers to predict responsiveness to checkpoint inhibitors. Here we evaluated 93 cases previously diagnosed as an "undifferentiated" malignancy and found that 56% (52/93) of UMs moderately to strongly express PD-L1 by immunohistochemistry (IHC). Concurrent CD274(PD-L1) and PDCD1LG2(PD-L2) fluorescence in situ hybridization (FISH) was performed on 24 of these cases and demonstrates a genetic gain at both loci in 62.5% of UMs. Genetic alterations at the CD274(PD-L1) and PDCD1LG2(PD-L2) loci were found to be completely concordant by FISH. Overall, we found that a significant proportion of UMs express PD-L1 and provide molecular support for using checkpoint inhibitors as a treatment approach for this class of tumors.

A Clinicopathologic and Molecular Analysis of 34 Mediastinal Germ Cell Tumors Suggesting Different Modes of Teratoma Development.

Mediastinal teratomas are enigmatic; those in children and women are almost invariably benign but in men they may be benign or malignant. There are few data on the chromosome 12p status of mediastinal germ cell tumors (GCT), whereas increased 12p copy number is virtually uniform in malignant testicular GCTs. We therefore studied chromosome 12p copy number in 34 diverse mediastinal GCTs and correlated the results with morphology and follow-up to gain insight into possible pathogenesis. Four prepubertal (below 12 y) children (3 females and 1 male), 7 postpubertal females (14 to 52 y) and 6 postpubertal males (12 to 40 y old) had pure, previously untreated teratomas; 15 were mature and 2 had low-grade immaturity. All lacked 12p copy number increase and cytologic atypia, and most (14/17) showed organoid morphology. On follow-up of 16, 1 died of postoperative complications and the remaining 15 were disease free (1 to 119 mo, mean: 39 mo). Eight postpubertal males (19 to 44 y old) had pure teratomas in postchemotherapy resections; 5/8 showed 12p copy number increase. All 8 had distinct cytologic atypia, with organoid morphology in 3. On follow-up, 6 were disease free after surgical resection (1.5 to 94 mo, mean 38 mo); 1 died of disease at 14.5 months, and 1 was alive with metastases at 176 months. Two postpubertal patients, 1 male (29 y) and 1 female (31 y), had teratoma with secondary somatic-type malignancies, with positive 12p copy number increase in the former but not the latter. The man's tumor occurred after chemotherapy and was a nonorganoid teratoma with primitive neuroectodermal tumor and malignant glioma; the woman's was a previously untreated organoid teratoma with an undifferentiated carcinoma component. The man died of disease (16 mo) and the woman was alive with metastases (27 mo). Seven patients had resections for mixed GCTs (4) or pure nonteratomatous tumors, all after chemotherapy; 5/7 had positive 12p copy number increase. The teratoma component of the 2 cases having one showed distinct cytologic atypia and lacked organoid morphology. On follow-up, 1 died of disease (5 mo), 2 were alive with disease (1, 1.5 mo), 3 were disease free (1 to 43 mo; mean: 18 mo), and 1 was alive with unknown status (31 mo). Our results support that mediastinal teratomas likely develop from 2 separate pathways. Those in children, women and some men arise as pure neoplasms from a nontransformed precursor cell and, therefore, lack 12p copy number increase, show no cytologic atypia, often have organoid morphology and are benign. Common 12p copy number increase, uniform atypia, infrequent organoid structures and malignant behavior support that pure teratomas after chemotherapy in postpubertal males derive from a malignantly transformed precursor cell. Interestingly, we identified organoid pancreatic differentiation only in the benign group and neuroglia more commonly in the malignant teratomas.

An analysis of blastic plasmacytoid dendritic cell neoplasm with translocations involving the MYC locus identifies t(6;8)(p21;q24) as a recurrent cytogenetic abnormality.

AIMS: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm with leukaemic features and frequent skin involvement. Translocations involving the MYC locus have been recently identified as recurrent cytogenetic abnormalities in this entity. The aim of this study was to assess the clinicopathological, immunophenotypic and genetic features in MYC-rearranged BPDCN cases. METHODS AND RESULTS: Pathology archives from six major institutes were queried for cases of BPDCN with 8q24 MYC translocations, and two cases were identified. A literature review identified 14 cases. Clinicopathological features, immunophenotype and cytogenetic and molecular data were reviewed. In these 16 MYC-rearranged cases, the median age at diagnosis was 70.5 years, and there was a male predominance. Whereas all cases showed marrow involvement, skin lesions (62.5%) and lymphadenopathy (50%) were variably seen. The median survival was 11 months. The median percentage of blasts in peripheral blood was 9%. All cases showed expression of CD4, with 10 of 16 being positive for CD56. HLA-DR, CD123, TCL1 and CD303 were positive in all cases tested. Cytogenetic analysis revealed a single recurrent translocation partner of MYC at 6p21 in 11 cases (69%), whereas four cases showed different MYC translocation partners (2p12, Xq24, 3p25, and 14q32). Interestingly, the group of patients with t(6;8)(p21;q24) showed an older median age at diagnosis (74 years) and a remarkably shorter median survival (3 months). CONCLUSIONS: Translocations involving the 8q24 MYC locus more frequently manifest as t(6;8)(p21;q24), and, given its association with specific clinicopathological features suggesting even more aggressive behaviour, t(6;8)(p21;q24) indicate a genetically defined subgroup within BPDCN.

Investigating human placentation and pregnancy using first trimester chorionic villi.

Chorionic villus sampling (CVS), routinely used for prenatal diagnosis of cytogenetic disorders, also possesses great potential for the study of placentation. To better understand villus biology, human placentation, and how these relate to pregnancy outcomes, we examined the morphology and transcriptomes of villi obtained via CVS from 10 to 14 weeks of pregnancy and correlated these with pregnancy attributes and clinical outcomes. First, we established a morphological scoring system based on three main villus features: branching, budding and vascularization. We then tested whether morphology scores were predictive of pregnancy attributes and clinical outcomes. Finally, we used RNA sequencing to assess the transcriptional basis of villus morphology and tested the hypothesis that gene expression may predict pregnancy outcomes. We demonstrate that villus morphology varies tremendously between patients, irrespective of gestational age, and that transcriptional differences are highly predictive of villus morphology. We show that pre-eclampsia markers are associated with villi with low morphology scores. Additionally, we identify SVEP1 as a possible biomarker for defining gestational age. Overall, chorionic villi in the first trimester remain one of the few means to correlate placental function with pregnancy outcome and these samples are a valuable and increasingly rare resource.

A novel TRIP11-FLT3 fusion in a patient with a myeloid/lymphoid neoplasm with eosinophilia.

FLT3 fusions are associated with myeloid and lymphoid neoplasms with eosinophilia. We describe a patient presenting with clinicopathologic features of both chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) and systemic mastocytosis (SM). The bone marrow demonstrated a myeloproliferative neoplasm with eosinophilia and aggregates of atypical mast cells. Cytogenetic analysis revealed a t(13;14)(q12;q32), which was subsequently molecularly characterized as a novel TRIP11-FLT3 rearrangement. A KIT D816V mutation was also identified. The patient rapidly transformed to T-lymphoblastic leukemia/lymphoma and expired shortly after diagnosis. This is the fifth FLT3 fusion gene described in the literature; the presence of both myeloid and lymphoid neoplasms implicates involvement of an early hematopoietic progenitor by rearranged FLT3. We suggest that leukemias and lymphomas with FLT3 fusion genes exhibit similar clinicopathologic features to, and should be included in, the WHO category of "Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1, or with PCM1-JAK2."

Diagnostic cytogenetic testing following positive noninvasive prenatal screening results: a clinical laboratory practice resource of the American College of Medical Genetics and Genomics (ACMG).

Disclaimer: ACMG Clinical Laboratory Practice Resources are developed primarily as an educational tool for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these practice resources is voluntary and does not necessarily assure a successful medical outcome. This Clinical Laboratory Practice Resource should not be considered inclusive of all proper procedures and tests or exclusive of other procedures and tests that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, the clinical laboratory geneticist should apply his or her own professional judgment to the specific circumstances presented by the individual patient or specimen. Clinical laboratory geneticists are encouraged to document in the patient's record the rationale for the use of a particular procedure or test, whether or not it is in conformance with this Clinical Laboratory Practice Resource. They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures.Noninvasive prenatal screening (NIPS) using cell-free DNA has been rapidly adopted into prenatal care. Since NIPS is a screening test, diagnostic testing is recommended to confirm all cases of screen-positive NIPS results. For cytogenetics laboratories performing confirmatory testing on prenatal diagnostic samples, a standardized testing algorithm is needed to ensure that the appropriate testing takes place. This algorithm includes diagnostic testing by either chorionic villi sampling or amniocentesis samples and encompasses chromosome analysis, fluorescence in situ hybridization, and chromosomal microarray.

Independent Prognostic Significance of Monosomy 17 and Impact of Karyotype Complexity in Monosomal Karyotype/Complex Karyotype Acute Myeloid Leukemia: Results from Four ECOG-ACRIN Prospective Therapeutic Trials.

The presence of a monosomal karyotype (MK+) and/or a complex karyotype (CK+) identifies subcategories of AML with poor prognosis. The prognostic significance of the most common monosomies (monosomy 5, monosomy 7, and monosomy 17) within MK+/CK+AML is not well defined. We analyzed data from 1,592 AML patients age 17-93 years enrolled on ECOG-ACRIN therapeutic trials. The majority of MK+ patients (182/195; 93%) were MK+/CK+ with 87% (158/182) having ≥5 clonal abnormalities (CK≥5). MK+ patients with karyotype complexity ≤4 had a median overall survival (OS) of 0.4y compared to 1.0y for MK- with complexity ≤4 (p<0.001), whereas no OS difference was seen in MK+vs. MK- patients with CK≥5 (p=0.82). Monosomy 5 (93%; 50/54) typically occurred within a highly complex karyotype and had no impact on OS (0.4y; p=0.95). Monosomy 7 demonstrated no impact on OS in patients with CK≥5 (p=0.39) or CK≤4 (p=0.44). Monosomy 17 appeared in 43% (68/158) of CK≥5 patients and demonstrated statistically significant worse OS (0.4y) compared to CK≥5 patients without monosomy 17 (0.5y; p=0.012). Our data suggest that the prognostic impact of MK+is limited to those with less complex karyotypes and that monosomy 17 may independently predict for worse survival in patients with AML.

Commentary on the decision of the American Board of Medical Genetics and Genomics to create a 24-month specialty of Laboratory Genetics and Genomics.

Genet Med 19 3, 294-296.

Two cases of histiocytic sarcoma with BCL2 translocations and occult or subsequent follicular lymphoma.

Histiocytic sarcoma is rare and difficult to distinguish from histologic mimics such as myeloid sarcoma due to its relatively nonspecific immunoprofile. A subset of histiocytic sarcomas are clonally related to synchronous or metachronous follicular lymphomas. Interestingly, the histiocytic tumor component has been shown to harbor BCL2 gene translocations that are identical to those found in the lymphoma. We present one case of histiocytic sarcoma and initially occult follicular lymphoma in which detection of a BCL2 gene translocation helped support the diagnosis. We also provide follow-up regarding a previously published case of histiocytic sarcoma with IGH/BCL2 fusion gene in which the patient subsequently developed follicular lymphoma and, later, diffuse large B-cell lymphoma. Our findings suggest that BCL2 gene translocations are a recurrent feature of a distinct subset of histiocytic sarcomas that are associated with follicular lymphoma; the follicular lymphoma component may be clinically occult at the time of diagnosis. Testing for an IGH/BCL2 translocation should be considered in the diagnostic workup of difficult-to-characterize neoplasms with histiocytic/monocytic morphology and immunoprofile.

Section E6.1-6.4 of the ACMG technical standards and guidelines: chromosome studies of neoplastic blood and bone marrow-acquired chromosomal abnormalities.

DISCLAIMER: These American College of Medical Genetics and Genomics standards and guidelines are developed primarily as an educational resource for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these standards and guidelines is voluntary and does not necessarily ensure a successful medical outcome. These standards and guidelines should not be considered inclusive of all proper procedures and tests or exclusive of other procedures and tests that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, the clinical laboratory geneticist should apply his or her own professional judgment to the specific circumstances presented by the individual patient or specimen. Clinical laboratory geneticists are encouraged to document in the patient's record the rationale for the use of a particular procedure or test, whether or not it is in conformance with these standards and guidelines. They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures.Cytogenetic analyses of hematological neoplasms are performed to detect and characterize clonal chromosomal abnormalities that have important diagnostic, prognostic, and therapeutic implications. At the time of diagnosis, cytogenetic abnormalities assist in the diagnosis of such disorders and can provide important prognostic information. At the time of relapse, cytogenetic analysis can be used to confirm recurrence of the original neoplasm, detect clonal disease evolution, or uncover a new unrelated neoplastic process. This section deals specifically with the standards and guidelines applicable to chromosome studies of neoplastic blood and bone marrow-acquired chromosomal abnormalities. This updated Section E6.1-6.4 has been incorporated into and supersedes the previous Section E6 in Section E: Clinical Cytogenetics of the 2009 Edition (Revised 01/2010), American College of Medical Genetics and Genomics Standards and Guidelines for Clinical Genetics Laboratories.Genet Med 18 6, 635-642.

Isolated Follicles Enriched for Centroblasts and Lacking t(14;18)/BCL2 in Lymphoid Tissue: Diagnostic and Clinical Implications.

We sought to address the significance of isolated follicles that exhibit atypical morphologic features that may be mistaken for lymphoma in a background of reactive lymphoid tissue. Seven cases that demonstrated centroblast-predominant isolated follicles and absent BCL2 staining in otherwise-normal lymph nodes were studied. Four of seven cases showed clonal B-cell proliferations amid a polyclonal B cell background; all cases lacked the IGH-BCL2 translocation and BCL2 protein expression. Although three patients had invasive breast carcinoma at other sites, none were associated with systemic lymphoma up to 44 months after diagnosis. The immunoarchitectural features of these highly unusual cases raise the question of whether a predominance of centroblasts and/or absence of BCL2 expression could represent a precursor lesion or atypical reactive phenomenon. Differentiating such cases from follicular lymphoma or another mimic is critical, lest patients with indolent proliferations be exposed to unnecessarily aggressive treatment.

An analysis of MYC and EBV in diffuse large B-cell lymphomas associated with angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified.

Composite diffuse large B-cell lymphomas (DLBCLs) with peripheral T-cell lymphomas (PTCLs) are rare co-occurrences with poorly understood pathologic features. Herein, we describe 15 distinct cases of DLBCL occurring in association with PTCL, including angioimmunoblastic T-cell lymphoma (AITL; n = 12) and PTCL, not otherwise specified (n = 3). Sheets of large B cells were seen in all cases, with Hodgkin/Reed-Sternberg-like (HRS-L) cells present in 6 cases. When compared to cases of AITL without DLBCL, HRS-L cells were more frequently seen in cases of AITL with DLBCL (P = .02). Epstein-Barr virus (EBV) expression was seen in 10 of 15 cases, and in those with HRS-L cells, EBV expression was detected invariably in at least a subset of the HRS-L cells. MYC gene rearrangements were consistently absent, although 6 of the 10 cases showed MYC overexpression by immunohistochemistry in the neoplastic B cells; a frequency significantly increased compared to other cases of DLBCL not associated with a T-cell lymphoma: 29 of 166 (P = .005). In addition, when MYC was overexpressed in DLBCL, it was also weakly present in the HRS-L cells. The increased and frequent morphologic presence of HRS-L cells in association with this composite lymphoma raises a possible link between their occurrence and DLBCLs in PTCLs; furthermore, the frequent detection of MYC protein expression and EBV infection in these cases suggests a possible role of these pathways in B-cell lymphomagenesis.