Decoding the molecular heterogeneity of pediatric monomorphic post-solid organ transplant lymphoproliferative disorders.

Posttransplant lymphoproliferative disorders (PTLDs) represent a broad spectrum of lymphoid proliferations, frequently associated with Epstein-Barr virus (EBV) infection. The molecular profile of pediatric monomorphic PTLDs (mPTLDs) has not been elucidated, and it is unknown whether they display similar genetic features as their counterpart in adult and immunocompetent (IMC) pediatric patients. In this study, we investigated 31 cases of pediatric mPTLD after solid organ transplantation, including 24 diffuse large B-cell lymphomas (DLBCLs), mostly classified as activated B cell, and 7 cases of Burkitt lymphoma (BL), 93% of which were EBV positive. We performed an integrated molecular approach, including fluorescence in situ hybridization, targeted gene sequencing, and copy number (CN) arrays. Overall, PTLD-BL carried mutations in MYC, ID3, DDX3X, ARID1A, or CCND3 resembling IMC-BL, higher mutational burden than PTLD-DLBCL, and lesser CN alterations than IMC-BL. PTLD-DLBCL showed a very heterogeneous genomic profile with fewer mutations and CN alterations than IMC-DLBCL. Epigenetic modifiers and genes of the Notch pathway were the most recurrently mutated in PTLD-DLBCL (both 28%). Mutations in cell cycle and Notch pathways correlated with a worse outcome. All 7 patients with PTLD-BL were alive after treatment with pediatric B-cell non-Hodgkin lymphoma protocols, whereas 54% of patients with DLBCL were cured with immunosuppression reduction, rituximab, and/or low-dose chemotherapy. These findings highlight the low complexity of pediatric PTLD-DLBCL, their good response to low-intensity treatment, and the shared pathogenesis between PTLD-BL and EBV-positive IMC-BL. We also suggest new potential parameters that could help in the diagnosis and the design of better therapeutic strategies for these patients.

Genomic landscape of follicular lymphoma across a wide spectrum of clinical behaviors.

While some follicular lymphoma (FL) patients do not require treatment or experience prolonged responses, others relapse early, and little is known about genetic alterations specific to patients with a particular clinical behavior. We selected 56 grade 1-3A FL patients according to their need of treatment or timing of relapse: never treated (n = 7), non-relapsed (19), late relapse (14), early relapse or POD24 (11), and primary refractory (5). We analyzed 56 diagnostic and 12 paired relapse lymphoid tissue biopsies and performed copy number alteration (CNA) analysis and next generation sequencing (NGS). We identified six focal driver losses (1p36.32, 6p21.32, 6q14.1, 6q23.3, 9p21.3, 10q23.33) and 1p36.33 copy-neutral loss of heterozygosity (CN-LOH). By integrating CNA and NGS results, the most frequently altered genes/regions were KMT2D (79%), CREBBP (67%), TNFRSF14 (46%) and BCL2 (40%). Although we found that mutations in PIM1, FOXO1 and TMEM30A were associated with an adverse clinical behavior, definitive conclusions cannot be drawn, due to the small sample size. We identified common precursor cells harboring early oncogenic alterations of the KMT2D, CREBBP, TNFRSF14 and EP300 genes and 16p13.3-p13.2 CN-LOH. Finally, we established the functional consequences of mutations by means of protein modeling (CD79B, PLCG2, PIM1, MCL1 and IRF8). These data expand the knowledge on the genomics behind the heterogeneous FL population and, upon replication in larger cohorts, could contribute to risk stratification and the development of targeted therapies.

The ghost tumour revisited. Corticosteroids in primary central nervous system lymphoma: diagnostic, prognostic and therapeutic implications.

OBJECTIVE: The cytolytic effect of corticosteroids on primary central nervous system lymphoma (PCNSL) has established the clinical dogma of avoiding steroid therapy prior to surgery for diagnostic purposes. However, since steroids are very useful during the initial management of intracranial lesions with vasogenic oedema, it was our aim to determine whether they cause a drawback in the diagnosis and prognosis of PCNSL. METHODS: A retrospective cohort study of patients diagnosed with PCNSL between 2000 and 2020 in our tertiary neurosurgical centre. Data on steroid administration, surgery type and complications, haematopathological findings and prognostic factors were compiled. A second cohort was used as a control group to compare the ratio of non-diagnostic biopsies; this series comprised patients who underwent stereotactic brain biopsy for any reason between 2019 and 2020. RESULTS: Forty patients with PCNSL were included in the study, of which 28 (70%) had received steroids before surgery. The use of steroids was more prevalent in patients with poorer performance status at diagnosis. No relevant differences were found in the diagnostic accuracy regardless of steroid exposure (93% under steroids vs 100% without steroids) or type of surgery performed. Furthermore, steroid withdrawal did not seem to augment the diagnostic ratio. The notable diagnostic delay was not influenced by the use of steroids. CONCLUSIONS: Novel imaging and surgical techniques might obviate the need to withhold corticosteroids from patients suffering from PCNSL prior to biopsy. Moreover, when steroids have been given, tapering them and delaying the surgery might not be justified. This could hold relevant therapeutic implications in the early clinical stages.

Clinico-biological features and outcome of patients with splenic marginal zone lymphoma with histological transformation.

We describe 36 patients with splenic marginal zone lymphoma (SMZL) with transformation (SMZL-T), including 15 from a series of 84 patients with SMZL diagnosed at the Hospital Clinic of Barcelona (HCB) and 21 diagnosed with SMZL-T in other centres. In the HCB cohort, the cumulative incidence of transformation at 5 years was 15%. Predictors for transformation were cytopenias, hypoalbuminaemia, complex karyotype (CK) and both the Intergruppo Italiano Linfomi (ILL) and simplified Haemoglobin, Platelet count, lactate dehydrogenase (LDH) and extrahilar Lymphadenopathy (HPLL)/ABC scores (P < 0·05). The only independent predictor for transformation in multivariate analysis was CK [hazard ratio (HR) 4·025, P = 0·05]. Patients with SMZL-T had a significantly higher risk of death than the remainder (HR 3·89, P < 0·001). Of the 36 patients with SMZL-T, one developed Hodgkin lymphoma and 35 a diffuse large B-cell lymphoma, 71% with a non-germinal centre phenotype. The main features were B symptoms, lymphadenopathy, and high serum LDH. CK was observed in 12/22 (55%) SMZL-T and fluorescence in situ hybridisation detected abnormalities of MYC proto-oncogene, basic helix-loop-helix transcription factor (MYC), B-cell leukaemia/lymphoma 2 (BCL2) and/or BCL6 in six of 14 (43%). In all, 21 patients received immunochemotherapy, six chemotherapy, one radiotherapy and three splenectomy. The complete response (CR) rate was 61% and the median survival from transformation was 4·92 years. Predictors for a worse survival in multivariate analysis were high-risk International Prognostic Index (HR 5·294, P = 0·016) and lack of CR (HR 2·67, P < 0·001).

Revised International Prognostic Index and genetic alterations are associated with early failure to R-CHOP in patients with diffuse large B-cell lymphoma.

Relapsed or refractory diffuse large B-cell lymphoma (DLBCL) cases have a poor outcome. Here we analysed clinico-biological features in 373 DLBCL patients homogeneously treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone (R-CHOP), in order to identify variables associated with early failure to treatment (EF), defined as primary refractoriness or relapse within 12 months from diagnosis. In addition to clinical features, mutational status of 106 genes was studied by targeted next-generation sequencing in 111 cases, copy number alterations in 87, and gene expression profile (GEP) in 39. Ninety-seven cases (26%) were identified as EF and showed significantly shorter overall survival (OS). Patients with B symptoms, advanced stage, high levels of serum lactate dehydrogenase (LDH) or ß2-microglobulin, low lymphocyte/monocyte ratio and higher Revised International Prognostic Index (R-IPI) scores, as well as those with BCL2 rearrangements more frequently showed EF, with R-IPI being the most important in logistic regression. Mutations in NOTCH2, gains in 5p15·33 (TERT), 12q13 (CDK2), 12q14·1 (CDK4) and 12q15 (MDM2) showed predictive importance for EF independently from R-IPI. GEP studies showed that EF cases were significantly enriched in sets related to cell cycle regulation and inflammatory response, while cases in response showed over-representation of gene sets related to extra-cellular matrix and tumour microenvironment.

Distinct molecular profile of IRF4-rearranged large B-cell lymphoma.

Pediatric large B-cell lymphomas (LBCLs) share morphological and phenotypic features with adult types but have better prognosis. The higher frequency of some subtypes such as LBCL with IRF4 rearrangement (LBCL-IRF4) in children suggests that some age-related biological differences may exist. To characterize the genetic and molecular heterogeneity of these tumors, we studied 31 diffuse LBCLs (DLBCLs), not otherwise specified (NOS); 20 LBCL-IRF4 cases; and 12 cases of high-grade B-cell lymphoma (HGBCL), NOS in patients ≤25 years using an integrated approach, including targeted gene sequencing, copy-number arrays, and gene expression profiling. Each subgroup displayed different molecular profiles. LBCL-IRF4 had frequent mutations in IRF4 and NF-κB pathway genes (CARD11, CD79B, and MYD88), losses of 17p13 and gains of chromosome 7, 11q12.3-q25, whereas DLBCL, NOS was predominantly of germinal center B-cell (GCB) subtype and carried gene mutations similar to the adult counterpart (eg, SOCS1 and KMT2D), gains of 2p16/REL, and losses of 19p13/CD70. A subset of HGBCL, NOS displayed recurrent alterations of Burkitt lymphoma-related genes such as MYC, ID3, and DDX3X and homozygous deletions of 9p21/CDKN2A, whereas other cases were genetically closer to GCB DLBCL. Factors related to unfavorable outcome were age >18 years; activated B-cell (ABC) DLBCL profile, HGBCL, NOS, high genetic complexity, 1q21-q44 gains, 2p16/REL gains/amplifications, 19p13/CD70 homozygous deletions, and TP53 and MYC mutations. In conclusion, these findings further unravel the molecular heterogeneity of pediatric and young adult LBCL, improve the classification of this group of tumors, and provide new parameters for risk stratification.

Diverse mutations and structural variations contribute to Notch signaling deregulation in paediatric T-cell lymphoblastic lymphoma.

BACKGROUND: T-cell lymphoblastic lymphoma (T-LBL) is an aggressive neoplasm closely related to T-cell acute lymphoblastic leukaemia (T-ALL). Despite their similarities, and contrary to T-ALL, studies on paediatric T-LBL are scarce and, therefore, its molecular landscape has not yet been fully elucidated. Thus, the aims of this study were to characterize the genetic and molecular heterogeneity of paediatric T-LBL and to evaluate novel molecular markers differentiating this entity from T-ALL. PROCEDURE: Thirty-three paediatric T-LBL patients were analyzed using an integrated approach, including targeted next-generation sequencing, RNA-sequencing transcriptome analysis and copy-number arrays. RESULTS: Copy number and mutational analyses allowed the detection of recurrent homozygous deletions of 9p/CDKN2A (78%), trisomy 20 (19%) and gains of 17q24-q25 (16%), as well as frequent mutations of NOTCH1 (62%), followed by the BCL11B (23%), WT1 (19%) and FBXW7, PHF6 and RPL10 genes (15%, respectively). This genetic profile did not differ from that described in T-ALL in terms of mutation incidence and global genomic complexity level, but unveiled virtually exclusive 17q25 gains and trisomy 20 in T-LBL. Additionally, we identified novel gene fusions in paediatric T-LBL, including NOTCH1-IKZF2, RNGTT-SNAP91 and DDX3X-MLLT10, the last being the only one previously described in T-ALL. Moreover, clinical correlations highlighted the presence of Notch pathway alterations as a factor related to favourable outcome. CONCLUSIONS: In summary, the genomic landscape of paediatric T-LBL is similar to that observed in T-ALL, and Notch signaling pathway deregulation remains the cornerstone in its pathogenesis, including not only mutations but fusion genes targeting NOTCH1.

Molecular features of non-anaplastic peripheral T-cell lymphoma in children and adolescents.

Non-anaplasticperipheral T-cell lymphomas (PTCL) are rare tumors in children, adolescents, and young adults (CAYA) with poor prognosis and scarce genetic data. We analyzed lymphoma tissue from 36 patients up to 18 years old with PTCL, not otherwise specified (PTCL-NOS), hepatosplenic T-cell lymphoma, Epstein-Barr virus (EBV)-positive T-lymphoproliferative diseases, subcutaneous panniculitis-like T-cell lymphoma, and other PTCL types. Twenty-three patients (64%) had at least one genetic variant detectable, including TET2, KMT2C, PIK3D, and DMNT3A. TP53 and RHOA variants, commonly found in adults, were not identified. Eight of 20 (40%) CAYA PTCL-NOS had no detectable mutations. The genetic findings suggest that CAYA PTCL differ from adult cases.

Response duration and survival shorten after each relapse in patients with follicular lymphoma treated in the rituximab era.

Follicular lymphoma (FL) is an indolent disease characterized by long survival but frequent relapses. Before the introduction of rituximab, the clinical course of these patients showed a shorter response duration (RD) after each relapse. In this study, we analysed if this pattern of shortened responses remains in patients treated in the rituximab era. We selected 348 patients newly diagnosed with FL in two institutions between 2001 and 2014 that received chemoimmunotherapy. After a median follow-up of 6·3 years, 10-year progression-free and overall survivals were 53% and 72%, respectively. All patients received first-line, 111 second-line and 41 third-line treatments, with a 5-year RD of 62%, 39% and 24%, respectively (P < 0·0001). Variables predicting longer RD after first-line treatment were normal ß2microglobulin, complete remission achievement and maintenance with rituximab. Patients with longer RD after first-line showed significantly longer RD after second-line therapy. Autologous stem-cell transplantation after second-line therapy did not significantly impact RD. Median survival after first, second and third therapies was not reached, 7·6 and 4·8 years, respectively, whereas relative survival with respect to a sex- and age-matched Spanish population, the decrease in the life expectancy at 10 years was 17%, 45% and 79%, respectively. Thus, RD still shortens after each relapse in patients with FL treated in first line with rituximab combinations.

Clinicopathological evaluation of the programmed cell death 1 (PD1)/programmed cell death-ligand 1 (PD-L1) axis in post-transplant lymphoproliferative disorders: association with Epstein-Barr virus, PD-L1 copy number alterations, and outcome.

AIMS: The clinical implications of the programmed cell death 1 (PD1)/programmed cell death-ligand 1 (PD-L1) axis in patients with post-transplant lymphoproliferative disorders are largely unknown, and its association with Epstein-Barr virus (EBV) status and PD-L1 copy number alterations (CNAs) has not been thoroughly studied. METHODS AND RESULTS: PD1/PD-L1 expression was studied in 50 adult post-transplant lymphoproliferative disorders, and the correlations with PD-L1 CNAs, EBV, clinicopathological features and outcome were evaluated. Thirty-seven (74%) cases were classified as diffuse large B-cell lymphoma (DLBCL), nine (18%) cases were classified as polymorphic, and four (8%) cases were classified as classic Hodgkin lymphoma. Thirty-four cases were EBV-positive, with 29 of 34 (85%) having latency II or III, and 15 of 34 (44%) having viral replication. PD-L1 expression in tumour cells and tumour-associated macrophages was observed in 30 (60%) and 37 (74%) cases, respectively. PD1 positivity was seen in 16 (32%) cases. PD-L1 expression was associated with EBV with latency II or III (P = 0.001) and organ rejection (P = 0.04), and, in DLBCL, with non-germinal centre type DLBCL (P < 0.001). Cases with PD-L1-positive tumour cells showed a higher number of PD-L1 CNAs than PD-L1-negative cases (P = 0.001). Patients with EBV/latency III/replication and simultaneous PD-L1 expression showed the worst overall survival (P < 0.001). CONCLUSIONS: The PD1/PD-L1 axis is deregulated in post-transplant lymphoproliferative disorders, with frequent PD-L1 expression and PD1 negativity. PD-L1 expression is associated with EBV latency II or III and PD-L1 CNAs, and probably reflects a proinflammatory tumour microenvironment. The combined analysis of EBV status and PD-L1 expression may help to identify deeply immunosuppressed patients who can benefit from immune reconstitution approaches.

Burkitt-like lymphoma with 11q aberration: a germinal center-derived lymphoma genetically unrelated to Burkitt lymphoma.

Burkitt-like lymphoma with 11q aberration is characterized by pathological features and gene expression profile resembling those of Burkitt lymphoma but lacks the MYC rearrangement and carries an 11q-arm aberration with proximal gains and telomeric losses. Whether this lymphoma is a distinct category or a particular variant of other recognized entities is controversial. To improve the understanding of Burkitt-like lymphoma with 11q aberration we performed an analysis of copy number alterations and targeted sequencing of a large panel of B-cell lymphoma-related genes in 11 cases. Most patients had localized nodal disease and a favorable outcome after therapy. Histologically, they were high grade B-cell lymphoma, not otherwise specified (8 cases), diffuse large B-cell lymphoma (2 cases) and only one was considered as atypical Burkitt lymphoma. All cases had a germinal center B-cell signature and phenotype with frequent LMO2 expression. The patients with Burkitt-like lymphoma with 11q aberration had frequent gains of 12q12-q21.1 and losses of 6q12.1-q21, and lacked common Burkitt lymphoma or diffuse large B-cell lymphoma alterations. Potential driver mutations were found in 27 genes, particularly involving BTG2, DDX3X, ETS1, EP300, and GNA13 However, ID3, TCF3, or CCND3 mutations were absent in all cases. These results suggest that Burkitt-like lymphoma with 11q aberration is a germinal center-derived lymphoma closer to high-grade B-cell lymphoma or diffuse large B-cell lymphoma than to Burkitt lymphoma.

Genome-wide analysis of pediatric-type follicular lymphoma reveals low genetic complexity and recurrent alterations of TNFRSF14 gene.

Pediatric-type follicular lymphoma (PTFL) is a variant of follicular lymphoma (FL) with distinctive clinicopathological features. Patients are predominantly young males presenting with localized lymphadenopathy; the tumor shows high-grade cytology and lacks both BCL2 expression and t(14;18) translocation. The genetic alterations involved in the pathogenesis of PTFL are unknown. Therefore, 42 PTFL (40 males and 2 females; mean age, 16 years; range, 5-31) were genetically characterized. For comparison, 11 cases of conventional t(14:18)(-) FL in adults were investigated. Morphologically, PTFL cases had follicular growth pattern without diffuse areas and characteristic immunophenotype. All cases showed monoclonal immunoglobulin (IG) rearrangement. PTFL displays low genomic complexity when compared with t(14;18)(-) FL (mean, 0.77 vs 9 copy number alterations per case; P <001). Both groups presented 1p36 alterations including TNFRSF14, but copy-number neutral loss of heterozygosity (CNN-LOH) of this locus was more frequently observed in PTFL (40% vs 9%; P =075). TNFRSF14 was the most frequently affected gene in PTFL (21 mutations and 2 deletions), identified in 54% of cases, followed by KMT2D mutations in 16%. Other histone-modifying genes were rarely affected. In contrast, t(14;18)(-) FL displayed a mutational profile similar to t(14;18)(+) FL. In 8 PTFL cases (19%), no genetic alterations were identified beyond IG monoclonal rearrangement. The genetic landscape of PTFL suggests that TNFRSF14 mutations accompanied by CNN-LOH of the 1p36 locus in over 70% of mutated cases, as additional selection mechanism, might play a key role in the pathogenesis of this disease. The genetic profiles of PTFL and t(14;18)(-) FL in adults indicate that these are two different disorders.

Clinico-biological characteristics and outcome of hepatitis C virus-positive patients with diffuse large B-cell lymphoma treated with immunochemotherapy.

Diffuse large B cell lymphoma (DLBCL) patients carrying hepatitis C virus (HCV) have higher risk of treatment toxicity and complications. The aim of this study was to assess the impact of HCV in a series of DLBCL patients treated with immunochemotherapy. 321 patients (161 M/160F; median age, 66 years) diagnosed with de novo DLBCL in a single center between 2002 and 2013 were included. Immunodeficiency-related lymphomas were excluded. HCV+ cases were defined by the presence of IgG anti-HCV. Main clinico-biological characteristics and outcome were analyzed according to the viral status. Two hundred ninety patients were HCV- and 31 HCV+. HCV+ patients were older (median age 71 vs. 64 years, P = 0.03), had more often B symptoms (P = 0.013), spleen (P = 0.003), and liver (P = 0.011) involvement, higher rate of early death (<4 months, P = .001), and shorter overall survival (OS). Eleven HCV+ patients had cirrhosis criteria. HCV+ patients with impaired liver function before or during treatment showed inferior OS. Elevated pre-treatment bilirubin correlated also with higher liver toxicity. In a multivariate analysis that included R-IPI score, serum beta2-microglobulin (ß2m), HCV status, and presence of cirrhosis, only R-IPI, ß2m, and cirrhosis showed independent prognostic impact on OS. The presence of HCV in DLBCL patients entails higher number of complications and early deaths; however, liver impairment and not the hepatitis viral status was the key feature in the outcome of the patients.

Occlusive vasculopathy in human immunodeficiency virus (HIV)-associated vasculitis: unusual clinical and imaging course.

Human immunodeficiency virus (HIV)-associated vasculitis is a rare secondary systemic vasculitis involving small and medium arteries. We report a 42-year-old man with uncontrolled HIV infection presenting with long-lasting abdominal pain. An abdominal CT angiography revealed multiple microaneurysms and stenoses in intrarenal arteries, with involvement of mesenteric and hepatic arteries. HIV-associated vasculitis was diagnosed and glucocorticoids and raltegravir-based antiretroviral therapy were administered with good initial clinical and virological response. Several episodes of acute intestinal ischaemia were later developed requiring bowel resections of which histological examination showed vascular occlusive fibrotic changes without active vasculitic lesions. Vasculitis persisted in remission and intrarenal microaneurysms disappeared.

Definition of MYC genetic heteroclonality in diffuse large B-cell lymphoma with 8q24 rearrangement and its impact on protein expression.

MYC rearrangement can be detected in a subgroup of diffuse large B-cell lymphoma characterized by unfavorable prognosis. In contrast to Burkitt lymphoma, the correlation between MYC rearrangement and MYC protein expression in diffuse large B-cell lymphoma is less clear, as approximately one-third of rearranged cases show negative or low expression by immunohistochemistry. To better understand whether specific characteristics of the MYC rearrangement may influence its protein expression, we investigated 43 de novo diffuse large B-cell lymphoma positive for 8q24 rearrangement by FISH, using 14 Burkitt lymphoma for comparison. Different cell populations (clones), breakpoints (classical vs non-classical FISH patterns), partner genes (IGH vs non-IGH) and immunostaining were detected and analyzed using computerized image systems. In a subgroup of diffuse large B-cell lymphoma, we observed different clones within the same tumor distinguishing the founder clone with MYC rearrangement alone from other subclones, carrying MYC rearrangement coupled with loss/extra copies of derivatives/normal alleles. This picture, which we defined MYC genetic heteroclonality, was found in 42% of cases and correlated to negative MYC expression (P=0.026). Non-classical FISH breakpoints were detected in 16% of diffuse large B-cell lymphoma without affecting expression (P=0.040). Non-IGH gene was the preferential partner of rearrangement in those diffuse large B-cell lymphoma showing MYC heteroclonality (P=0.016) and/or non-classical FISH breakpoints (P=0.058). MYC heteroclonality was not observed in Burkitt lymphoma and all cases had positive MYC expression. Non-classical FISH MYC breakpoint and non-IGH partner were found in 29 and 20% of Burkitt lymphoma, respectively. In conclusion, MYC genetic heteroclonality is a frequent event in diffuse large B-cell lymphoma and may have a relevant role in modulating MYC expression.

The reliability of immunohistochemical analysis of the tumor microenvironment in follicular lymphoma: a validation study from the Lunenburg Lymphoma Biomarker Consortium.

The cellular microenvironment in follicular lymphoma is of biological and clinical importance. Studies on the clinical significance of non-malignant cell populations have generated conflicting results, which may partly be influenced by poor reproducibility in immunohistochemical marker quantification. In this study, the reproducibility of manual scoring and automated microscopy based on a tissue microarray of 25 follicular lymphomas as compared to flow cytometry is evaluated. The agreement between manual scoring and flow cytometry was moderate for CD3, low for CD4, and moderate to high for CD8, with some laboratories scoring closer to the flow cytometry results. Agreement in manual quantification across the 7 laboratories was low to moderate for CD3, CD4, CD8 and FOXP3 frequencies, moderate for CD21, low for MIB1 and CD68, and high for CD10. Manual scoring of the architectural distribution resulted in moderate agreement for CD3, CD4 and CD8, and low agreement for FOXP3 and CD68. Comparing manual scoring to automated microscopy demonstrated that manual scoring increased the variability in the low and high frequency interval with some laboratories showing a better agreement with automated scores. Manual scoring reliably identified rare architectural patterns of T-cell infiltrates. Automated microscopy analyses for T-cell markers by two different instruments were highly reproducible and provided acceptable agreement with flow cytometry. These validation results provide explanations for the heterogeneous findings on the prognostic value of the microenvironment in follicular lymphoma. We recommend a more objective measurement, such as computer-assisted scoring, in future studies of the prognostic impact of microenvironment in follicular lymphoma patients.