Parallel testing of liquid biopsy (ctDNA) and tissue biopsy samples reveals a higher frequency of EZH2 mutations in follicular lymphoma.

BACKGROUND: Recent genomic studies revealed enhancer of zeste homolog 2 (EZH2) gain-of-function mutations, representing novel therapeutic targets in follicular lymphoma (FL) in around one quarter of patients. However, these analyses relied on single-site tissue biopsies and did not investigate the spatial heterogeneity and temporal dynamics of these alterations. OBJECTIVES: We aimed to perform a systematic analysis of EZH2 mutations using paired tissue (tumor biopsies [TB]) and liquid biopsies (LB) collected prior to treatment within the framework of a nationwide multicentric study. METHODS: Pretreatment LB and TB samples were collected from 123 patients. Among these, 114 had paired TB and LB, with 39 patients characterized with paired diagnostic and relapse samples available. The EZH2 mutation status and allele burden were assessed using an in-house-designed, highly sensitive multiplex droplet digital PCR assay. RESULTS: EZH2 mutation frequency was found to be 41.5% in the entire cohort. In patients with paired TB and LB samples, EZH2 mutations were identified in 37.8% of the patients with mutations exclusively found in 5.3% and 7.9% of TB and LB samples, respectively. EZH2 mutation status switch was documented in 35.9% of the patients with paired diagnostic and relapse samples. We also found that EZH2 wild-type clones may infiltrate the bone marrow more frequently compared to the EZH2 mutant ones. CONCLUSION: The in-depth spatio-temporal analysis identified EZH2 mutations in a considerably higher proportion of patients than previously reported. This expands the subset of FL patients who most likely would benefit from EZH2 inhibitor therapy.

Comparison of Follicular Helper T-Cell Markers with the Expression of the Follicular Homing Marker CXCR5 in Peripheral T-Cell Lymphomas-A Reappraisal of Follicular Helper T-Cell Lymphomas.

Peripheral T-cell lymphomas (PTCLs) expressing multiple follicular T helper (TFH) cell-related antigens are now classified as TFH lymphomas (TFHL), including angioimmunoblastic, follicular, and not otherwise specified (NOS) types. CXCR5 is the TFH cell-defining chemokine receptor that, together with its ligand CXCL13, plays a critical role in the development of follicles and the positioning of TFH and B cells within follicles. A comprehensive immunomorphologic study was performed to investigate the expression pattern of CXCR5 in a large cohort of nodal PTCLs, particularly those with a TFH cell phenotype, and to compare its expression with six other TFH cell-related antigens. We found that CXCR5 is widely expressed in neoplastic TFH cells, except in TFHL-NOS, and represents a specific marker of this lymphoma entity. Our results suggest that CXCR5 directs the distribution of neoplastic T cells in the affected lymph nodes and may influence the formation of the pathognomic pathological FDC network.

Syntaxin 1: A Novel Robust Immunophenotypic Marker of Neuroendocrine Tumors.

Considering the specific clinical management of neuroendocrine (NE) neoplasms (NENs), immunohistochemistry (IHC) is required to confirm their diagnosis. Nowadays, synaptophysin (SYP), chromogranin A (CHGA), and CD56 are the most frequently used NE immunohistochemical markers; however, their sensitivity and specificity are less than optimal. Syntaxin 1 (STX1) is a member of a membrane-integrated protein family involved in neuromediator release, and its expression has been reported to be restricted to neuronal and NE tissues. In this study, we evaluated STX1 as an immunohistochemical marker of NE differentiation. STX1, SYP, CHGA, and CD56 expression was analyzed in a diverse series of NE tumors (NETs), NE carcinomas (NECs), and non-NE tumors. All but one (64/65; 98%) NETs and all (54/54; 100%) NECs revealed STX1 positivity in at least 50% of the tumor cells. STX1 showed the highest sensitivity both in NETs (99%) and NECs (100%) compared to CHGA (98% and 91%), SYP (96% and 89%), and CD56 (70% and 93%), respectively. A wide variety of non-NE tumors were tested and found to be uniformly negative, yielding a perfect specificity. We established that STX1 is a robust NE marker with an outstanding sensitivity and specificity. Its expression is independent of the site and grade of the NENs.

A novel target for the promotion of dermal wound healing: Ryanodine receptors.

Ryanodine receptors have an important role in the regulation of intracellular calcium levels in the nervous system and muscle. It has been described that ryanodine receptors influence keratinocyte differentiation and barrier homeostasis. Our goal was to examine the role of ryanodine receptors in the healing of full-thickness dermal wounds by means of in vitro and in vivo methods. The effect of ryanodine receptors on wound healing, microcirculation and inflammation was assessed in an in vivo mouse wound healing model, using skin fold chambers in the dorsal region, and in HaCaT cell scratch wound assay in vitro. SKH-1 mice were subjected to sterile saline (n = 36) or ryanodine receptor agonist 4-chloro-m-cresol (0.5 mM) (n = 42) or ryanodine receptor antagonist dantrolene (100 µM) (n = 42). Application of ryanodine receptor agonist 4-chloro-m-cresol did not influence the studied parameters significantly, whereas ryanodine receptor antagonist dantrolene accelerated the wound closure. Inhibition of the calcium channel also increased the vessel diameters in the wound edges during the process of healing and increased the blood flow in the capillaries at all times of measurement. Furthermore, application of dantrolene decreased xanthine-oxidoreductase activity during the inflammatory phase of wound healing. Inhibition of ryanodine receptor-mediated effects positively influence wound healing. Thus, dantrolene may be of therapeutic potential in the treatment of wounds.

Spontaneous pathological complete regression of high-grade triple-negative breast cancer with axillary metastasis.

We report on a breast carcinoma with medullary features diagnosed by core needle biopsy in a 72-year-old woman. Both the primary tumour and its fine needle aspiration-proven, rapidly growing axillary metastasis regressed completely in less than 2 months, by the time surgery was performed. The biopsy of the primary tumour demonstrated a dense stromal infiltrate of CD8+/granzyme B+ activated cytotoxic T-cells suggestive of a robust antitumour immune response. Paradoxically, both tumour cells and tumour infiltrating immune cells demonstrated a diffuse PD-L1 expression, revealing that antitumour immune response has the ability to spontaneously overcome inhibitory mechanisms induced by cancerous growth.

[Rapidly progressive proliferative glomerulonephritis with monoclonal immunoglobulin G deposits despite the mild histological changes. Case report]. / Enyhe szövettani eltérések ellenére gyors progressziójú proliferativ glomerulonephritis monoklonális immunglobulin-G-depozitumokkal.

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits is characterized by granular deposits of monoclonal IgG; histologically it has typically a membranoproliferative or endocapillary pattern, and seen electronmicroscopically there are dense deposits without substructure. Here, we present the case of a 62-year-old Caucasian woman who was admitted with rapidly progressive kidney failure. The patient's status, the laboratory and imaging examinations did not support prerenal, postrenal and - among the intrinsic causes - vascular and tubulointerstitial origin. The proteinuria and dysmorphic microhematuria suggested rapidly progressive glomerulonephritis. Tests for anti-neutrophil cytoplasmic antibodies, anti-glomerular basement membrane, antinuclear antibodies and cryoglobulins were negative, the C3 and C4 levels were normal. The biopsy evaluation diagnosed proliferative glomerulonephritis with monoclonal IgG deposits because of mesangial granular deposits of IgG3-kappa, C3, and C1q, and ultrastructurally electron-dense deposits (incidence in our adult native kidney biopsy series: 0.18%). 31 glomeruli were assessed histologically. 29 glomeruli displayed mild mesangial hypercellularity, 2 glomeruli were globally sclerotic. Crescents were not observed. Mild arteriolar hyalinosis, interstitial fibrosis and tubular atrophy accompanied the glomerular alterations. In the postbiopsy evaluation, paraprotein or multiple myeloma was not detected. Despite the mild histological findings, the kidney failure progressed, and hemodialysis had to be started two weeks after the biopsy. Steroids, cyclophosphamide and rituximab did not affect her kidney function, and she remained on hemodialysis during the follow-up of 39 months. This report presents for the first time proliferative glomerulonephritis with monoclonal IgG deposits as the possible cause of rapidly progressive nephritic syndrome in the absence of pronounced glomerular proliferative, sclerotic or tubulointerstitial lesions. Orv Hetil. 2018; 159(38): 1567-1572.

[What should we know about cardiac amyloidosis? From clinical signs to treatment]. / Mit kell tudnunk a cardialis amyloidosisról? A tünettantól a kezelésig.

Systemic amyloidosis is a rare disease, in which the heart involvement is rather frequent and determines survival remarkably. Regarding the disease and organ involvement, new diagnostic procedures help to establish the diagnosis and to start the adequate treatment as soon as possible. Cardiac involvement is more likely to be characterised by monoclonal immunglobulin free light chain (AL amyloidosis) type and transthyretin type. In case of AL amyloidosis, heart involvement can lead to serious consequences. Biomarker assessments for cardiac function are important to determine disease severity at the beginning and to measure response to the treatment. In case of amyloidosis, the incidence of the heart involvement grows with age. The prevalence is not known exactly, but probably there are more cases than recognised. The authors present the clinical signs and diagnostic methods, emphasizing the importance of the cardiac examination methods. Orv Hetil. 2017; 158(46): 1811-1818.

[Incidence and treatment of extranodal natural killer/T-cell lymphoma nasal type. Hungarian experiences]. / Nasalis típusú extranodalis natural killer T-sejtes lymphoma hazai elofordulása és kezelésével szerzett tapasztalatok.

INTRODUCTION: Extranodal natural killer/T (NK/T) cell lymphoma, nasal type (ENKTL) represents a rare subtype of T-cell lymphomas with aggressive clinical behavior according to WHO 2016 classification. AIM: ENKTL has distinctive geographic distribution with higher incidence in Asia and Latin America (10% of all non-Hodgkin lymphoma cases), than in Europe and North America (<1%). ENKTL tipically origins from nasopharynx and upper aerodigestive tract. Anthracycline-based chemotherapy regimens are largely ineffective in the treatment of ENKTL. METHOD: Our aims were to evaluate the incidence and treatment strategies of ENKTL patients in Hungarian Haematological Centres between 2003 and 2015. Altogether 20 patients with ENKTL were treated in the 4 haematological hospitals (male:female ratio 12:8, with median 49.5 years of age). RESULTS: Ten patients had localized (stage I-II) disease at the time of the diagnosis. Seventeen patients were treated with chemotherapy (11/CHOP, CHOP-like, 2/HyperCVAD, 1/ProMACECytaBom, 1/SMILE, 2/others), which was completed with involved-field radiation therapy (IFRT) (40-46 Gy) in 6 cases were used. After first-line therapy 9 patients achieved complete remission (CR), 3 patients had partial remission (PR), 3 patients had progressive disease (PD), and 2 patients had stable disease (SD). Median follow-up was 32 (3-113) months. Five patients received second-line therapy for progressive or recurrent disease [2/DHAP, 1/VIM, 1/HyperCVAD, 1/ProMACECytaBom]. None of the patients achieved CR after second-line therapy. Two patients have undergone autologous hematopoietic stem cell transplantation (HSCT) after the first CR. CONCLUSION: ENKTL treatment is more effective with nonanthracycline-containing regimens. L-asparaginase containing chemotherapy and concurrent or sequential chemo-radiotherapy improves survival and CR rates. Orv Hetil. 2017; 158(41): 1635-1641.

Platelet-derived growth factor receptor ß (PDGFRß) immunohistochemistry highlights activated bone marrow stroma and is potentially predictive for fibrosis progression in prefibrotic myeloproliferative neoplasia.

AIMS: Myelofibrosis is the result of aberrant stromal activity which is determined routinely by reticulin staining in bone marrow biopsies. As matrix fibres are the product of activated fibroblasts, we analysed fibre accumulation compared to stromal cell activity during myelofibrosis progression using the fibroblast activation marker platelet-derived growth factor receptor ß (PDGFRß) by immunohistochemistry. METHODS AND RESULTS: Initial and follow-up bone marrow biopsies from 84 patients with myeloproliferative neoplasia, including 55 cases with primary myelofibrosis, were evaluated from five haematopathology centres. The stromal mass was measured by conventional reticulin staining [myelofibrosis (MF) grade, 0-3] and PDGFRß-positive cells using a novel PDGFRß scoring system (0-3). Results were correlated for prediction of progression. The MF grade and the PDGFRß score showed excellent correlation (Spearman's r = 0.83, P < 0.0001). Elevated PDGFRß scores (higher than MF-grade) predicted myelofibrosis progression in total with 43% sensitivity and 57% specificity, and short-term (within 1 year) progression with 82% sensitivity and 53% specificity. Progression of prefibrotic disease to manifest myelofibrosis could be forecast with 90% sensitivity and 75% specificity. CONCLUSION: PDGFRß highlights stromal cell activation in marrow fibrosis, which is closely related to matrix accumulation, indicating a direct clinical impact especially in prefibrotic myeloproliferative disorders.

[Large granular lymphocytic leukemia. A rare disease with personalized treatment options]. / Nagy, granulált citoplazmájú lymphocytás leukaemia. Ritka betegség, személyre szabott kezelési lehetoségekkel.

INTRODUCTION: Large granular lymphocyte leukemia is rare, mainly chronic disease. The most common complication is neutropenia, but other immune-mediated cytopenia may also occur. There are no unified treatment recommendations and initiation of treatment mainly depends on the severity of the symptoms. AIM: The aim of the authors was to analyze the main steps of the diagnosis and the necessity and outcome of treatment in their patients diagnosed with large granular lymphocyte leukaemia. METHOD: The authors retrospectively analyzed the data of 17 large granular lymphocyte leukemia patients. RESULTS: Of the 17 patients, 7 patients required treatment because of transfusion dependent anemia (4 patients) or neutropenia (3 patients). In 4 patients corticosteroid was given (supplemented with cyclosporine in one patients), while the other patients received anti-CD52 (one patient), low dose methotrexate (one patient) and combined chemotherapy (one patient). Five patients achieved partial response, and two patients died in sepsis. CONCLUSIONS: In this cohort only a smaller proportion of patients required therapy. Immunosuppression can be successful, but the effect in most cases was temporary. The most serious complication was sepsis, which is associated with a significant risk of mortality in cases with neutropenia.

1,25-dihydroxyvitamin D3 is an autonomous regulator of the transcriptional changes leading to a tolerogenic dendritic cell phenotype.

Activation of vitamin D receptor (VDR) by 1,25-dihydroxyvitamin D(3) (1,25-vitD) reprograms dendritic cells (DC) to become tolerogenic. Previous studies suggested that 1,25-vitD could inhibit the changes brought about by differentiation and maturation of DCs. Underpinning the described phenotypic and functional alterations, there must be 1,25-vitD-coordinated transcriptional events. However, this transcriptional program has not been systematically investigated, particularly not in a developmental context. Hence, it has not been explored how 1,25-vitD-regulated genes, particularly the ones bringing about the tolerogenic phenotype, are connected to differentiation. We conducted global gene expression analysis followed by comprehensive quantitative PCR validation to clarify the interrelationship between 1,25-vitD and differentiation-driven gene expression patterns in developing human monocyte-derived and blood myeloid DCs. In this study we show that 1,25-vitD regulates a large set of genes that are not affected by differentiation. Interestingly, several genes, impacted both by the ligand and by differentiation, appear to be regulated by 1,25-vitD independently of the developmental context. We have also characterized the kinetics of generation of 1,25-vitD by using three early and robustly regulated genes, the chemokine CCL22, the inhibitory receptors CD300LF and CYP24A1. We found that monocyte-derived DCs are able to turn on 1,25-vitD sensitive genes in early phases of differentiation if the precursor is present. Our data collectively suggest that exogenous or endogenously generated 1,25-vitD regulates a large set of its targets autonomously and not via inhibition of differentiation and maturation, leading to the previously characterized tolerogenic state.

Syntaxin-1 and Insulinoma-Associated Protein 1 Expression in Breast Neoplasms with Neuroendocrine Features.

Introduction: A subset of breast neoplasia is characterized by features of neuroendocrine differentiation. Positivity for Neuroendocrine markers by immunohistochemistry is required for the diagnosis. Sensitivity and specificity of currently used markers are limited; based on the definitions of WHO Classification of Tumours, 5th edition, about 50% of breast tumors with features of neuroendocrine differentiation express chromogranin-A and 16% express synaptophysin. We assessed the applicability of two novel markers, syntaxin-1 and insulinoma-associated protein 1 (INSM1) in breast carcinomas. Methods: Hypercellular (Type B) mucinous carcinomas, solid papillary carcinomas, invasive carcinomas of no special type with neuroendocrine features and ductal carcinomas in situ of neuroendocrine subtype were included in our study. The immunohistochemical panel included chromogranin A, synaptophysin, CD56, syntaxin-1 and INSM1. The specificity of syntaxin-1 and INSM1 was determined using samples negative for chromogranin A, synaptophysin and CD56. Results: The sensitivity of syntaxin-1 was 84.7% (50/59), with diffuse positivity in more than 60% of the cases. Syntaxin-1 also had an excellent specificity (98.1%). Depending on the definition for positivity, the sensitivity of INSM1 was 89.8% (53/59) or 86.4% (51/59), its specificity being 57.4% or 88.9%. The sensitivities of chromogranin A, synaptophysin and CD56 were 98.3, 74.6 and 22.4%, respectively. Discussion: Syntaxin-1 and INSM1 are sensitive and specific markers of breast tumors with neuroendocrine features, outperforming chromogranin A and CD56. We recommend syntaxin-1 and INSM1 to be included in the routine neuroendocrine immunohistochemical panel.

The panel of syntaxin 1 and insulinoma-associated protein 1 outperforms classic neuroendocrine markers in pulmonary neuroendocrine neoplasms.

Syntaxin-1 (STX1) is a recently described highly sensitive and specific neuroendocrine marker. We evaluated the applicability of STX1 as an immunohistochemical marker in pulmonary neuroendocrine neoplasms (NENs). We compared STX1 with established neuroendocrine markers, including insulinoma-associated protein 1 (INSM1). Typical carcinoids (n = 33), atypical carcinoids (n = 7), small cell lung carcinomas ([SCLCs] n = 30), and large cell neuroendocrine lung carcinomas (n = 17) were immunostained using tissue microarray for STX1, chromogranin A, synaptophysin, CD56, and INSM1. Eighty-four of eighty-seven (96.5%) NENs showed STX1 positivity. Carcinoids and LCNECs typically presented a combined strong membranous and weak cytoplasmic staining pattern; cytoplasmic expression was predominately observed in SCLCs. The sensitivity of STX1 was 90% in SCLCs and 100% in typical carcinoids, atypical carcinoids, and large cell neuroendocrine lung carcinomas. The overall sensitivity of STX1 in pulmonary NENs was 96.6%, and the sensitivity of the other markers was as follows: chromogranin A (85.2%), synaptophysin (85.2%), CD56 (92.9%), and INSM1 (97.7%). STX1 was found to be an excellent neuroendocrine marker of pulmonary NENs, with sensitivity and specificity surpassing that of classic markers. We propose a panel of STX1 and INSM1 for the routine immunohistochemical workup of pulmonary NENs.

Rare primary extranodal lymphomas: diffuse large B-cell lymphomas of the genital tract.

Primary non-Hodgkin's lymphoma (NHL) of the genital tract is a rare entity. Etiology and pathogenesis of these NHLs are unknown, although there might be a possible association between chronic inflammation and lymphomas. The most common histological subtype is the diffuse large B-cell lymphoma. We report two cases of uterine lymphoma and one case of prostate lymphoma in this paper. The symptoms and the differential diagnosis are also discussed. Because of the low incidence, there is no widely accepted consensus on its treatment. We demonstrate that the rituximab and CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone; R-CHOP) chemoimmunotherapy is a good and tolerable treatment option in all cases. The two young patients are disease-free nowadays; the older patient with poor prognostic histological-type lymphoma relapsed in a short time and died after second relapse. A multicenter analysis is necessary to evaluate the long-term results of chemoimmunotherapy in these rare extranodal lymphoma entities.

[Refractory sprue--precursor lesion of enteropathy type T-cell lymphoma--a clinicopathological case report]. / Refrakter sprue mint az enteropathia típusú T-sejtes lymphoma prekurzor laesiója--klinikopatológiai esetismertetés.

INTRODUCTION: Refractory sprue is characterised by distinctive morphologic alterations and the emergence of clonal intraepithelial lymphocytes. AIM: In this case report the authors emphasize the importance of histopathology in the diagnosis of refractory sprue. METHODS: The sequential biopsies from this patient have been investigated with routine histology, immunohistochemistry and molecular genetics for T-cell clonality analysis. RESULTS: The severely cachectic patient presenting with malabsorption syndrome has been diagnosed with celiac disease through a duodenal biopsy, and the CD8 negativity of the intraepithelial lymphocytes suggested the possible diagnosis of refractory sprue. Azathioprine and glucocorticoid therapy was administered due to the failed jejunal feeding and gluten-free diet, resulting in clinically complete, morphologically partial remission. Intestinal T-cell lymphoma developed in the ileocecal region within two years after the first clinical presentation. DISCUSSION: Refractory sprue and the enteropathy-type T-cell lymphoma constitute a disease spectrum. The reported case shows how a simple method can provide crucial information in the diagnosis of refractory sprue.

[Long-term survival after nasal NK/T cell lymphoma]. / Nazális NK/T-sejtes lymphoma hosszú túlélése.

The nasal NK/T cell lymphoma is a rare, extranodal non-Hodgkin lymphoma in western civilizations, which has poor prognosis. The Epstein-Barr virus can be detected in tumor cells in nearly all cases. There are no definite treatment guidelines in our days. There is no significant difference in survival between radiotherapy and chemotherapy according to Asian studies. In this case study we show our diagnostic procedures, our treatment options and we present the summary of this illness based on the data found in the literature.

[Primary T-cell lymphoma of the small bowel]. / Primer vékonybél T-sejtes lymphoma operált esete.

Primary malignancies in the small intestine are relatively rare. There are no specific methods to find these tumours in early stage. The authors report a case of a primary T-cell lymphoma in the small bowel that caused diagnostic challenges. A 66-year-old woman presenting with abdominal pain and and a palpable mass in the left upper quadrant of her abdomen was admitted into the hospital. Blood tests, endoscopic examinations, ultrasonography and CT scan could not reveal a definitive diagnosis. While a small bowel follow through examination demonstrated an entero-enteral fistula, its exact position could not have been determined. Consequently, an exploratory laparotomy was carried out, and a tumour was found involving the small bowel loops. The involved portion of the small intestine (with the fistula) was resected, and a side-to-side small bowel anastomosis was performed. Histological and immunohistochemical analyses revealed a primary T-cell lymphoma of the small bowel. There was no evidence of metastatic disease at the time of surgery. The patient received adjuvant chemotherapy, but three months later multiple lung metastases were detected. Small bowel malignant tumours cause significant diagnostic difficulties. Therefore, diagnosis and adequate treatment are usually delayed for some weeks. In the future, capsule endoscopy could help in the diagnostic work-up. Nevertheless, surgical exploration and resection of the tumour will be necessary for the correct diagnosis and treatment.

Mitotic Index Determined by Phosphohistone H3 Immunohistochemistry for Precise Grading in Follicular Lymphoma.

The World Health Organization classification recommends follicular lymphoma (FL) grading (G1-3) by considering centroblast number, while also suggesting its influence on disease outcome. As centroblast counting and other proliferation markers have limitations, we looked for more specific measures of cellular activity in FL. Phosphorylated histone H3 (pHH3) was widely applied for the objective detection of mitotic activity in different tumors. The aim was to evaluate the utility of pHH3 protein in FL grading and compare its value with the classical features of cell proliferation. Representative samples from 48 FL patients and 9 samples with follicular hyperplasia were examined. Hematoxylin-eosin-based mitosis index (HE-MI), number of mitotic figures based on anti-pHH3 immunohistochemical staining (pHH3-MI), and percentage of Ki-67-positive cells [proliferation index (PI)] were determined and compared with centroblast-based histologic grade. PHH3-MI showed significant correlation with HE-MI (r=0.85, P<0.0001) and PI (r=0.84, P<0.0001). All 3 cell proliferation parameters showed significant correlation with histologic grade: HE-MI versus grade, r=0.85 (P<0.0001); PI versus grade, r=0.74 (P<0.0001); pHH3-MI versus grade, r=0.80 (P<0.0001). PHH3-MI showed continuous increase with the histologic grade. The pHH3-MI value was distinctive between the G2 and the G1 FL groups (P<0.0001) and was increased in G3 FL compared with that in the G2 FL group (P=0.0020). In conclusion, easy-to-perform mitotic counting following phosphohistone H3 immunohistochemistry (pHH3-MI) correlates well with centroblast-based grading. PHH3 immunohistochemistry offers a reliable quantification tool supporting lymphoma grading and can be recommended as an additional parameter for the precise subcategorization of FL cases.