Fbw7 Inhibits the Progression of Activated B-Cell Like Diffuse Large B-Cell Lymphoma by Targeting the Positive Feedback Loop of the LDHA/lactate/miR-223 Axis.

Background: F-box and WD repeat domain-containing 7 (Fbw7) is well known as a tumor suppressor and ubiquitin ligase which targets a variety of oncogenic proteins for proteolysis. We previously reported that Fbw7 promotes apoptosis in diffuse large B-cell lymphoma (DLBCL) through Fbw7-mediated ubiquitination of Stat3. This study aimed to identify the mechanism of Fbw7-mediated aerobic glycolysis reprogramming in DLBCL. Methods: Expression levels of Fbw7 and Lactate Dehydrogenase A (LDHA) in human DLBCL samples were evaluated by immunohistochemistry. Crosstalk between Fbw7 and LDHA signaling was analyzed by co-immunoprecipitation, ubiquitination assay, western blotting and mRNA quanlitative analyses. In vitro and in vivo experiments were used to assess the effect of the Fbw7-mediated LDHA/lactate/miR-223 axis on DLBCL cells growth. Results: Fbw7 could interact with LDHA to trigger its ubiquitination and degradation. Inversely, lactate negatively regulated Fbw7 via trigging the expression of miR-223, which targeted Fbw7 3'-UTR to inhibit its expression. In vivo and in vitro experiments revealed that miR-223 promoted tumor growth and that the effects of miR-223 on tumor growth were primarily related to the inhibition of Fbw7-mediated LDHA's ubiquitination. Conclusions: We demonstrated that the ubiquitin-ligase Fbw7 played a key role in LDHA-related aerobic glycolysis reprogramming in DLBCL. Our study uncovers a negative functional loop consisting of a Fbw7-mediated LDHA/lactate/miR-223 axis, which may support the future ABC-DLBCL therapy by targeting LDHA-related inhibition.

Consistency Analysis of Programmed Death-Ligand 1 Expression between Primary and Metastatic Non-Small Cell Lung Cancer: A Retrospective Study.

Background: Programmed death-ligand 1 (PD-L1) expression in non-small cell lung cancer (NSCLC) is considered as a predictive biomarker of anti-PD-1/PD-L1 cancer therapies. However, the correlation of PD-L1 expression status between the primary and paired metastatic NSCLC is still not clear. The current study aims to address this specific issue. Materials and Methods: The PD-L1 expression of the primary and paired metastatic lesions from 110 patients with NSCLC was retrospectively evaluated by immunohistochemical assay using Anti-PD-L1 antibody, Clone 22C3. The results were assessed by the Tumor Proportion Score (TPS) using cutoff values of <1%, 1%-49% and ≥50%. Meanwhile, the Cohen's kappa coefficient (k) of agreement was calculated. Results: An overall concordance rate of the PD-L1 expression between the primary and metastatic lesions was 61% (63/103) (k = 0.39, and P < 0.001). If using TPS considering 1% and 50% as a threshold, the inconsistent rate was 28/103 (27.2%) paired specimens (k = 0.46, and P < 0.001) and 14/103 (13.6%) paired specimens (k = 0.53, and P < 0.001), respectively. Moreover, the concordance of the PD-L1 expression between primary and metastatic tumor was also analyzed according to the clinical stages within the untreated group of patients. We observed that for patients with stage I-III NSCLC, the concordance rate of the PD-L1 expression between primary and metastatic lesions was 81.3% and 100% when using 1% and 50% as threshold, respectively. While in stage IV patients, the concordance rate of the PD-L1 expression between the primary and metastatic lesions drops to 71.4% and 85.7%, respectively. Conclusion: The PD-L1 expression was dynamic as tumor developed, which was valuable in selecting the proper type of sample for accurately evaluating the prognosis of using pembrolizumab as first or second line treatment.

Impact of the updated 2018 ASCO/CAP guidelines on HER2 FISH testing in invasive breast cancer: a retrospective study of HER2 fish results of 2233 cases.

OBJECTIVES: Human epidermal growth factor receptor 2 (HER2, ERBB2) is a valuable prognostic and predictive biomarker in breast cancer. Accurate assessment of HER2 status is essential in selecting the patients with invasive breast cancer who will likely response to HER2-targeted therapies. Some major modifications in the diagnostic recommendation for fluorescence in situ hybridization (FISH) have been made in the updated 2018 American Society of Clinical Oncology (ASCO)/College of American Pathologist (CAP) guideline. According to the revised guideline, concomitant IHC assays are required to arrive at the most accurate HER2 status designation after HER2 FISH equivocal results; however, little is known about its influence on the clinical practice of pathologist. The purpose of this study was to evaluate the impact of the revised 2018 ASCO/CAP guidelines on the HER2 status designation. METHODS: We retrospectively reviewed the HER2 FISH testing results from 2233 cases of invasive breast cancer between January 2014 and December 2017. Concomitant immunohistochemistry (IHC) were performed on the same tissue blocks that were used for the FISH testing. RESULTS: Compared to the 2013 guidelines, the HER2 status in 183 (8.2%) cases were re-defined when reassessed by the 2018 guidelines. Among these 183 cases, 175 equivocal cases according to the 2013 guideline were re-defined as HER2 negative (n = 173) or HER2 positive (n = 2). Eight previously classified as HER2 positive cases were converted to negative in the 2018 scheme, all of which were with HER2 IHC scores of 1+ or 2+. The number of cases in the negative category was 1705 according to the 2018 guidelines as opposed to 1524 by the 2013 guidelines. CONCLUSIONS: The updated 2018 ASCO/CAP guidelines eliminated the FISH equivocal category, which can be attributed to reflex HER2 IHC, and partly ease the dilemma for clinical practice. Reflex IHC for FISH equivocal cases is of prime importance; furthermore, HER2 FISH results were converted from positivity to negativity based on the concomitant IHC results in a small percentage of cases. In all, implementation of the 2018 ASCO/CAP guidelines provides much clearer instructions and recommendations for the HER2 status designation, and thus reduces the risk of misdiagnosis.

Correction: MYC Expression in Concert With BCL2 and BCL6 Expression Predicts Outcome in Chinese Patients With Diffuse Large B-Cell Lymphoma, Not Otherwise Specified.

[This corrects the article DOI: 10.1371/journal.pone.0104068.].

Impact of repeat HER2 testing after initial equivocal HER2 FISH results using 2013 ASCO/CAP guidelines.

PURPOSE: The updated 2013 American Society of Clinical Oncology/College of American Pathologists guideline recommendations for human epidermal growth factor receptor 2 (HER2) testing have made some major changes in HER2 fluorescence in situ hybridization (FISH) interpretation criteria with additional FISH equivocal cases. Repeat HER2 testing is recommended after initial HER2 FISH equivocal results; however, little is known about its impact on final HER2 status. The aim of this study is to investigate whether reflex test clarifies HER2 status, and to characterize clinicopathological features of the newly defined HER2 equivocal group. METHODS: A total of 886 consecutive cases of primary invasive breast cancer conducted with dual-probe HER2 FISH testing between November 2013 and December 2015 were reviewed. HER2 immunohistochemistry (IHC) and FISH testing were performed on a different tissue block or a new specimen after initial HER2 FISH equivocal results. RESULTS: Compared to 2007 guideline, 85 (9.6%) cases changed their category by using 2013 guideline. The major change of the 85 cases is that 57 (6.4%) cases in HER2 FISH-negative category changed to equivocal, and the equivocal category cases increased from 36 to 67. HER2 FISH equivocal was significantly associated with HER2 IHC equivocal (2+) and chromosome 17 polysomy (P < 0.01). Repeat testing by IHC and FISH clarified HER2 status in 33 and 42% of HER2 equivocal cases, respectively. Overall 32 (48%) initial HER2 equivocal cases stayed HER2 equivocal after repeat FISH and or IHC testing. These tumors were ER/PR+, with high KI-67 index. CONCLUSION: New guidelines classify more HER2 FISH equivocal cases. Repeat HER2 testing clarifies HER2 status in about 50% of initial HER2 FISH equivocal cases. In addition, HER2 equivocal cases merit further study as there is limited information about prognosis and optimal treatment strategy for this population.

Diffuse large B cell lymphoma associated with chronic inflammation arising within atrial myxoma: aggressive histological features but indolent clinical behaviour.

AIMS: Primary cardiac lymphoma (PCL) is a rare neoplasm. PCL is fatal, unless it is diagnosed and treated early. Recently, a small number of cases of diffuse large B cell lymphoma (DLBCL) arising within atrial myxoma have been reported in immunocompetent patients and showed aggressive histological features but an indolent clinical behaviour. METHODS AND RESULTS: We present four unusual cases of Epstein-Barr virus (EBV)-positive DLBCL arising within atrial myxoma with detailed clinical, histological, immunophenotypical and genotypical features in immunocompetent patients, and review the literature for 11 similar cases. All the patients appeared to have morphological features of DLBCL, B lineage immunophenotype, high proliferative index and latency type III of EBV infection. They achieved complete tumour resection without chemotherapy or radiotherapy after surgery and were healthy at 3- and 7-month and 7- and 10-year follow-ups, respectively. CONCLUSIONS: We suggest that this lymphoma should be regarded as a unique DLBCL associated with chronic inflammation (DLBCL-CI) because of an indolent clinical behaviour to avoid excessive or unnecessary treatments. In addition, early accurate diagnosis and complete resection of this tumour are crucial for optimal patient outcome.

Myxoid Adrenocortical Adenoma: A report of two cases and literature review.

Myxoid adrenocortical adenomas are uncommon. There were only 61 cases reports documented, and the tumors are tended to be misdiagnosed in virtue of being rare and distinctive histological features. Recently we encountered two myxoid adrenocortical adenoma cases of a 31-year-old Chinese woman and a 45-year-old Chinese man. The patients did not receive further treatment after surgery and were still alive after following up for 20 months. Myxoid adrenocortical adenomas is extremely rare. Recognition of this entity would be beneficial for pathologists to avoid msidiagnosis, and unnecessary treatment.

Fbw7 regulates apoptosis in activated B-cell like diffuse large B-cell lymphoma by targeting Stat3 for ubiquitylation and degradation.

BACKGROUND: The ubiquitin-ligase Fbw7 acts as a tumor suppressor, targeting lots of proto-oncogenes for proteolysis. However, the exact role of Fbw7 in diffuse large B-cell lymphoma (DLBCL) development remains unclear. METHODS: We evaluated Fbw7 expression in patient samples of DLBCL using immunohistochemical staining. The effect of Fbw7 overexpression on cell viability and apoptosis was investigated using activated B-cell (ABC) like DLBCL cell lines. The mechanism of Fbw7 activity in DLBCL was investigated using immunoprecipitation, ubiquitination, western blot and qualitative analyses. RESULTS: The non-germinal center B-cell-like subtype of DLBCL showed reduced Fbw7 expression compared with the germinal center B-cell (GBC) subtype, and low Fbw7 expression was associated with a worse prognosis. Fbw7 overexpression caused decreased cell viability and increased apoptosis rates in the ABC-DLBCL cell lines SU-DHL-2 and OCI-LY-3. Importantly, Stat3 and phospho-Stat3Tyr705 stability were reduced following Fbw7 overexpression in ABC-DLBCL cell lines. In HEK293T and SU-DHL-2 cells, we demonstrated that Fbw7 interacts with Stat3 and pStat3Tyr705 to regulate their ubiquitylation and degradation. Downstream anti-apoptotic target genes of activated Stat3, including Myc, Survivin, Mcl-1, Pim-1, Bcl-2 and Bcl-xl showed decreased mRNA expression following exogenous Fbw7 overexpression. The negative relationship between Fbw7 and pStat3Tyr705 levels was also confirmed in DLBCL patient samples. CONCLUSION: The ubiquitin-ligase Fbw7 mediates apoptosis through targeting Stat3 for ubiquitylation and degradation in ABC-DLBCL. Thus, our study may offer a promising approach for ABC-DLBCL therapy through Stat3 inhibition.

Intravascular NK/T-cell lymphoma: a series of four cases.

Intravascular natural killer/T-cell lymphoma (IVNKTL) is a rare disorder and is reported gradually increased recently. We presented four cases including two extremely rare cases of primary lung IVNKTL with detailed clinicopathological features, therapy and prognosis, and reviewed the literature for 25 similar cases. H&E, Immunohistochemical staining and in situ hybridization (ISH) were used in the study. The medium-sized lymphoid cells were characterized by the selective growth within the kumina of vessels, particularly capillaries. The endothelial cells in the vessels exhibited positive CD34 staining. The lymphoid cells were positive for NK/T-cell markers, and cytotoxic proteins, and negative for B-cell markers. ISH demonstrated that the lymphoid cells expressed EBER. All the patients died of the disease a few months later. To conclude, the overall survival of patients with IVNKTL is very poor and the 1-year survival rate is only 31%. Patients with B symptoms and multiple organs involvement may be associated with the poor clinical prognosis. We deduce that the traditional chemotherapy with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) is inadequate for the treatment of IVNKTL. Early accurate diagnosis by biopsy for this lymphoma may be crucial for the patients' medical prognosis due to the fatal disease course.

Overexpression of SRC-3 promotes esophageal squamous cell carcinoma aggressiveness by enhancing cell growth and invasiveness.

Steroid receptor coactivator-3 (SRC-3), a transcriptional coactivator for nuclear receptors and other transcription factors, plays an important role in the genesis and progression of several cancers. However, studies investigated the role of SRC-3 in esophageal squamous cell carcinomas (ESCCs) are limited, and the role of SRC-3 in tumor progression remains unclear. We examined the expression of SRC-3 in 8 ESCC cell lines and 302 human ESCC tissues by qPCR, Western blot, and immunohistochemistry. In addition, ESCC cell lines were subjected to proliferation and invasion assays, tumorigenicity assay, flow cytometry assay, qPCR, Western blot, and Chromatin Immunoprecipitation assay to investigate the role of SRC-3 in cancer progression. SRC-3 was overexpressed in 48% of cases and correlated with poor overall (P = 0.0076) and progression-free (P = 0.0069) survival of surgically resected ESCC patient. Cox regression analysis revealed that SRC-3 is an independent prognostic marker. Furthermore, we found that activation of insulin-like growth factor (IGF)/AKT) was involved in the SRC-3 on the cell growth and invasiveness in two ESCC cell lines, Eca109 and EC18 cells. SRC-3 overexpression is clinically and functionally relevant to the progression of human ESCC, and might be a useful molecular target for ESCC prognosis and treatment.

[Expression and significance of HGAL and LMO2 in follicular lymphoma].

OBJECTIVE: To evaluate the diagnostic value of HGAL and LMO2 expression and compare with CD10 and bcl-6 in follicular lymphoma (FL). METHODS: 63 cases of FL were collected from Guangdong General Hospital. The expression of HGAL, LMO2, CD10 and bcl-6 was assessed by immunohistochemistry. RESULTS: The expression rates of HGAL, LMO2, CD10 and bcl-6 were 98.4% (62/63), 82.5% (52/63), 82.5% (52/63) and 87.3% (55/63), respectively. The expression rate of HGAL was higher than those of LMO2, CD10 and bcl-6, but the differences were not significant (P>0.05). There was no significant difference in HGAL, LMO2 and bcl-6 expression among FL1, FL2 and FL3 cases. The CD10 expression rate of FL1-3A cases was significantly higher than that of FL3B cases(P<0.01). CONCLUSIONS: HGAL and LMO2, especially HGAL, can be used in FL particularly high grade FL as useful germinal center marker.

PIK3R1 targeting by miR-21 suppresses tumor cell migration and invasion by reducing PI3K/AKT signaling and reversing EMT, and predicts clinical outcome of breast cancer.

We have previously shown that dysregulation of miR-21 functioned as an oncomiR in breast cancer. The aim of the present study was to elucidate the mechanisms by which miR-21 regulate breast tumor migration and invasion. We applied pathway analysis on genome microarray data and target-predicting algorithms for miR-21 target screening, and used luciferase reporting assay to confirm the direct target. Thereafter, we investigated the function of the target gene phosphoinositide-3-kinase, regulatory subunit 1 (α) (PIK3R1), and detected PIK3R1 coding protein (p85α) by immunohistochemistry and miR-21 by RT-qPCR on 320 archival paraffin-embedded tissues of breast cancer to evaluate the correlation of their expression with prognosis. First, we found that PIK3R1 suppressed growth, invasiveness, and metastatic properties of breast cancer cells. Next, we identified the PIK3R1 as a direct target of miR-21 and showed that it was negatively regulated by miR-21. Furthermore, we demonstrated that p85α overexpression phenocopied the suppression effects of antimiR-21 on breast cancer cell growth, migration and invasion, indicating its tumor suppressor role in breast cancer. On the contrary, PIK3R1 knockdown abrogated antimiR­21-induced effect on breast cancer cells. Notably, antimiR-21 induction increased p85α, accompanied by decreased p-AKT level. Besides, antimiR-21/PIK3R1-induced suppression of invasiveness in breast cancer cells was mediated by reversing epithelial-mesenchymal transition (EMT). p85α downregulation was found in 25 (7.8%) of the 320 breast cancer patients, and was associated with inferior 5-year disease-free survival (DFS) and overall survival (OS). Taken together, we provide novel evidence that miR-21 knockdown suppresses cell growth, migration and invasion partly by inhibiting PI3K/AKT activation via direct targeting PIK3R1 and reversing EMT in breast cancer. p85α downregulation defined a specific subgroup of breast cancer with shorter 5-year DFS and OS, which may require more aggressive treatment.

[Clinicopathologic analysis of HIV-negative plasmablastic lymphoma].

OBJECTIVE: To study the clinical, pathologic, immunophenotype, molecular characteristics and prognosis of HIV-negative plasmablastic lymphoma (PBL). METHODS: Twelve cases of HIV-negative PBLs diagnosed between 2005 and 2014 in Guangdong General Hospital were identified according to WHO classification of tumors of haematopoietic and lymphoid tissues (2008). The clinicopathologic features and outcome were analyzed and the relevant literatures were reviewed. RESULTS: The patients were predominantly male (11/12) with a median age of 55.5 years. The tumor cells showed the characteristic combination of immunoblastic/plasmablastic morphology, plasma cell phenotype and high proliferation, no expression of mature B cell markers. 7/10 of the cases were EBER positive. Two cases were positive for C-myc translocation. Four of twelve patients were died. CONCLUSIONS: PBL is a rare, aggressive B-cell lymphoma. HIV-negative PBL has lower rate of oral involvement and EBER expression than HIV-positive patients, the differential diagnosis is very challenging, and the prognosis is worse.

Intravascular large B-cell lymphoma involving gastrointestinal stromal tumor: a case report and literature review.

BACKGROUND: Intravascular large B-cell lymphoma is a rare and aggressive lymphoma with a dismal prognosis. Synchronous intravascular large B-cell lymphoma involving gastrointestinal stromal tumor has not previously been documented. CASE PRESENTATION: We report a case of a 61-year-old Chinese woman who presented with high fever of unknown origin for 20 days, and hematemesis, melena for 2 days. A computed tomography scan revealed a mass lesion located in the anterior wall of the stomach. Surgery was performed to remove the tumor and histopathology showed a gastrointestinal stromal tumor and a synchronous intravascular large B-cell lymphoma. The patient refused further treatment and died 4 months after surgery. CONCLUSIONS: To the best of our knowledge, this case represents the first report of synchronous intravascular large B-cell lymphoma involving a gastrointestinal stromal tumor.

MYC expression in concert with BCL2 and BCL6 expression predicts outcome in Chinese patients with diffuse large B-cell lymphoma, not otherwise specified.

Recent studies provide convincing evidence that a combined immunohistochemical or fluorescence in situ hybridization (FISH) score of MYC, BCL2, BCL6 proteins and MYC translocations predicted outcome in diffuse large B-cell lymphoma (DLBCL) patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). However, by far, all these researches are based on Western populations. Therefore, we investigate the prognostic relevance of MYC-, BCL2- and BCL6-rearrangements and protein expression by immunohistochemistry and FISH from 336 de novo DLBCL, NOS treated with CHOP or R-CHOP. Breaks in MYC and BCL6, and fusion in IGH/BCL2 were detected in 9.7%, 20.0%, and 11.1% of the cases, respectively, and were not significantly associated with clinical outcomes. Protein overexpression of MYC (≥40%), BCL2 (≥70%) and BCL6 (≥50%) was encountered in 51%, 51% and 36% of the tumors, respectively. On the basis of MYC, BCL2 and BCL6 expression, double-hit scores (DHSs) and triple-hit score (THS) were assigned to all patients with DLBCL. Patients with high MYC/BCL2 DHS, high MYC/BCL6 DHS and high THS had multiple adverse prognostic factors including high LDH level, poor performance status, advanced clinical stage, high International Prognostic Index (IPI) score, and non-germinal center B-cell. In univariate analysis, high MYC/BCL2 DHS, high MYC/BCL6 DHS and high THS were associated with inferior OS and PFS in both CHOP and R-CHOP cohorts (P<0.05). The highly significant correlations with OS and PFS were maintained in multivariate models that controlled for IPI (P<0.05). DLBCLs with high DHSs and high THS share the clinical features and poor prognosis of double-hit lymphoma (P>0.05). These data together suggest that the immunohistochemical DHSs and THS defined a large subset of DLBCLs with double-hit biology and was strongly associated with poor outcome in patients treated with R-CHOP or CHOP.

[B-cell lymphomas with concurrent myc and bcl-2/IgH or bcl-6 translocations].

OBJECTIVE: To identify and investigate clinicopathological features of B cell lymphomas with concurrent myc and bcl-2/IgH or bcl-6 translocations ("double-hit" lymphoma). METHODS: Tissue microarray was constructed from formalin-fixed and paraffin-embedded tissue samples of aggressive B cell lymphomas diagnosed between 2009 and 2012, including 129 cases of diffuse large B cell lymphoma (DLBCL), 5 cases of B-cell lymphoma, unclassifiable with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma (BCLU), 7 cases of Burkitt lymphoma and 4 cases of high-grade follicular lymphoma with diffuse large B cell lymphoma component. Interphase fluorescence in-situ hybridization (FISH) was performed with a panel of probes including myc, bcl-2/IgH and bcl-6 to document related gene translocation and copy number changes. Medical record review was performed and follow-up data was recorded. RESULTS: Among 145 cases, 5 cases (3.4%) of B cell lymphomas with concurrent myc and bcl-2/IgH or bcl-6 rearrangements (double-hit lymphomas) were identified, including 2 cases involving myc and bcl-2 translocations (1 DLBCL and 1 BCLU), and 3 cases involving myc and bcl-6 translocations (all DLBCLs). Three cases with concurrent bcl-2/IgH and bcl-6 translocations were found. Single gene translocations or increase of copy numbers were found in 66 cases, representing 51.2% (66/129) of all de novo DLBCLs. Ki-67 index of the 5 "double-hit" lymphomas ranged from 60% to 100%. Clinical follow-up data were available in 4 of the 5 "double-hit" lymphoma patients, three of whom died within 2 years and 1 patient was alive after 36 months of follow-up. CONCLUSIONS: "Double-hit" B-cell lymphomas are rare and can only be identified by molecular detection. They should not be considered synonymous with BCLU morphologically, and may present entities within other morphological spectra. Most of the patients have a poor prognosis. Further in-depth studies of larger case numbers are required to determine the pathologic and genetic variables of the lesion.

Immunophenotypic features and t(14;18) (q32;q21) translocation of Chinese follicular lymphomas helps to distinguish subgroups.

BACKGROUND: The revised 2008 World Health Organization classification maintains a histological grading system (grades 1-3) for follicular lymphoma (FL). The value of grading FL has been debated. This study will yield deeper insights into the morphologic, immunophenotypic characterization and t(14;18) translocation in FL and explore their significance of diagnosis of Chinese FL subgroups. METHODS: We retrospectively reviewed the FL diagnoses according to the 2008 WHO classification in all diagnostic specimens from a multicentric cohort of 122 Chinese patients. Upon review, 115 cases proved to be truly FL. CD10, BCL6, MUM1, BCL2 and t(14;18) (q32;q21) translocation were detected by Envision immunostaining technique and fluorescence in situ hybridization. RESULTS: FL1 has larger proportion of follicular pattern (93.0%) than that of FL2 (73.7%, P = 0.036), FL3B (63.6%, P = 0.003) and FL3A (77.4%, P = 0.053), although the last P value was more than 0.05 (Pearson's chi-squared test). Areas of DLBCL were present in 25.8% (8/31) of FL3A and more frequent in FL3B (59.1%, 13/22; P = 0.015). The positivity of CD10 and BCL2 in FL1-2 were significantly higher than those in FL3 (P < 0.001, P = 0.043, respectively). The positivity of MUM1 in FL1-2 was significantly lower than that in FL3 (10.2% vs. 51.0%; P < 0.001). Furthermore the positivity of MUM1 in FL3A was significantly lower than that in FL3B (37.9% vs. 68.2%; P = 0.032). The positivity of t(14;18) was higher in FL1-2 than in FL3 (73.5% vs. 35.6%, P < 0.001), and was higher in FL3A than in FL3B (51.9% vs. 11.1%, P = 0.005). t(14;18) was significantly correlated with CD10+ (R = 0.453, P < 0.001) and MUM1+ (R = -0.482, P < 0.001). CONCLUSIONS: FL1 and FL2 were immunophenotypically and genomically similar, while FL3A and FL3B were partly immunophenotypically similar but morphologically, genomically distinct. FL3A was genomically closer to FL1-2, whereas FL3A was genomically closer DLBCL. Thus we hypothesize that FL may in fact be a heterogeneous indolent lymphoma encompassing entities with distinct molecular pathogenesis and genetic characteristics. Immunohistochemical and genetic characterization helps to distinguish subgroups of FLs. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1334018129864616.