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Similar clinical features in follicular lymphomas with and without breaks in the BCL2 locus


Approximately 15% of follicular lymphomas (FLs) lack breaks in the BCL2 locus. The aim of this study was to better define molecular and clinical features of BCL2-breakpoint/t(14;18)-negative FLs. We studied the presence of BCL2, BCL6 and MYC breaks by fluorescence in situ hybridization and the expression of BCL2, MUM1, CD10, P53 and Ki67 in large clinical trial cohorts of 540 advanced-stage FL cases and 116 early-stage disease FL patients treated with chemotherapy regimens and radiation, respectively. A total of 86% and 53% of advanced- and early-stage FLs were BCL2-breakpoint-positive, respectively. BCL2 was expressed in almost all FLs with BCL2 break and also in 86% and 69% of BCL2-breakpoint-negative advanced- and early-stage FLs, respectively. CD10 expression was significantly reduced in BCL2-breakpoint-negative FLs of all stages and MUM1 and Ki67 expression were significantly increased in BCL2-break-negative early-stage FLs. Patient characteristics did not differ between FLs with and without BCL2 breaks and neither did survival times in advanced-stage FLs. These results suggest that the molecular profile differs to some extent between FLs with and without BCL2 breaks and support the notion that FLs with and without BCL2 breaks belong to the same lymphoma entity.


Follicular lymphoma (FL) is the most common indolent nodal B-cell lymphoma and derives from germinal center (GC) cells.1 Because of highly effective treatment regimens,2 the median overall survival (OS) of FL patients now reaches >10 years. Nevertheless, FL is still regarded an incurable lymphoma, as most of the patients develop resistance to therapy or more aggressive disease.3 The translocation t(14;18)(q32;q21) that leads to constitutive BCL2 expression in FL is detectable by fluorescence in situ hybridization (FISH) analysis in 85–90% of cases3, 4 and is thought to represent an early recurrent genetic event in FL and thus to be crucial for FL pathogenesis.5, 6, 7, 8 However, approximately 15% of FL grades 1–3A lack breaks in the BCL2 locus, indicative of the absence of t(14;18), and in only one-third of translocation-negative tumors BCL2 expression was reported.4, 9 Previous studies aimed at better defining t(14;18)-negative FL grades 1–3A with respect to their molecular profile.4, 10, 11 These studies revealed that t(14;18)-negative FL express the GC B-cell markers BCL6 and IRF8 in all and CD10 in 70% of cases, show ongoing somatic hypermutation and aberrant somatic hypermutation and express activation-induced cytidine deaminase at comparable levels to t(14;18)-positive FL. Moreover, gains of the REL gene locus were detected in approximately one-third of t(14;18)-negative FL, while common features of marginal zone lymphomas were absent.4 Nevertheless, former investigations also showed that there are subtle but significant differences with regard to gene expression and miRNA profiles between FL with and without t(14;18). For example, an enrichment of late GC B-cell signatures, nuclear factor-κB and proliferation signatures and a significant downregulation of miR16 expression were observed in t(14;18)-negative FL.4, 11 In line with these results, CD10 expression was significantly downregulated, the Ki67 proliferation rate was higher and the expression of IRF4/MUM1as well as the expression of the miR16 targets CHEK1 and CDK6 were significantly upregulated in a validation cohort of t(14;18)-negative FL by immunohistochemistry.4, 11 However, very little information so far is available concerning a possible clinical difference between FL with and without t(14;18). Moreover, no information is available about the frequency and the molecular impact of t(14;18) in early-stage FL. Our study, therefore, explored the frequency of t(14;18) in advanced- and early-stage FL in two large clinical trial cohorts of the German Low Grade Lymphoma Study Group (GLSG) with the aim to identify potential biological and clinical differences between FL with and without t(14;18).

Materials and methods

FL specimens

The current study included 540 and 116 advanced- and early-stage FL patients, respectively. All patients had been classified as FL grades 1–3A according to the guidelines of the world health organization (WHO) classification of lymphoid neoplasms (WHO 2008),1 and the diagnosis was confirmed by one of the six German reference centers of lymph node pathology. Advanced FL patients in clinical stages III/IV had been recruited to the GLSG 1996 trials, comparing MCP (melphalan, chlorambucil and prednisone) with CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone), and to the GLSG 2000 trial, comparing CHOP with CHOP and rituximab (R-CHOP).12, 13, 14 Advanced-stage FL patients that met the clinical entry criteria were all 18 years, were untreated and were all in need of therapy.

Early-stage FL patients were newly diagnosed, age >18 years, recruited in 2000–2006, presented with only nodal manifestations and were part of a study that compared different radiotherapy regimens.15 This early-stage FL study set includes 11 defined cases of limited stage III disease with low tumor load and restricted manifestation pattern.

Clinical information of 518 advanced-stage FL patients was available (407 with t(14;18)-status). Twenty-eight patients were treated with MCP, 232 patients with CHOP and 258 with R-CHOP. Limited clinical characteristics were available for 108 early-stage FL patients. Patients’ characteristics of the current study cohorts are given in Table 1. The studies were approved by the responsible ethics committees.

Table 1 Patient characteristics of advanced- and early-stage FLs

Detection of chromosomal breakpoints in BCL2, BCL6 and MYC genes

The presence or absence of chromosomal breaks in BCL2, BCL6 and MYC was investigated by FISH in a tissue microarray format as described previously,16, 17 using BCL2, BCL6 and MYC break-apart probes (Abbott Molecular, Ludwigshafen, Germany). Each case was evaluated by at least two independent observers using Zeiss microscopes (Zeiss, Oberkochen, Germany). Given that non-IGH translocation partners are very rare in FL, FL with a break detected in BCL2 are also referred to as 't(14;18)-positive FL'.


The BCL2, CD10, IRF4/MUM1, Ki67, BCL6 and P53 expression status was determined in a tissue microarray format according to standard protocols.

All cases with FL stages III/IV were stained for BCL2 (Clone 124, DAKO, Glostrup, Denmark, 1:400, Clone 100-D5, EMERGO, Hague, The Netherlands, 1:25, Clone E17, 1:100, Cell Marque, Rocklin, CA, USA), CD10 (NCL-CD10 270, Novocastra, Newcastle upon Tyne, UK, 1:100), Ki67 (MIB-1, DAKO, 1:800), IRF4/MUM1 (MUM-1p, DAKO, 1:800), BCL6 (Clone pG/B6p, DAKO, 1:20) and P53 (Clone DO-7, DAKO, 1:50), while cases with FL stages I/II were stained for BCL2, CD10, Ki67, IRF4/MUM1 and BCL6. The markers BCL2, Ki67 and BCL6 were evaluated in quartiles. P53 and MUM1 were evaluated in 10% steps. A case was assigned to be BCL2-, CD10- or BCL6-positive when >25% of FL cells expressed the respective protein. Cut points for MUM1 (10%) and Ki67 (25%) were chosen according to our previous publication.4 FL expressing P53 in at least 30% of tumor cells were referred to as P53-positive.

Statistical evaluation

The correlation between the presence or absence of t(14;18) and (i) the occurrence of a chromosomal break in BCL6 or MYC, (ii) the expression of BCL2, CD10, Ki67, IRF4/MUM1 or P53 and (iii) clinical patient characteristics, overall response and complete remission rates were assessed by Fisher’s exact tests followed by Bonferroni–Holm adjustment. Moreover, Fisher’s exact test was used to assess the correlation between t(14;18) status with (i) the incidence of grade 3A FL, (ii) the occurrence of a diffuse growth pattern and (iii) the initial treatment regimen (MCP, CHOP, R-CHOP). Clinical outcome variables were OS from diagnosis to death from any cause, censored at last contact in patients alive and time to treatment failure (TTF) from the start of therapy to stable disease at end of induction, progression or death from any cause, censored at the latest tumor assessment in patients alive without treatment failure. Differences in OS and TTF between advanced-stage FL with and without t(14;18) and difference in survival between FL grades 1–2 and FL grade 3A and FL with and without a diffuse growth pattern were assessed by a Kaplan–Meier approach using the Log-rank test for significance.


The majority of advanced- and early-stage FL are grade 1–2 and show a follicular growth pattern

The information on histological grade was available in 533 out of 540 advanced-stage FL and in 105 out of 116 early-stage FL. Out of 533 advanced-stage FL, only 12 (~2%) FL showed a blast count consistent with FL grade 3A while all early-stage FL were diagnosed as FL grades 1–2. A diffuse growth pattern was evident in 8 out of 410 (~2%) advanced-stage FL and in 3 out of 83 (~4%) early-stage FL with available information on the growth pattern.

t(14;18) is absent in approximately 15% of advanced-stage FL and 50% of early-stage FL

Out of the 540 advanced-stage FL and 116 early-stage FL, we successfully evaluated the BCL2-breakpoint status by FISH in 422 (78%) and 107 (92%) cases, respectively. The remaining cases were excluded from analysis owing to technical failure or poor tissue quality.

In line with the current knowledge,3, 4 we detected chromosomal breaks in BCL2 in 86% of the advanced-stage FL (363/422; Figure 1). Somewhat unexpected, however, only ~53% of early-stage FL (57/107) carried a BCL2 break. This finding points to a clear enrichment of t(14;18)-negative cases in early-stage FL and may suggest alternative molecular mechanisms of FL pathogenesis in those cases or at least a different initiating event.

Figure 1

Assessment of the BCL2-breakpoint/t(14;18) status and BCL2 expression status. The BCL2-breakpoint status was assessed by FISH and the BCL2 expression status by immunohistochemistry (IHC) in two clinical trial cohorts of the GLSG with advanced-stage FL (FL III/IV) (n=540) and early-stage FL (FL I/II(III)) (n=116). BAP=break-apart probe.

With regard to histological grade in advanced-stage FL, there was a correlation between the absence of t(14;18) and the occurrence of FL grade 3A (4/56 (~7%) vs 5/361 (~1%), P=0.022). However, there was no enrichment of FL with a diffuse growth pattern in FL with or without t(14;18) (3/282 vs 2/46 in advanced-stage FL, P=0.15 and 2/46 vs 1/32, P>0.99 in early-stage FL). Finally, the percentage of t(14;18)-positive patients was not different with respect to the initial treatment regimen (MCP: 79%, CHOP: 84%, R-CHOP: 89%, P=0.17).

The majority of t(14;18)-negative FL express BCL2

t(14;18) juxtaposes the BCL2 gene next to the IGH enhancer locus, which leads to a constitutive expression of BCL2 protein in FL cells. Indeed, by immunohistochemistry we found that almost all early- and advanced-stage FL that carry a t(14;18) express BCL2 (99% in advanced-stage FL (clone 124: 95.5% vs E17: 96% vs 100-D5: 96% and 100% in early-stage FL (clone 124: 97%, E17: 97%, 100-D5: 100%), Figure 1), in line with previous findings.18, 19, 20 However, in contrast to published data,4, 9, 19, 20 we detected BCL2 expression also in the majority of t(14;18)-negative FL (86% in advanced-stage FL (clone 124: 60% vs E17: 72% vs 100-D5: 77%) and 69% in early-stage FL (clone 124: 53%, E17: 72%, 100-D5: 67%, Figure 1). This indicates that mechanisms other than t(14;18) lead to BCL2 expression in most t(14;18)-negative FL. BCL2 expression levels (weaker than or comparable to bystander T-cells) did not differ between FL with or without t(14;18) (data not shown).

BCL6 and MYC breaks are not significantly enriched in t(14;18)-negative FL

Translocations of BCL6 and MYC have been reported in FL and are usually enriched in FL Grade 3B, blastoid FL or transformed FL, as shown for MYC-alterations, or in CD10 and BCL2-negative FL Grade 1–3A, as shown for BCL6 translocations.21, 22, 23, 24, 25 In this study, we did not observe a significant enrichment of BCL6 breaks in FL with or without t(14;18) (11% vs 16% in advanced-stage FL (P=0.26) and 12% vs 10% in early-stage FL (P>0.99), Figure 2)4 nor did we observe an enrichment of MYC breaks in one of the subgroups (2% vs 2% in advanced-stage (P>0.99) and 7.5% vs 5% in early-stage FL (P=0.67)). We only observed an enrichment of BCL6-breakpoint-positive cases in the cohort of BCL2-protein-negative advanced-stage FL, as shown previously (data not shown).24 This enrichment was, however, not observed in early-stage FL. Chromosomal MYC breaks were observed in 9 of 382 (2.4%) and in 5 of 80 (6.3%) successfully evaluated advanced- and early-stage FL, respectively. Of note, all of these cases were FL grade 1/2 and showed no sign of transformation. All 9 advanced-stage FL were affected by a double hit (8/9 MYC+BCL2, 1/9 MYC+BCL6). However, the presence of a MYC break in FL patients with a BCL2 break was not associated with TTF (P=0.61). In the cohort of early-stage FL, two cases were only affected by a MYC break, two cases were affected by a MYC and a BCL2 break and one showed a triple hit. Interestingly, the frequency of MYC breaks detected in the tumor cells of early-stage FL was much lower than the frequency of BCL2 breaks within the same cases (<25% MYC-breakpoint-positive cells in 4/5 cases vs >50% BCL2-breakpoint-positive cells in 3/3 cases with BCL2 and MYC breaks), while the frequency of MYC-, BCL2- or BCL6 breaks did not differ in advanced-stage FL (all >50%). Notably, the early-stage FL with a triple hit was the only FL with >50% MYC-breakpoint-positive cells.

Figure 2

Correlation of t(14;18) status with the breakpoint status of BCL6 and MYC. Chromosomal breaks in BCL2, BCL6 and MYC were assessed by FISH in two clinical trial cohorts of the GLSG with advanced-stage FL (n=540) and early-stage FL (n=116). t(14;18) status did not significantly correlate with the occurrence of BCL6 and/or MYC breaks in advanced-stage FL (FL III/IV) and early-stage FL (FL I/II(III)).

CD10 expression is significantly reduced in t(14;18)-negative FL

We detected an expression of CD10 in >90% of t(14;18)-positive and BCL2-positive FL of all stages (Figure 3), however, in only 68% of t(14;18)-negative advanced-stage FL, in line with previous findings (P<0.001).1, 4, 24 Moreover, CD10 expression was absent in even 45% of t(14;18)-negative early-stage FL (P<0.001). Vice versa, CD10-negative FL were significantly enriched in FL lacking t(14;18). Specifically, 37% of CD10-negative advanced-stage FL stages and 80% of CD10-negative early-stage FL were found to be t(14;18)-negative, whereas only 9% of CD10-positive advanced-stage FL and 34% of CD10-positive early-stage FL were t(14;18)-negative (P<0.001). Moreover, an association between the lack of CD10 expression and the presence or absence of BCL2 expression was observed in advanced-stage FL (P=0.016, not significant after Bonferoni adjustment) while no association was observed in early-stage FL (data not shown).

Figure 3

(a and b) Correlation of t(14;18) status with the expression status of BCL2, CD10, MUM1/IRF4 and P53 and the Ki67 proliferation rate in advanced-stage FL (a) and early-stage FL (b). The breakpoint status of BCL2 was assessed by FISH and correlated with the expression status of BCL2, CD10, MUM1/IRF4 and P53 and the proliferation status was assessed by Ki67 immunohistochemistry (IHC) in two clinical trial cohorts of the GLSG with advanced-stage FL (n=540) and early-stage FL (n=116). BCL2 and CD10 expression was significantly reduced in t(14;18)-negative advanced-stage FL (FL III/IV) and early-stage FL (FL I/II(III)), after Bonferroni–Holm adjustment. P53 expression and in early-stage FL also the MUM1 expression and the Ki67 proliferation status were enriched in t(14;18)-negative FL, however, not significantly after Bonferroni–Holm adjustment.

Expression of P53 and IRF4/MUM1 and Ki67 proliferation status in t(14;18)-negative FL

As we previously observed an enrichment of the proliferation and post-GC B-cell signatures in t(14;18)-negative FL,4 we also investigated the expression of IRF4/MUM1, Ki67 and P53 in the two clinical study cohorts of the GLSG. We observed an enrichment of cases that stained positive for P53 and a slight increase of MUM1 expression in t(14;18)-negative advanced-stage FL (P=0.03, P=0.22). In early-stage, FL P53 expression was also increased (P=0.07) and MUM1 and Ki67 were significantly higher expressed in t(14;18)-negative FL as compared with t(14;18)-positive FL (P=0.01, P=0.05) (Figure 3).

t(14;18)-negative and t(14;18)-positive advanced- and early-stage FL show no difference in major clinical features

To address the question whether t(14;18)-negative FL differ from their t(14;18)-positive counterparts in clinical behavior, we correlated the t(14;18) status of advanced-stage FL and early-stage FL with patient characteristics such as FLIPI (Follicular Lymphoma International Prognostic Index) and lactate dehydrogenase status (Tables 2A and 3). There was no relevant difference between t(14;18)-negative and t(14;18)-positive FL of all stages with regard to patient characteristics (Tables 2A and 3).

Table 2 (A and B) Correlation of t(14;18) status with patient characteristics (A) and response to chemotherapy (B) in advanced-stage FL
Table 3 Correlation of t(14;18) status with patient characteristics in early-stage FL

t(14;18)-negative and t(14;18)-positive advanced-stage FL show no difference in survival

A comparison between FL patients with and without BCL2 break/t(14;18) did not reveal any difference in length of survival times. Specifically, we neither observed a significant difference in OS (P=0.116, Figure 4a) nor in TTF (P=0.466, Figure 4b). Similar results were observed after adjustment for type of initial therapy (adjusted P=0.17 and P=0.69). Interestingly, however, a tendency toward an inferior overall response to initial therapy (P=0.015) but not with regard to complete remission (P=0.50) was observed in t(14;18)-negative FL stages III/IV (Table 2B). Moreover, histological grade (FL 1–2 vs FL 3A) and growth pattern (follicular vs diffuse) did neither correlate with OS (P=0.77 and P=0.42) nor with TTF (P=0.68 and P=0.56). Overall, these results suggest that t(14;18)-negative advanced-stage FL do show a similar clinical behavior when compared with their t(14;18)-positive counterparts.

Figure 4

Correlation of t(14;18) status with survival in advanced-stage FL. (a) Time to treatment failure (TTF) and (b) OS in t(14;18)-positive (n=351) and t(14;18)-negative (n=56) advanced-stage FL by Kaplan–Meier using the Log-rank test for significance. FL with and without t(14;18) show a similar TTF and OS. x axis: years, y axis: survival rate.


t(14;18) that leads to constitutive BCL2 expression is thought to be an initiating and crucial event in FL pathogenesis.1, 5, 6, 7, 8 To address the question which genetic event may substitute for the presence of t(14;18) and the subsequent expression of BCL2 in ~15% of t(14;18)-negative FL grades 1–3A patients, we and others have investigated this FL subgroup in more detail.4, 10, 11 However, these previous studies were performed in a rather small patient cohort comprised of samples from Northern America and Europe diagnosed between 1974 and 2001 and treated with a wide range of therapies.4, 26 Here, we were aiming to confirm and extend our molecular and clinical findings in larger and more uniform study cohorts derived from prospective randomized clinical trials. To this end, we analyzed the BCL2-, BCL6- and MYC-breakpoint status as well as the BCL2, CD10, Ki67, IRF4/MUM1 and P53 expression status in two large clinical trial study cohorts of the GLSG.12, 13, 27 By FISH analysis, we found that 86% of advanced-stage FL were affected by chromosomal breaks in BCL2, in line with previous findings (Figure 1).3, 4 However, BCL2 breakage indicating both t(14;18) as well as other non-IGH translocations were detected in only 53% of early-stage FL, which is a new and surprising finding. Of note, early-stage FL in this clinical study cohort did neither include the subgroup of predominantly diffuse t(14;18)-negative FL described by our group that are localized to the inguinal region nor other FL that are characterized by the absence of t(14;18), for example, primary cutaneous FL.28, 29 Thus it seems that the majority of patients who present with early-stage/localized FL, irrespective of the phenotype or the localization, develop FL via a molecular strategy that is different from an underlying t(14;18).

In the early-stage FL cohort, the parameters of clinical course, including risk of relapse in correlation to t(14;18) status, will be addressed in a separate report.

Interestingly, most of t(14;18)-negative FL of both cohorts strongly expressed BCL2, which is also a new and unexpected finding as compared with previous results4, 9, 19, 20 (Figure 3). We are unable to provide a clear explanation for this discrepancy; however, improved immunohistochemical detection techniques over the past years may account, at least in part, for this finding. Notably, chromosomal gains of BCL2 that were described in a former study9 and that might account for a t(14;18)-independent BCL2 expression were encountered in only a small number of cases and were observed in FL with and without t(14;18) with a slight enrichment in t(14;18)-positive FL (data not shown). Moreover, a high frequency of BCL2 expression was also evident using each of the three BCL2 antibodies that all recognize different epitopes (clone 124, E17, 100-D5). The overall BCL2 expression rate increased slightly, however, when the antibodies were used in combination (data not shown). Unexpectedly, the BCL2 clone E17, that was described to be specifically useful for the detection of translocated and mutated BCL2,18, 30 was not superior to the clone 100-D5 in t(14;18)-positive FL in the present study cohorts and the clone 124 from DAKO-stained BCL2 at similar frequencies as compared with the clone E17 (advanced-stage FL (clone 124: 94%, E17: 93%, 100-D5: 95%) early-stage FL (clone 124: 77%, E17: 85%, 100-D5: 88%)).

Overall, these results suggest that expression of BCL2 can not only be induced by t(14;18) but also by several other—as yet unknown—genetic or regulatory events and that constant BCL2 expression—independent of the presence of t(14;18)—may be an important pathogenetic event in the majority of FL cases. Thus future investigations will need to focus on the detection of genetic or other regulatory events that may drive BCL2 expression and on the identification of a genetic or molecular hit that may substitute for both t(14;18) and BCL2 expression in the minority of t(14;18)-negative FL that lack BCL2 expression. Similar to the setting of ‘precursor cells’ in t(14;18)-positive FL, one may postulate that t(14;18)-negative ‘precursor cells’ also exist in t(14;18)-negative FL, which carry (as yet) undetected molecular alteration(s) leading, for example, to upregulation of the BCL2 protein.

Besides the detection of BCL2 translocations and BCL2 protein expression, we also investigated the occurrence of BCL6 and MYC breaks and the expression status of the GC marker CD10, the post-GC marker IRF4/MUM1, the proliferation marker Ki67 and P53 in FL with and without t(14;18). We detected MYC breaks in a small but not negligible subset of advanced-stage FL (2%) and early-stage FL (~6%), which is a rare finding in FL grades 1/2.22, 25 However, in line with our previous observations, we did not observe a significant enrichment of BCL6 breaks in FL with or without t(14;18)4 nor did we observe a significant enrichment of MYC breaks in one of the subgroups (Figure 2).

Nevertheless, it might be worth mentioning that MYC breaks were only present in a small number of tumor cells in early-stage FL as compared with the corresponding BCL2 and BCL6 breaks of the same cases, whereas advanced-stage FL harbored cells with MYC breaks in comparable numbers as compared with BCL2 breaks that were present in >50% of scored nuclei (major clone) in ~93% of advanced-stage FL stages and 87% of early-stage FL (results not shown). This observation may lead to the hypothesis that MYC translocations are present in only minor subclones in early-stage FL, where they could drive tumor progression and subsequently become detectable in major subclones of advanced-stage FL or transformed FL. Of note, the only early-stage FL that showed MYC translocations in >50% of tumor cells was the singular case with a triple-hit constellation (breaks in the loci of MYC, BCL2 and BCL6). Interestingly, the occurrence of a double hit in advanced-stage FL of this study cohort did not correlate with a worse clinical outcome.

The immunohistochemical analysis detected only a slight increase in IRF4/MUM1 expression and a slight but significant increase of P53 expression in advanced-stage FL without t(14;18). Moreover, we observed a significant increase of IRF4/MUM1 expression and a significant higher Ki67 proliferation rate in t(14;18)-negative FL as compared with t(14;18)-positive FL in early-stage FL (Figure 3). A distinctly significant difference was a prominent reduction in CD10 expression in t(14;18)-negative FL, as previously observed4 that was especially prominent in early-stage FL, which is a new finding of the current study. Thus our results still support our previous hypothesis that t(14;18)-negative FL have features of a late GC phenotype of B-cell differentiation but belong to the molecular spectrum of classical FL.4, 10, 11 Only minor differences between t(14;18)-negative and t(14;18)-positive advanced- and early-stage FL were observed with regard to clinical parameters that included patient characteristics such as FLIPI, lactate dehydrogenase and hemoglobin risk. Specifically, we observed no significant difference in TTF and OS between advanced-stage FL with and without t(14;18) (Figures 4a and b).

In summary, we could not detect relevant clinical differences in tumors with and without t(14;18) in advanced-stage FL, providing further evidence that both FL subgroups belong to the same lymphoma entity. The absence of t(14;18) in almost 50% of early-stage FL but concomitant expression of BCL2 in the majority of t(14;18)-negative FL, however, suggests that the expression of BCL2—independent of t(14;18)—constitutes an important adjunct to the pathogenesis in these FL tumors as well. The answer to the question, as to whether the clinical course of t(14;18)-negative FL is similar to that of t(14;18)-positive FL also in localized early-stage FL will be part of our future investigations.


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GO, HH and AS were supported by the Robert-Bosch-Stiftung (Stuttgart, Germany) and the German José Carreras Leukemia Foundation (München, Germany) grant DJCLS R 10/28. We thank all members of the German Low Grade Lymphoma Study Group (GLSG) who are not co-authors of this study as well as Theodora Nedeva, Heike Brückner, Eva Bachmann, Olivera Batic and Claudia Becher and Reina Zühlke-Jenisch for technical assistance.

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Correspondence to A Rosenwald.

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Leich, E., Hoster, E., Wartenberg, M. et al. Similar clinical features in follicular lymphomas with and without breaks in the BCL2 locus. Leukemia 30, 854–860 (2016).

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