- Top of page
- Materials and Methods
- Disclosure statement
Follicular lymphoma (FL) frequently transforms into diffuse large B-cell lymphoma (DLBCL). To clarify the associated clinicopathological prognostic parameters, we examined the correlation of 11 histopathological parameters with progression-free survival (PFS) and overall survival (OS) in 107 consecutive patients who had DLBCL with pre-existing (asynchronous) or synchronous FL. The patients comprised 58 men and 49 women with a median age of 56 years. For DLBCL, the complete response rate was 81%, overall response rate was 88%, and 5-year PFS and OS rates were 55% and 79%, respectively. Immunohistochemical analysis of the DLBCL component revealed the following positivity rates: CD10, 64%; Bcl-2, 83%; Bcl-6, 88%; MUM1, 42%; GCB, 82%; cMyc index ≥80%, 17%; and Ki-67 index ≥90%, 19%. IGH/BCL2 fusion was positive in 57% of DLBCL cases. In univariate analyses, asynchronous FL and DLBCL (24%, P = 0.021), 100% proportion of DLBCL (29%, P = 0.004), Bcl-2 positivity (P = 0.04), and high Ki-67 index (P = 0.003) were significantly correlated with shorter PFS. Asynchronous FL and DLBCL (P = 0.003), 100% proportion of DLBCL (P = 0.001), and high Ki-67 index (P = 0.004) were significantly correlated with shorter OS. In a multivariate analysis, asynchronous FL and DLBCL (P = 0.035) and 100% proportion of DLBCL (P = 0.016) were significantly correlated with shorter OS. Thus, asynchronism and 100% proportion of DLBCL, that is, FL relapsed as pure DLBCL, or FL and DLBCL at different sites, were significant predictors of unfavorable outcome of patients with DLBCL transformed from FL.
Follicular lymphoma (FL) is one of the most common subtypes of non-Hodgkin lymphoma in the Western world, accounting for 22% of all cases worldwide. The risk of FL transformation was reported to be approximately 20% at 8 years.[2, 3] Transformation to diffuse large B-cell lymphoma (DLBCL) is observed frequently, with cells most commonly resembling centroblasts, but occasionally resembling anaplastic large cells with CD30 expression. In rare cases, transformation to Burkitt or Burkitt-like lymphoma or precursor B-lymphoblastic lymphoma/acute lymphoid leukemia has been noted. Composite FL and Hodgkin lymphoma have been suggested to represent two morphologic manifestations of the same tumor clones.[8, 9]
Transformation to DLBCL is frequently associated with a rapidly progressive clinical course and death from a tumor that is refractory to treatment. Ghesquières et al. analyzed 60 DLBCLs transformed from low-grade B-cell lymphoma and reported that complete remission with multidrug chemotherapy regimens was achieved in 60% of the patients, but 48% of them relapsed. Overall survival (OS) and freedom-from-progression rates at 5 years were 57% and 33%, respectively.
In recent years, several analyses of genetic alterations that appear to affect the risk for FL transformation have been reported, including activation of cMYC,[6, 11] inactivation of TP53,[12, 13] and inactivation of p16INK4a.[14, 15] However, few histopathological and immunohistochemical analyses of transformed FL have been performed.[12, 16, 17] Hans et al. reported that FL grade 3 cases with a predominant diffuse component (>50% diffuse) had a significantly worse overall survival and event-free survival than the remaining FL grade 3 cases.
Since 2000, DLBCL has been subdivided into germinal center B-cell (GCB) and non-GCB subgroups (including the activated B-cell phenotype [ABC] and type 3 phenotype) by using the cDNA microarray technique.[18, 19] The GCB subgroup shows a better outcome and includes cases with a translocation (14;18)(q32;q21). In clinical practice, Hans et al. showed that a panel of immunohistochemical markers comprising CD10, Bcl-6, and MUM1 could be used on paraffin-embedded tissues to classify DLBCL as tumors with a GCB or non-GCB phenotype. Davies et al. examined 35 cases of transformed FL and found that 89% of them had a GCB phenotype and 9% had a non-GCB phenotype. We previously reported that 84% of transformed FL cases had a GCB phenotype and 16% had a non-GCB phenotype. However, the prognostic implications were not determined.
The translocation (14;18)(q32;q21) is present in 80–100% of FLs in Western countries,[21, 22] whereas in South-east Asia, including Japan, the incidence of translocation has been reported to be considerably lower at approximately 60%. The outcome of the patients with DLBCL transformed from FL with t(14;18) is unclear, although we recently reported that this fusion does not affect clinical outcome.
The aim of this study is to clarify the histopathological prognostic parameters of DLBCL transformed from FL. Eleven histopathological parameters influencing progression-free survival (PFS) and/or OS were evaluated using univariate and multivariate analyses, including the presence of synchronous/asynchronous FL and DLBCL, the proportion of DLBCL, the highest grade of FL, expressions of CD10, Bcl-2, Bcl-6, MUM1, cMyc, and Ki-67, classification as GCB/non-GCB subgroups, and detection of IGH/BCL2 fusion using fluorescence in situ hybridization (FISH) analysis.
- Top of page
- Materials and Methods
- Disclosure statement
Follicular lymphoma transforms primarily to DLBCL followed by intermediate DLBCL/Burkitt lymphoma, classical Hodgkin lymphoma, and B acute lymphoblastic leukemia. Transformation of FL to DLBCL is currently the focus of widespread clinical and pathological interest. We therefore studied the histopathological prognostic parameters of DLBCL transformed from FL using morphological, immunohistochemical, and FISH analyses.
To evaluate the outcome of patients with DLBCL transformed from low-grade B-cell lymphoma, Ghesquières et al. analyzed 60 such cases, and reported that OS and freedom-from-progression rates at 5 years were 57% and 33%, respectively. The better outcomes for patients in our present study (5-year PFS rate, 55% and 5-year OS rate, 79%) might be partly associated with the younger median age (56 years) and relative frequency of cases with a low/low-intermediate International Prognostic Index. In addition, most of these patients received rituximab-containing treatment, although the benefit of rituximab was not proved in the current study.
Multivariate analysis revealed that asynchronism and 100% proportion of DLBCL were significantly correlated with shorter OS. In addition, a high number of regimens administered (≥3) prior to transformation to DLBCL was correlated with a poor outcome. Our results suggested that patients with asynchronous FL and DLBCL, that is, patients who received prior chemotherapy regimens before the diagnosis of DLBCL, might have developed chemoresistance before receiving treatment for DLBCL. Among patients with DLBCL transformed from FL, the proportion of large lymphoid tumor cells ranged from 16 cells/high-power field to 100%. The present study suggested that a high proportion of large tumor cells as 100% was a poor prognostic parameter. As a result, subgroup analysis according to the presence of synchronous and asynchronous FL and DLBCL, and the proportion of DLBCL cells revealed that asynchronous FL and DLBCL and a 100% proportion of DLBCL cells (FL relapsed as pure DLBCL or FL and DLBCL at different sites) had a significantly worse outcome than the remaining three groups. In contrast, the remaining three groups had a tendency of better outcome, suggesting that initially treated patients with synchronous FL and DLBCL and those with asynchronous FL and DLBCL in whom FL relapsed as mixed FL and DLBCL (histologically “transforming” FL) showed better PFS and OS.
The Ki-67 index is associated with the proliferation activity of tumors. A high Ki-67 index is reported to be a poor prognostic parameter in de novo DLBCL; however, the issue is controversial. In the present study, Ki-67 was a significant predictor of PFS and OS in univariate analyses, although this significance was not sustained in multivariate analysis. We found that a 100% proportion of DLBCL in DLBCL transformed from FL displayed a worse outcome than the other groups. In addition, our results suggested that transformation to pure DLBCL with a high Ki-67 index was a poor prognostic indicator for transformed FL.
The Bcl-2 protein, an anti-apoptotic molecule, is expressed on resting B and T cells, but not on normal germinal center cells. Bcl-2 positivity has been reported to be associated with unfavorable prognosis in de novo DLBCL.[26, 28, 29] In the present study, Bcl-2 positivity predicted significantly shorter PFS in cases of DLBCL transformed from FL, and patients negative for Bcl-2 showed 100% 5-year OS. Conversely, patients with a low FL grade who were positive for IGH/BCL2 fusion tended to have poorer PFS and OS, although these results were not significant. We found that 57% of the cases had IGH/BCL2 fusion in DLBCL transformed from FL, and this frequency was similar to that reported for Japanese FL cases. Because Bcl-2 positivity, low grade of FL, and IGH/BCL2 fusion positivity were usually correlated with each other, they might be markers indicating a poor prognosis for cases of DLBCL transformed from FL.
In the present study, CD10, Bcl-6, and MUM1 were expressed in 64%, 88%, and 42% of the cases of DLBCL transformed from FL, and 82% were of GCB phenotype, whereas 18% were of non-GCB phenotype. Several previous studies examining difference in prognosis between de novo DLBCL patients with GCB phenotype and those with non-GCB phenotype revealed that the former group had a more favorable prognosis.[30, 31] However, this has recently become a controversial issue.[26, 32] In the present study, neither GCB versus non-GCB nor the expression of CD10, Bcl-6, or MUM1 was a significant prognostic factor for cases of DLBCL transformed from FL.
In conclusion, asynchronism and 100% proportion of DLBCL, that is, FL relapsed as pure DLBCL or FL and DLBCL at different sites, were predictors of shorter PFS and OS in patients with DLBCL transformed from FL.