BL is an aggressive B-cell lymphoma with a variable incidence in different geographic regions of the world. According to Rabkin et al,25
in endemic areas (Equatorial Africa), the incidence rate varies between 5 and 10 per 100,000 children younger than 15 years, while in the United States this value is closer to 2 per million. In Brazil, the epidemiologic status of BL remains to be elucidated.17
Previous studies on BL in this country have been predominantly from the Northeast,15,16
with an emphasis on the pediatric population. This is the first large-scale study of BL in Brazil, including pediatric and adult populations, and also the first to analyze cases from the Central West and North regions. Brazil is a remarkably diverse country. The South and Southeast regions are more developed socioeconomically and have greater percentages of European descendants. The North includes the Amazon rain forest and is endemic for malaria and other tropical and infectious diseases.20
It should be emphasized, however, that the cases of BL studied herein were received as consultation cases. So, a bias in the number of cases from different regions could influence the low number of cases from the North region. In further studies, we intend to refine the characterization of BL in the North region of Brazil where malaria is a public health problem.
In our study of BL, there was a male predominance (male/female ratio, 2.8:1), and pediatric cases (n = 143) outnumbered adult cases (n = 88). We also observed a higher frequency of extranodal (159 cases) than nodal (67 cases) involvement. In the cases with extranodal involvement, intra-abdominal organs were affected in 129 (81.1%) of 159 cases, while in only 5 cases (3.1%) was jaw/maxilla the initial site. This is clearly distinct from the typical mandibular presentation found in Africa.2,8,12
Lymph node involvement was more common among the adult than the pediatric population, in concordance with the literature.26
Therefore, in this extensive analysis of BL from Brazil, the clinical features were similar to the sporadic form of BL seen in the United States and Europe.2,26,27
Only in the Central West and South regions did the adult group outnumber the pediatric group.
It is well established that there is a significant association of BL with EBV with a variable frequency, depending on the clinicopathologic variant. EBV is present in the majority of endemic cases of BL (up to 100%) and in only 15% to 30% of sporadic cases from the United States.2,12,28
In Brazil, there are few studies that have analyzed the frequency of association of EBV in BL. Araujo et al15
and Sandlund et al16
studied this association in the Northeast region of Brazil in a pediatric population and reported that 87% (47 of 54 cases) and 73% (8 of 11 cases), respectively, were EBV+. In our study, in this geographic region, we observed a lower frequency of association between EBV and BL (63%; 54 EBV+ cases of 86 BL cases evaluated), although this included adult and pediatric cases. In the Southeast region, Gutierrez et al,13
Bacchi et al,14
Klumb et al,17
and Hassan et al18,29
obtained different frequencies of association between BL and EBV, varying from 58% to 72%. In this particular region, we observed that half of the cases of BL were EBV+ (36/72 cases). The South region had the lowest frequency of association (29%), a result that is similar to sporadic BL in developed countries.2,28
However, in a previous study in this same region, Haralambieva et al19
reported that 50% of their BL cases were EBV+. In the Central West region, 47% of the cases were EBV+. The highest frequency of association was observed in the North, in which 76% of the cases of BL were EBV+. This establishes the existence of a substantial group of classical, non-AIDS associated BL cases in Brazil that occurs at a frequency that is much higher than that of EBV−, sporadic BL cases as observed in the United States and Europe.
Our study on BL showed a total of 123 EBV+ cases (by ISH) in the overall population (52.6%) and, as previously demonstrated in Brazil,15,17
the EBV+ group (mean age, 16 years) was younger than the EBV− group (mean age, 23 years). These results, and those of previous studies,2,12
demonstrate that Brazil as a country has an intermediate association of BL with EBV, although this association is much more pronounced in the more tropical regions. Among adult cases of BL in our series, there was a notably higher percentage of EBV+ tumors than has been reported among sporadic variants of the tumor in the United States and Europe.30
Therefore, the pathogenesis of adult cases of BL in Brazil and other equatorial countries may differ from that seen in wealthier nations. This also may have important therapeutic implications, given that antiviral nucleosides may have activity in EBV-associated lymphomas.31,32
EBV strains can be categorized into 2 types (A and B), and a geographic prevalence of these strains has been observed.15
Analysis of the coding region of the EBNA
2 gene in endemic BL has revealed a high prevalence of both EBV types. Type B EBV is also identified at high frequency in healthy people in Equatorial Africa,33
while type A EBV is almost exclusively found in the peripheral blood of people from developed Western countries34
and is more frequently found in sporadic BL.35
It is also known that patients with AIDS have an increased prevalence of infection with type B EBV.35,36
By studying the EBNA
2 gene, we determined that 95 (77.2%) of the EBV+ BLs contained type A EBV and 24 (19.5%) contained type B EBV, a pattern intermediate between that observed in endemic BL33
and North American cases.35
The South region of Brazil showed the lowest percentage of EBV type B (only 8%), a result similar to sporadic BL in the United States.35
In contrast, the Central West region showed the highest percentage of EBV type B (50%; 4 cases), a pattern similar to that found in endemic BL.33
The distribution of EBV strains in the Northeast and Southeast regions () revealed similar results to previous reports in these same geographic regions.15,17,18,29
Among our 14 HIV+ BLs, 10 were EBV+ (by ISH) and only 2 cases (20%) were EBV type B, in contrast with results reported in the literature.35,36
A relationship between immunodeficiency and neoplasia had been recognized for longer than a decade before the emergence of the AIDS epidemic.37
HIV infection is associated with a high incidence of NHL (100–400 times higher than among the general population), Kaposi sarcoma, anal human papillomavirus, and cervical carcinoma. The 2 most common types of this NHL are diffuse large B-cell lymphoma and BL,9
the latter being the first NHL to be described in association with HIV infection and corresponding to about 30% of NHLs in HIV+ patients.8
Our HIV-associated BL showed a male/ female ratio of 3.6:1. Among the 14 HIV+ BL cases, 12 were adults with only 2 pediatric cases, and nodal involvement at diagnosis was more frequent than extranodal involvement. Studies38,39
have demonstrated that the frequency of EBV association in HIV-associated BL varies from 25% to 50%. In 1996, we studied 24 AIDS-related lymphoma cases in Brazil40
; 5 were BLs and all were in adults. Only 2 cases (40%) were EBV+. In this study, we observed a greater association between EBV and HIV-associated BL (71%; 10 cases) as compared with the findings of previous studies38–40
but similar to the frequency reported by Lazzi et al41
in Africa, who demonstrated 6 EBV+ cases (75%) among 8 HIV-associated BLs.
Most EBV+ BL cases (whether endemic, sporadic, or AIDS-associated) typically display more restricted forms of latency, usually latency type I, only expressing EBER1 and EBER2 and EBNA1,11,12
and, as we and others showed, at least the EBV BART microRNAs.42
LMP-1 is not typically expressed in BL. In our study, only 1 case of BL was positive for LMP-1 protein by immunohistochemical analysis in a few cells. Similar results have also been described in the literature; Niedobitek et al43
observed expression of LMP-1 protein in a variable proportion of tumor cells in 2 cases of endemic BL. In Brazil, Araujo et al15
and Chen et al34
reported LMP-1 expression in 2 cases and 1 case of BL, respectively. At this point, the significance of this observation with regard to clinical prognosis, outcome, or molecular mechanism remains to be elucidated.
(also called p53
) is a key tumor suppressor gene that is mutated or lost in approximately 50% of all human cancer cases worldwide, including hematologic malignancies. It is activated in response to a variety of cellular and genotoxic stress conditions, leading to the induction of growth arrest, apoptosis, DNA repair, senescence, and differentiation.44
It has been reported that 30% of endemic BL tumors and up to 70% of long-established BL lines carry mutations in p53
Bhatia et al45
mutations in 37% of cases of BL from Argentina and Brazil and concluded that the presence of mutated p53
in BL is independent of the geographic origin of the tumor, the 8;14 chromosomal breakpoint locations, and EBV association. Studies have shown that in some high-grade NHLs, the occurrence of positive immunostaining does not reflect point mutations in the p53
gene and vice versa.46
Villuendas et al47
found overexpression of p53 protein in 5 (63%) of 8 BL cases, and Klumb et al48
reported p53 overexpression in 13 (46%) of 28 pediatric BL cases, although the mutation was demonstrated, by PCR, in only 7 of these 13 cases. In our study, p53 protein expression was observed in 38 cases (16.2%), fewer than in previous studies. This lower percentage can be explained, in part, by the cutoff of 10% used herein, while previous studies used a cutoff of 5%.47,48
More important, we studied a far greater number than any of the prior studies, which we believe yields a more accurate representation of p53 expression in BL (at least in Brazil).
We have sequenced primary pediatric BL cases obtained from the Northeast region of Brazil. The first 13 cases analyzed were wild-type by sequence (data not shown). We also noted a trend toward p53 overexpression in EBER1 ISH-negative BLs. Therefore, the association between mutant p53
and BL may be less than originally thought, and other mechanisms, such as EBV viral genes or epigenetic modifications, may inactivate the p53 pathway. Alternatively, the p53 pathway may be evaded by MYC
mutations, as has been demonstrated in a BL animal model.49
p63 is a transcription factor that contains multiple isoforms with various biologic activities.50
gene locus at chromosome 3q28 bears significant homology to the tumor suppressor gene p53
and to the related gene p73.
-related genes, encode various isoforms with transactivation, DNA binding, and tetramerization domains.51
p63 protein exhibits a consistent expression pattern in normal tissues such as squamous epithelia, urothelium, basal cells of prostatic and breast glands, and reticular epithelium of the normal thymus and also in a subset of lymphocytes in the germinal center of morphologically normal lymph nodes.52,53
Among hematolymphoid neoplasms, p63 expression has been reported in blast crisis in chronic myelogenous leukemia,54
follicular lymphoma, diffuse large B-cell lymphoma,51
isolated cases of chronic lymphocytic leukemia, marginal cell lymphoma,52
and in 44% of anaplastic large cell lymphoma.55
There are few articles reporting the expression of p63 in lymphoid malignancies, and, to the best of our knowledge, this is the first study to evaluate its expression in a large number of BL cases. We observed that only 9 (3.8%) of the 234 BL cases expressed p63 protein, and coexpression of protein p53 and p63 was observed in only 1 case.
In this study of the largest number of cases from Latin America analyzed to date, we have demonstrated that BL in Brazil is diverse and regionally distinct. EBV association is sporadic, and, perhaps, HIV-associated BL is higher than seen in the United States and Europe. Overexpression of p53 was infrequently observed, and dysfunction of this critical tumor suppressor in BL may be linked to other factors rather than inactivating mutations. Prospective studies of BL in patients undergoing standardized chemotherapy regimens are now underway.
Upon completion of this activity you will be able to:
- define the 3 major types of Burkitt lymphoma and their patterns of incidence and organ involvement.
- describe the range of association with Epstein-Barr virus and tumor suppressor protein expression (p53 and p63) in various Burkitt lymphoma subtypes.
- describe the range of clinicopathologic characteristics of Burkitt lymphoma in Brazil.
- recognize that there may be geographic and regional differences in the patterns and types of Burkitt lymphoma and define an approach with which diagnostic pathologists may investigate and characterize the features of Burkitt lymphoma in their own practice locales.
- comment on whether immunochemical staining for LMP-1 and p63 is indicated in Burkitt lymphoma.
The ASCP is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The ASCP designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit ™ per article.
The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose.