Case 4 -
B-cell Lymphoma, Unclassifiable, with Features Intermediate Between Diffuse Large B-cell Lymphoma and Burkitt Lymphoma
Steven H. Swerdlow
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88 year old woman who hit her head on the sink when she
bent to pick up a brush and developed a lump on her forehead. Initial CT was interpreted as a small left
frontal scalp hematoma. She had persistent shoulder/neck pain, went to the ER and her shoulder was
injected with steroids and she was given oral steroids as well. After some pain relief, the patient
presented again 4 weeks following her injury to the hospital with diplopia, a persistent "hematoma" and
severe neck pain. Following a repeat CT and an MR, an excisional biopsy was performed and is submitted
for your review. She developed pericardial tamponade and left sided cardiac failure unresponsive to
medical therapy, was found to have involvement of the liver and probably other sites and expired about
one week following her biopsy.
Case 4 - Slide 1
Case 4 - Figure 1
Note the diffuse proliferation associated with a "starry sky" related to the scattered tingible body macrophages.
Case 4 - Figure 2
This high magnification field looks very much like a Burkitt lymphoma with rather uniform intermediate sized transformed lymphocytes and scattered tingible body macrophages.
Case 4 - Figure 3
Note how some of the neoplastic cells have very clefted nuclei.
Case 4 - Figure 4
Here the neoplastic cells are even more pleomorphic and include a very large multinucleate cell.
Case 4 - Figure 5
The Wright-Giemsa stained cytospin shows intermediate to large sized transformed cells with sometimes vacuolated basophilic cytoplasm.
Case 4 - Figure 6 - CD3
There are relatively few scattered CD3+ cells.
The histologic sections demonstrated a diffuse
proliferation of intermediate to larger transformed lymphoid cells associated with a starry sky pattern
due to scattered tingible body macrophages. There were individually apoptotic cells as well as larger
areas of apoptosis. The transformed cells varied in size, some had very clefted nuclei and there were
even some very large multinucleate forms. The cells had variably vacuolated basophilic cytoplasm as seen
on a cytospin of the cell suspension used for the flow cytometric studies.
Flow cytometric immunophenotypic studies:
CD5-, CD10-, CD20+, kappa
monoclonal population with admixed heterogeneous T-cells.
Paraffin section immunohistochemical & in situ hybridization stains:
CD20+, CD10 some possible weak positivity, bcl-6+, bcl-2+, Ki-67 -- almost 100% positive, MUM-1+, ALK1-,
EBER ISH for EBV-, CD3 -- scattered positive small cells.
Cytogenetic FISH studies:
nuc ish 3q27(BCL6sp)/3q27(BCL6st, nuc
ish 8q24(MYCsp)/8q24(MYCst), nuc ish 14q32(IGHx2), 18q21(BCLx2). In other words, BCL6 and MYC rearranged but not BCL2.
B-cell lymphoma, unclassifiable, with features intermediate between diffuse large
B-cell lymphoma and Burkitt lymphoma (MYC and BCL6 rearranged) (aka, Diffuse large B-cell lymphoma with "high grade"
We will concentrate on the major differential diagnoses here which include the first three on the
list. Primary cutaneous diffuse large B-cell lymphoma, leg type must be considered because
clinically the mass would have been consistent with a deeply invasive cutaneous lymphoma. The pure
population of transformed B-cells and the phenotype (CD10-, bcl6+, MUM-1+, bcl-2+) are typical for this
entity (although not specific), MYC or BCL6
translocations have been reported to be present in a majority of cases, these lymphomas occur most
frequently in older females and they are not restricted to the leg.  However, the diagnosis
of a primary cutaneous lymphoma requires no evidence of extracutaneous disease at diagnosis (although
they can then disseminate afterward -- I didn't write the rules!). Blastoid (pleomorphic) mantle cell
lymphomas can resemble a lymphoblastic lymphoma or diffuse large B-cell lymphoma. The upcoming WHO
Bluebook will use the term blastoid for the mantle cell lymphomas that resemble lymphoblastic lymphomas
and pleomorphic for the more pleomorphic cases with larger cells and often prominent nucleoli that have
diffuse large B-cell in the differential. None of the features of the case being presented specifically
suggested such a diagnosis with the absence of CD5 expression, the strong expression of MUM-1 and
presence of both MYC and BCL6 translocations
(no individual feature is specific, however). If there was more concern for this possibility,
documenting a lack of cyclin D1 and/or absence of a CCND1 translocation
would also help to exclude such a possibility, even though they are also not absolute indicators since
rare cases lack cyclin D1 abnormalities. The possibility of an unusual-appearing B-lineage
lymphoblastic lymphoma could also be considered far down on one's list; however, in this case both
the cytologic appearance and presence of surface immunoglobulin would be very unlikely. When dealing
with only paraffin embedded tissue sections, use of a TdT stain is helpful since the vast majority of
lymphoblastic neoplasms are positive.
- Burkitt lymphoma (atypical BL)
- Diffuse large B-cell lymphoma
- B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma
- Primary cutaneous diffuse large B-cell lymphoma, leg type
- Blastoid (pleomorphic) mantle cell lymphoma
- Unusual lymphoblastic lymphoma
Diffuse large B-cell lymphoma (DLBCL)
DLBCL is "a diffuse proliferation of large neoplastic B lymphoid cells with nuclear size equal to or
exceeding normal macrophage nuclei or more than twice the size of a normal lymphocyte." 
One should, however, recognize that there are other types of lymphoma that would also fulfill this
definition and some DLBCL that do not. DLBCL is a heterogeneous entity that includes a number of
different variants and subtypes. A complete discussion of DLBCL is far beyond the realm of this
handout. Only a skeletal discussion is included here. The reader is referred to the references
including our recent review of aggressive nodal B-cell lymphomas.
One should also look
for the 2008 WHO Bluebook when the stork deposits it for an expanded discussion of DLBCL and its many
There are four major morphologic variants of DLBCL that are well described in the WHO monograph:
centroblastic, immunoblastic, T-cell/histiocyte rich (T/HRBCL) and anaplastic.  Although
not recognized in the WHO monograph, another important morphologic variant of DLBCL is the type composed
of often intermediate sized very blastoid-appearing cells.  Some of the blastoid type cases
may also correspond to lymphomas described as being composed of "small centroblasts."
Other variants/subtypes of DLBCL, some of which will shortly become "distinct entities" include
plasmablastic lymphomas, DLBCL with expression of anaplastic lymphoma kinase (ALK), mediastinal large
B-Cell lymphoma, intravascular large B-cell lymphomas, primary effusion lymphoma and DLBCL associated
with chronic inflammation . Each of these lymphomas has its own distinctive, although not necessarily
specific morphologic appearance. Similarly they have distinctive immunophenotypic and
cytogenetic/molecular features but are not further discussed here.
Most but not all DLBCL express the B-cell-associated, but not B-cell-specific, CD20 antigen and/or
other pan-B-cell antigens.
Surface immunoglobulin, if present, is monoclonal but it may
be non-detectable. They are cyclin D1 and TdT negative. The detailed phenotype of DLBCL is variable.
Some cases mark like cells in a follicular lymphoma (CD10+, bcl-6+) and others more
like later B-cells with loss of follicular center cell markers (CD10, bcl-6) and acquisition of
transitional (MUM-1) and overt plasma cell-associated markers (CD138). Bcl-2 is variably expressed.
Some cases express the CD5 T-cell associated antigen. 
DLBCL demonstrate BCL-2 rearrangements in 20-30% of the cases and BCL-6 rearrangements in up to 30%.
A small proportion have
In our experience, classical
cytogenetic studies are successful in about 70% of DLBCL with >90% of those studies demonstrating an
abnormal karyotype. 
Burkitt/Atypical Burkitt Lymphoma (BL)
BL are diffuse, and much less often in part follicular, proliferations of relatively small transformed
cells with amphophilic cytoplasm.  They have an extremely high proliferation fraction,
prominent apoptosis and a "starry sky" appearance. Some cases, usually found in immunodeficient
patients, have plasmacytoid features. Current convention is that Burkitt and atypical Burkitt
(Burkitt-like) lymphomas represent the same entity but with the latter showing more cytologic variation.
The terms atypical Burkitt or Burkitt-like lymphoma are not to be used simply because the cells of a
DLBCL are on the smaller side.
Most BL are surface immunoglobulin positive, CD5-, CD10+, and usually bcl-2- with virtually 100% of
their nuclei Ki-67+, a phenotype shared with some DLBCL.
Cytogenetic studies demonstrate a translocation involving MYC at
chromosome 8q24 and usually either the IgH locus at 14q32 or less commonly either the kappa or lambda
light chain loci at 2q11 or 22q11, respectively. There are usually few other abnormalities.
 It is critical to realize that a MYC translocation is not specific for BL, so that if one is going to use FISH to help document the
diagnosis of BL one should also look for BCL-2 and BCL-6 translocations that at least usually ought to be absent.
Burkitt lymphoma versus diffuse large B-cell lymphoma
Although it is considered very important to distinguish BL from DLBCL to prevent overtreatment of
DLBCL and undertreatment of BL, it can be very difficult, especially in adults, and gold standard
criteria are lacking.
As recently reviewed in the editorial written about the two BL
gene profiling papers, "BL is not…cured by the treatment for diffuse large-B-cell lymphoma,…", and, at
the same time, adults "often do not tolerate very well the side effects" of BL-type therapy.
 Hence, "Diagnostic accuracy is therefore essential to prevent undertreatment or
overtreatment of patients".
The problematic cases usually have many Burkitt-like features but either the
phenotype/genotype/karyotype is too "atypical", the cytologic appearance is beyond that described for
"atypical" BL, or both. Depressingly, Stein and Hummel wrote in 2006 that "at present, there are no
reliable criteria that can be applied to distinguish BL from DLBCL."  Studies that have
addressed this problem either have found only a minority of cases that fulfill all of the typical BL
criteria described above and one study found no adult cases.
Recent gene profiling studies have demonstrated the existence of a molecularly homogeneous group of BL
that are morphologically, phenotypically and even cytogenetically heterogeneous.
While this suggests that the criteria we use to diagnose BL cannot always be relied upon, gene profiling
studies are not standardized and not currently a clinical laboratory test. Furthermore, consistent with
our daily experience, one of the major gene profiling studies also demonstrated the presence of cases
that were "intermediate" between BL and DLBCL, substantiating the existence of a true gray zone.
 The 2008 WHO Bluebook will have a chapter specifically about these cases that seem to have
features intermediate between a BL and a DLBCL.
B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and
Burkitt lymphoma (diffuse large B-cell lymphoma with "high grade" features)
B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma is
characterized as having:
- Some morphologic features of BL including apoptosis
and frequent starry sky although usually with other features unlike BL (larger cells, more prominent
single nucleoli, non-amphophilic cytoplasm)
- A phenotype usually with some features of BL
(CD10+, bcl6+, sometimes bcl2-) but with other atypical but inconstant features (eg, bcl2+ (~50%),
MUM1+, often Ki-67 not >95% although usually >80%).
- MYC rearrangements
present in ~35-50% of cases, sometimes with other translocations as well. BCL2 translocations in ~15% sometimes with MYC.
- MYC translocations
often with non-IG genes and associated with a complex karyotype. This is unlike most BL.
A pragmatic approach to cases with a major differential diagnosis between Burkitt
lymphoma and diffuse large B-cell lymphomas
Our current imperfect modus operandi is to diagnose BL when the morphologic appearance is acceptable
(but not necessarily typical), the phenotype is typical and a MYC but not a
BCL-2 or BCL-6 translocation is present. Most
other cases require a more descriptive diagnosis such as the one used here or a term like "high grade
B-cell lymphoma, not otherwise specified" or DLBCL with "high grade" features with the cases having the
fewest discrepancies from the typical constellation of BL findings being considered closer to a "real"
BL.  In addition, although not a quantitative science and beyond what I can attempt to
impart today, the reality is that some discrepancies also carry less weight than others, especially if
the finding is not entirely convincing, such as possible weak bcl-2 protein expression in an otherwise
typical BL. Once one is dealing with a case with BL at least in the differential, reliance solely on
"biologic markers" (Ki-67>90%, CD10+, bcl-6+, bcl-2-, MYC translocated
but not BCL-2 or BCL-6) seemed to identify a
more homogeneous population of patients, than use of a consensus histologic/immunophenotypic diagnosis.
 However, many of the lymphomas in the BL/DLBCL gray zone region that were not felt to
fulfill the criteria for a BL still had "a phenotypic and/or genetic shift to BL." This study also
highlighted hematopathologists' problems with reproducibly categorizing these types of cases. We would
specifically designate cases with coexistent MYC and BCL-2 and/or BCL-6 translocations as, at least those
with dual MYC and BCL-2 translocations, are
known to be extremely aggressive.
translocations are rarely found in molecularly-defined BL, Hummel, et al, found them more commonly in
their intermediate or non-BL groups and BCL-6 translocations were not found
in molecularly defined BL. 
Therapeutic implications of B-cell lymphoma, unclassifiable, with features
intermediate between DLBCL and Burkitt lymphoma (diffuse large B-cell lymphoma with "high grade"
The best therapy for the DLBCL with some BL-like features remains to be defined, although some report
that cases with some of the BL features do not do well when they receive more typical DLBCL therapy.
Whether finding MYC translocations independent of other
parameters is a prognostic indicator in DLBCL is controversial.
Some of this handout is adapted and/or exerpted from a
recent review article that I co-authored. 
Take Home Messages
everything is what it seems to be in diagnostic hematopathology.
- Reliance on any
single ancillary study to help categorize a lymphoma can be very misleading.
proud and not ashamed of recognizing that a lymphoma has features that do not allow for it to fit neatly
into one of the standard categories.
- The new WHO Bluebook monograph is on its
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- Prakash S, Swerdlow SH. Nodal aggressive B-cell lymphomas: A diagnostic approach. J Clin Pathol. 2007;60:1076-1085.
- Natkunam Y, Warnke RA, Zehnder JL, Jones CD, Milatovich-Cherry A, Cornbleet PJ. Blastic/blastoid transformation of follicular lymphoma: immunohistologic and molecular analyses of five cases. Am J Surg Pathol. 2000;24:525-534.
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