Hematologic Malignancies VI: T-cell and NK-cell lymphomas Flashcards
T or F. T-cell and NK-cell malignancies are relatively poorly understood in comparison to B-cell malignancies.
T.
While B-cell malignancies which appear to derive from well differentiated cells are in general less aggressive, no such correlation is seen with T-cell malignancies
While B-cell malignancies which appear to derive from well differentiated cells are in general less aggressive, no such correlation is seen with T-cell malignancies
There are no simple recurrent themes in T cell malignancies, unlike B-clel malignancies.
Most do NOT involve translocation of an oncogene to a T-cell receptor promoter (No simple analogy to B-cell lymphomas)
Many show complex karyotypes
Only a few have been genetically defined
What is one useful genetic tool in diagnosing T cell diagnosing
TCR Clonality can often be demonstrated by PCR-based studies of the T-cell receptor gene.
does not apply to NK cells
T or F. Clinical presentation of T-cell malignancies is highly variable
T.
What organs are affected in ALK+ (ALK gene fuses to one of several partners) Anaplastic large cell lymphoma? Most to least
- *lymph nodes
- liver, soft tissues
- bone marrow and cortex
- skin
- peripheral blood
What organs are affected in Angio-immunoblastic T-cell lymphoma? Most to least
- lymph nodes
- skin, bone marrow, spleen, GI tract
What organs are affected in Mycosis fungicides? Most to least
- skin
- lymph nodes, spleen, liver
some peripheral blood involvement (Sezary)
Mycosis fungicides immunophenotype?
its immunophenotype approximates that of a helper T-cell, i.e. it expresses CD4 and – usually – other T-cell antigens like CD3.
so they are CD3/4/and 5+
But it tends to not express the complete package of 4 or 5 normal T-cell antigens – and identifying T-cells that lack one or more of them is one of the ways in which we make this diagnosis.
What is Sezary syndrome?
A subset of mycosis fungoides – specifically, the term applies to those MF cases in which there is significant peripheral blood involvement.
How does mycosis fungoides present clinically?
Patchy, flat red skin lesions that can progress to thick, psoriasis-like or ulcerated lesions;
can involve bloodstream (“Sezary Syndrome”), usually in elderly patients
Normal counterpart of mycosis fungicides?
CD4+ T cells
Morphology of mycosis fungicides?
- Cytology: normal size lymphocytes with indented nuclei
- Tissue: Bland looking lymphocytes that invade the epidermis in clusters (called “Pautrier micro-abscesses”, although they really are not abscesses)
- Bloodstream: bland lymphocytes with “cerebriform” nuclei
Genetic cause of mycosis fungoides?
clonal re-arrangement of T-cell receptor gene
The Paltrier micro-abscesses seen in mycosis fungoides are also common in what?
Nothing BUT It can be hard to distinguish this kind of lesion from some kind of chronic inflammatory/reactive condition.
In the latter, though, the T-cells present will (on molecular analysis) usually contain a variety of re-arranged T-cell receptor genes. In MF, as in other T-cell malignancies, one clone is predominant – so just one rearranged form of the T-cell receptor will be present. We often have to analyze this in order to be sure of the diagnosis.
What is Peripheral T-cell lymphoma NOS?
Currently make up about 30% of T-cell lymphomas
garbage category of “not otherwise specified”
Clinical symptoms of Peripheral T-cell lymphoma NOS?
Diffuse lymphadenopathy
B symptoms (fever, night sweats, weight loss)
paraneoplastic features
eosinophilia
pruritis
hemolytic anemia eosinophilia
Normal counterpart in Peripheral T-cell lymphoma NOS?
unclear
Involved sites in Peripheral T-cell lymphoma NOS?
just about anywhere but usually NOT blood stream
Diagnosis of Peripheral T-cell lymphoma NOS depends on what?
the pathologist’s basic microscopic skills.
If the normal architecture is effaced, AND a collection of cells showing similar histologic characteristics are present, AND those cells don’t show the cohesive, gland-forming architecture typical of a carcinoma, we look into whether this could be a T-cell lymphoma.
In the cases shown, most pathologists can pick out a population of cells that is just too uniform for normal paracortex.
Usually lymph themes of Peripheral T-cell lymphoma NOS?
expanded paracortex and effacement of normal architecture
BUT clusters of “epithelia histiocytes” usually seen near the cortex (paracortical) is possible
Some T-cell malignancies also show a proliferation of cells with large amount of eosinophilic cytoplasm, a cohesive kind of clustering, and normal looking nuclei These “epitheiiod histiocytes” are a clue to the presence of a T-cell malignancy, particularly if they are more prominent near the capsule of the node.
Some T-cell malignancies also show a proliferation of cells with large amount of eosinophilic cytoplasm, a cohesive kind of clustering, and normal looking nuclei These “epitheiiod histiocytes” are a clue to the presence of a T-cell malignancy, particularly if they are more prominent near the capsule of the node.
Immunophenotyping usually completes the diagnosis of Peripheral T-cell lymphoma NOS. What will it look like?
What’s expected: CD3, 5, 7, and 4 or 8
What’s usually seen: Loss of one or more of the above
Variants:
“Double positives” (CD4+, CD8+)
unexpected markers:
1) CD20 (B-cell marker)
2) CD56 (macrophage /monocyte marker)
3) CD30 (R/S cell marker)
Genetics of Peripheral T-cell lymphoma NOS?
Complex karyotype:
Multiple chromosomal gains and losses
Multiple chromosomal deletions
No pattern has emerged
Clinical course of Peripheral T-cell lymphoma NOS?
aggressive with 5 yr survival 20-30%
What is Angioimmunoblastic T-cell lymphoma (AITL)? Original cell type?
This is one of the better characterized T-cell lymphomas. The immunophenotype of these cells corrresponds to a particular class of normal mature T-cells, the T-follicular helper cells.
not on exam
Clinical presentation of AITL?
Rapidly progressive critical illness
- Diffuse lymphadenopathy
- Hepatosplenomegaly
- Skin rash
- cold autoimmune hemolytic anemia
- Evidence of immunocompromise
These usually present to us with widespread, rapidly progressing disease.
Normal counterpart in AITL?
follicular T-helper cells
Involved sites in AITL?
lymph nodes
spleen, liver
bone marrow
skin
Lymph node morphology in AITL?
normal/reactive lymph node
involvement of multiple superficial lymph nodes
What we typically see is “effacement of normal architecture”, although occasional germinal centers are typically still present.
The node is enlarged by an expansion of the paracortex.
Unfortunately, the paracortex in reactive/ infectious conditions shows a great deal of variation in cell content, and it normally contains occasional lymphoid cells with large nuclei and prominent nucleol (“immunoblasts”).
So finding those “angry looking” features at high power is not helpful. What we do see in this case is an unusual expansion of small paracortical vessels, often with a dense eosinophilic material thickening their walls, and a larger number of immunoblasts than is typical of reactive conditions
Immunophenotype of AITL?
Immunostains:
- Excess CD10+ cells in paracortex (B cells are not usually common in the paracortex!!!)
- Residual FDC networks (CD21+)
Flow: CD3+, CD4+, CD10+
Follicular dendritic cels (FDC) present antigens to B and T cells in germinal centers, and their processes form a kind of meshwork within the GCs. In most cases, if the GC’s are gone, an immunostain for the FDC’s (CD21) shows that they are gone too. In the case of AILT, they are suprisingly NOT absent; ghosts of germinal centers can be identified, another key clue to a diagnosis of AILT.
Follicular dendritic cels (FDC) present antigens to B and T cells in germinal centers, and their processes form a kind of meshwork within the GCs. In most cases, if the GC’s are gone, an immunostain for the FDC’s (CD21) shows that they are gone too. In the case of AILT, they are suprisingly NOT absent; ghosts of germinal centers can be identified, another key clue to a diagnosis of AILT.
Finally, flow cytometry can anil down the diagnosis by showing a large population of CD10+ T-cells. In normal and reactive nodes this population is too small to be clearly identified by this method.
Finally, flow cytometry can anil down the diagnosis by showing a large population of CD10+ T-cells. In normal and reactive nodes this population is too small to be clearly identified by this method.
Genetics of AITL?
Complex karyotype:
Multiple chromosomal gains and losses
Multiple chromosomal deletions
No pattern has emerged
Clinical course of AITL?
Aggressive
Median survival less than 3 years
The prognosis is poor, and standard chemotherapeutic agents have a high morbidity rate in AILT because their immunocompromising side effects are compounded by the immunocompromise inherent to the disease itself.
