MP

Question 1

Lymph node structure?

Answer 1

Cortex—> contains B cell follicles.
Paracortex—> contains mainly T cells.
Medulla—> contains mainly macrophages and mature B cells (plasma cells).

The B cells in the cortex can be primary or secondary. Primary follicles contain naive B cells that are mature but haven’t encountered the antigen yet. When B-cells encounter the antigen, primary follicles are replaced by secondary follicles. Secondary follicles are characterized by a germinal centre surrounded by a mantle zone.

Question 2

What is follicular hyperplasia?

Answer 2

Follicular hyperplasia is a hyperplasia of the germinal center. The different markers characterizing germinal centers are : Bcl6 a TF, CD21 or CD23 highlights the cytoplasmatic meshwork of follicular dendritic cells, CD4 a marker for TFH.
The dark zone of the germinal centre is characterized by high proliferation index Ki-67.

Question 3

What is paracortical hyperplasia?

Answer 3

The marker used to stain these T cells is CD3.
Causes of paracortical hyperplasia are stimuli that trigger T-cell mediated immune response:
- Drugs (e.g., antiepileptic agents such as diphenylhydantoin).
- Foreign material (tattoo ink, anthracotic pigment due to pollution).
- Post-vaccination • Clearance of endogenous material (macrophages).

Question 4

What is sinus histiocytosis?

Answer 4

Sinus histiocytosis refers to an increase in the number and size of cells lining lymphatic sinusoids, including intrasinusoidal macrophages (histiocytes). These cells lead to an expansion and distension of the sinuses.
Generally caused by draining cancer, especially in inguinal or breast cancer. Another cause could be the presence of anthracotic pigment within the macrophages.

Question 5

What are granulomas?

Answer 5

A granuloma is a collection of macrophages or histocytes, which are very big cells with abundant cytoplasm. In the pictures, you can recognize the presence of granulomas by their “pinkish” appearance and size.
It is important to see if the granuloma is necrotizing or not, in order to understand the aetiology.

A necrotizing granuloma with giant cells is typically seen in tuberculosis, while in sarcoidosis usually they are not necrotic and have no giant cells.

Question 6

What is Hodgkin’s lymphoma?

Answer 6

It is a rare neoplastic disorder. The key feature is that the neoplastic cells represent the vast minority of the tissue, less than 1%. Normally HL is a lymph node based disease as primary extra nodal HL are extremely rare.
HL can only be diagnosed when neoplastic cells are embedded in their proper micro environment.
The prognosis of the disease is generally favorable, up to 80% of patients are cured.

Question 7

What are the different subtypes of Hodgkin’s lymphoma according to the WHO?

Answer 7

• Classic HL—> most prevalent one (85-90%), with four different subtypes:
- Nodular sclerosis, most frequent.
- Mixed cellularity.
- Lymphocytic rich.
- Lymphocyte depletion.
• Nodular, lymphocytic predominance, least frequent (10-15%).

Question 8

What are the characteristics of Hodgkin’s lymphoma, classic type?

Answer 8

The neoplastic cells are called Reed Sternberg cells, but we may also find their mononuclear variants. RS cells are large cells characterized by abundant cytoplasm, multiple nuclei and prominent eosinophilic nucleolus.
Finding RS cells is necessary but not sufficient to perform the diagnosis of HL. Together with RS cells we must find a correct micro environment characteristic of HL.

HL has the critical property of not skipping lymph nodes throughout the route of its spread.

Question 9

What is the micro environment of classic Hodgkin’s lymphoma composed of?

Answer 9

Important components of the classic-type HL are T-cells (CD4>CD8), eosinophils, plasma cells, histiocytes (CD68R+) and the stroma. Some R-S cells may show a more condensed nucleus, a dark cytoplasm and the absence of nucleoli, these are called mummified cells and are the apoptotic counterpart of R-S cells.

Question 10

Possible symptoms of Hodgkin’s lymphoma?

Answer 10

Some patients are asymptomatic, some other show what we call B-symptoms :
• Pruritus.
• Weight loss.
• Night sweats.
• Pain following alcohol ingestion.
• Fever.
• Prominent eosinophilia, tissue eosinophilia is not pathognomonic for HL, but is generally suggestive.

Question 11

What are the different subtypes of classic Hodgkin’s lymphoma characterized by?

Answer 11

Nodular sclerosis—> lymph node stromal reaction can be seen in some cases, therefore we may have sclerosis caused by deposition of poorly cellular fibrotic tissue. Sclerotic bands will appear birefringent under polarized light.

Mixed cellularity—> presents a variation in proportion of neoplastic RS cells, not the classic 1%. Must rule out sclerosis to confirm this diagnosis as it could alter proportions.

Lymphocytic rich—> neoplastic cells are rare but there are many lymphocytes and no sclerosis.

Lymphocyte depletion—> the micro environment where the RS cells are embedded contains less lymphocytes than expected. This type odd HL is characterized by many R-S cells presenting with fibrotic background.

Question 12

How is Hodgkin’s lymphoma confirmed immunohistochemically?

Answer 12

RS cells should be positive for CD30, CD15 and PAX5, and negative for CD45, CD3, CD20 and ALK1.

In the micro environment we should find T cells with a prevalse of CD4+ over CD8+, polyclonal plasma cells and histiocytes which are CD68R+.

Question 13

What do Hodgkin’s lymphoma positive and negative markers represent?

Answer 13

CD30–> all RS cells are stained, it must be strongly expressed. Present only in membranes and golgi apparatus.
PAX5–> B cell marker.
CD15–> marker of myeloid cells. Expressed in RS cells but not always positive.

CD20–> marker of B cells
CD3–> marker of T cells
CD45–> leukocyte common antigen, expressed by WBC not by RS cells.
ALK1—> anaplastic lymphoma kinase 1. Expressed by some tumors and anaplastic large cell lymphoma. Used as DDX between HL and ALCL.

Question 14

What is the origin of RS cells? What are some markers and signaling pathways typical of them?

Answer 14

They are B lymphocytes that have undergone incomplete differentiation, in fact they do not express surface immunoglobulins. Typically B cell that do not express surface immunoglobulins are eliminated.

CD30—> receptor fo TNF superfamily found on the cell surface, able to activate NfKB pathway promoting cell survival, inflammation, proliferation and malignant transformation.
LMP1—> late membrane protein 1 is associated to EBV infections. The expression of this protein gave rise to the hypothesis that HL and the EBV virus could be associated, in fact 35-45% of immunocompetent patients present EBV nuclear integration.
IL-13—> it is able to stimulate proliferation in an autocrine fashion, since R-S cells are able to secrete IL-13 but also express its receptor.
Inactive Fas-Fas ligand system—> R-S cells avoid apoptosis by inhibiting the Fas-Fas ligand interaction. This is ultimately why these cells do not die despite the lack of surface B-cell receptor.
GM-CSF—> neutrophils are recruited by GM-CSF which is produced by RS cells. This can be seen on a BM biopsy showing myeloid hyperplasia and megakaryocytic hyperplasia.

Question 15

What is nodular, lymphocytic predominance HL characterized by?

Answer 15

The neoplastic cells are called lymphohistiocytes or popcorn cells which are mononuclear with evident but less prominent nucleoli with respect to RS cells.
Micro environment differently from classic HL is prevalent LV composed by B lymphocytes, CD20+, and histiocytes, more prominent than classic HL.

At immunohistochemistry, pop-corn cells should have: CD45+, CD20+, CD30-, CD15- and CD3-. Opposite of RS cells.

Question 16

What are some important concepts of nodal non Hodgkin’s lymphoma?

Answer 16

• Lymphomas are the solid counterpart of hematological tumors but they must not be approached in the same way as solid tumors. Dysplasia -meaning a disorganised growth and precancerous condition- is not present in lymphoproliferative disorders.
• Lymphomas don’t show a recognizable, pre-lymphomatous state like solid tumors. This means a screening test cannot be performed to catch it before it develops.
• Grading is used to measure the degree of differentiation. The concept of grading does not apply to lymphomas and there are no “well differentiated” and “poorly differentiated” lymphomas. There is, however, an exception represented by follicular lymphomas.
• Spread through the body is called localization and not metastasis.
• Definition between lymphoma and leukemia is often quantitative. Some lymphoidneoplasms can be called sometimes leukemia or lymphomas.

Question 17

What is leukemic involvement?

Answer 17

Sometimes cells from lymphomas may access the blood flow and show a small number of circulating neoplastic cells in peripheral blood. A lot of lymphomas have a circulating counterpart, but the definition of leukemic involvement relies on a quantitative cut-off.

Leukemic involvement of lymphoma is a very bad prognostic factor but fortunately is rare, so it is accurately assessed by measuring the number of circulating lymphocytes to see if it exceeds the threshold level.

Question 18

What is the definition of a lymphoma?

Answer 18

The current definition of lymphoma is: lymphoid neoplasia in which tumoral cell features frequently recapitulate those of the individual physiological properties of individual cells at the particular stage of lymphoid development.

Question 19

What is ontogeny?

Answer 19

B cell ontogeny—> B cells arise from the bone marrow as immature cells. Each normal precursor cell has a hypothetical corresponding neoplastic transformation giving rise to a type of lymphoma. So it is not a matter of differentiation but rather development within the stage of maturation.

T cell ontogeny—> same concept applies.

Question 20

What are the categories of lymphomas?

Answer 20

• B or T cell precursors.
• Mature B cell lymphoma.
• Mature T or NK cells lymphoma.
• Hodgkin lymphoma.

Since in the lymph nodes we have other types of cells, these four categories do not exlude the possibility of having other lymphoproliferative disorder.
Additional categories include :
• Immunodeficiency associated lymphoproliferative disorders.
• Neoplasms of histiocytes and dendritic cells.
• Mastocytosis.

Question 21

Frequency of WHO histotypes?

Answer 21

There are different histotypes according to WHO classification. This list refers to western countries so we need to take into consideration that in other parts of the world the frequency’s might be different.

Nearly 50% of cases are represented by just to histotypes, DLBCL and follicular lymphoma.

Question 22

What is follicular lymphoma? Morphological features?

Answer 22

It represents about 1/5 of non Hodgkin lymphomas and it’s usually diagnosed during the adult age with a slight female prevalence. The sites of involvement are usually lymph nodes. In 60% of cases is already disseminated at the time of diagnosis, in fact it is frequently asymptomatic. A clinical manifestation of the disease, however, might be lymphoadenomegaly.

Morphologically we find nodules that resemble follicles composed of a mixture of centrocytes and centroblast but in different proportions.
- Centroblasts are large cells with nucleoli which are sticking to the inner portion of the nuclear membrane and with acidic nuclei.
- Centrocytes instead are smaller, indented and irregular.
Both types of cells must be recognized in order to perform the diagnosis of follicular lymphoma.

Question 23

What are centroblasts and centrocytes?

Answer 23

A centroblast refers to an activated B cell that is enlarged and rapidly proliferating in the germinal center of a lymphoid follicles. Morphologically they are round to oval large cells containing 2 to 3 nucleoli.

A centrocyte refers to a B cell with a cleaved nucleus. They are relatively similar in size but lack the distinct nuclei and are more irregularly shaped.

Question 24

How do we differentiate follicular lymphoma from hyperplasia?

Answer 24

Firstly we need to confirm the presence of B cells. The first marker to look for is CD20 followed by Bcl-6 and CD10. Staining for Bcl-2 should be negative for reactive centers an positive for neoplastic proliferations.
If for some reason it is negative but you are convinced it is neoplastic you can do FISH. It can also be useful to see the index of proliferation as it will be lower in the neoplastic proliferation than in the reactive.

Question 25

What is a diffuse large B cell lymphoma? Morphology? Immunophenotypes? Cytogenetics?

Answer 25

It is the most frequent lymphoma. Median age is 70. 40% of cases aeries outside the lymph nodes like breast and testis. Prevalently male disease. Morphologically there is the complete replacement fo tissue architecture by large cells that sometimes have : the appearance of centroblasts or immunoblastic cells, less frequently T-cell/histiocyte rich and finally could also be anaplastic, very large cells. B cells express CD20+, CD79a+ and negative for CD3-. There can also be positivity to CD10, Bcl-2 and Bcl-6. Less than 5% of DLBCL are CD20-, but that is why it is important to check other markers. In almost 20-30% of cases, DLBCL carries t(14,18) translocation.

Question 26

What are the different categories of DLBCL?

Answer 26

- Germinal center type—> expressed molecules corresponds to molecules that are physiologically expressed by B cells in the germinal center. CD10+ or CD10- with Bcl-6+ and MUM1-. - Activated B cell type—> expressed molecules do not deal with germinal center at all. CD10- and Bcl-6- or CD10-, Bcl-6+ and MUM1+. - Undetermined type—> intermediate expression which cannot be identified by immunohistochemistry.

Question 27

What is a high grade B cell lymphoma?

Answer 27

The WHO introduced this new category of aggressive B cell lymphoma and it is composed of. - Intermediate category—> intermediate morphological features between DLBCL and Burkitt’s lymphoma. - Blastoid—> smaller B lymphocytes with immature appearance. The main DDX are lymphoblastic lymphoma and blastoid variant mantle cell lymphoma. - DLBCL like—> morphology and immunophenotype resemble DLBCL

Question 28

How c an we differentiate between DLBCL and HGBCL?

Answer 28

FISH analysis is performed. HGBCL by definition has rearrangement of C-Myc. Immunohistochemistry can also be used to detect C-Myc rearrangement although positivity is not enough for diagnosis and must be confirmed with FISH. Negative immunohistochemistry is enough to stop diagnosis process. In fact, among 50 patients that were positive in immunohistochemistry, just 10 fish was positive.

Question 29

What is peripheral T cell lymphoma? Morphology? Markers?

Answer 29

They account for 50% of all T cells abnormalities. It is mainly a nodal disease, but they have also an extra nodal involvement (less than DLBCL but much higher than Burkitt). It is very often symptomatic as there is the production of cytokines that leads to symptoms like fever. In T cells lymphoma one possible paraneoplastic phenomenon is hypercalcemia, typical of tumors like multiple myeloma. There are intermediate-large lymphocytes and there is the coexistence of non-neoplastic components, including plasma cells, histiocytes, eosinophils. In addition, it displays increased vascularization. It shows negativity for CD20 and positivity to all T cell markers including CD2, CD3, CD5, CD7 and CD45RO. The most important one is CD3, but also CD4 and CD8, which represent two subpopulation of T helper cells. A peculiar aspect of T cell lymphomas is the antigen loss. While a normal T cell is expected to express all T cell markers, neoplastic cells do not equally express all these markers.

Question 30

What is an angioimmunoblastic T cell lymphoma?

Answer 30

It is characterized by prominent vascularization and presence of immunoblastic like cells that are much larger than surrounding cells. Their peculiarity is that they are B cells and not T cells, therefore they are CD20+ and often also EBV+. Sometimes it can occur that you treat your patient for T cell lymphoma and later he develops DLBCL.

Question 31

What is small lymphocytic B cell lymphoma and chronic lymphocytic leukemia?

Answer 31

They are the same disease but in CLL the cancerous cells are found mostly in the blood and bone while in SLL the cancerous cells are mostly found in the lymph nodes. It is an indolent slow growing disease typical of very old people. It is usually asymptomatic but can present with fatigue and small multiple lymphadenopathies. Diagnosis is done with peripheral blood samples except for patients with lymphocytosis and lymphadenopathy. In these cases lymph node biopsy is performed. In the tissue there are some areas referred to as proliferation centers, in which the cells are larger and called pro-lymphocytes. They are basically the site of production of the lymphocytes. This lymphoma has a particular phenotype as it expresses CD5 which is a T cell molecule. It can be strongly expressed or co expressed and weakly positive. It also expressed CD24, CD21 and CD23.

Question 32

What is mantle cell lymphoma?

Answer 32

Very serious disease as it grows progressively. It is mostly nodal based disease. Clinical features resemble CLL or follicular lymphomas.

Question 33

What is mantle cell lymphoma?

Answer 33

Very serious disease as it usually discovered in advanced stages. The cells appearance makes it a challenge to diagnose as it is similar to lymphocytic lymphomas. Therefore immunohistochemistry is very important. Since there are B cells is is CD20+ and CD5+. What is peculiar that is important for diagnosis is CD23-. Final diagnosis is done with a marker called cyclin D1.

Question 34

How are marginal zone lymphoma divided?

Answer 34

Extra nodal - MALT—> most frequent is primary gastric. Splenic—> intermediate in terms of frequency. Nodal—> least common. Since they arise from marginal zone B cells which then migrate and mature in marginal zones. They can give rise to neoplastic proliferation in the GI, thyroid, spleen, brain and lung.

Question 35

What is MALT? Where is it found?

Answer 35

MALT stands for mucosa associated lymphoid tissue. Physiologically it is found in the terminal ileum and in the bronchus where it is called bronchus associated lymphoid tissue. When you have inflammation you develop MALT and it remains throughout your life.

Question 36

How do we recognize a MALT lymphoma?

Answer 36

- Neoplastic cells—> centrocytic like cells, monocytoid cells and a small fraction of small lymphocytes. - Reactive germinal center—> hallmark of a previous inflammation. - Infiltrating T cells. - lymphoepithelial lesion—> T cells sometimes engage and attack the destroyabel part of the epithelium forming this lesion. Immunophenotypically it is different from many lymphomas as it is CD5-, CD23-, CYC D1- and CD10-.

Question 37

Pathology of MALT lymphomas?

Answer 37

In MALT-lymphomas we can have translocations like t(11;18) which is the most common, t(1;14) which is rare and t(14;18). These translocations act directly upon the activation of NF-kB which is responsible for the resistance to antibiotics. We can identify 2 subsets of MALT lymphomas : -One which is responsive to H. pylori, which is negative for t(11;18), the vast majority, but there is more chance to develop multi-hit approaches, so may develop DLBCL. - The other is less responsive to antibiotics but with much lower chances to develop hybrid transformation. This group is more stable from a genetic standpoint so don't develop ever DLBCL.

Question 38

Primary CNS lymphomas? Diagnosis? Immunohistochemistry?

Answer 38

Most of these tumors are characterized by DLBCL histology and they are quite difficult to differentiate them from a common DLBCL because they are both composed of large cells. One important clinical features is that primary CNS lymphomas almost never leave the CNS. The problem is that given the anatomical location of these lymphomas they are very harmful since you may have compression of the brain stem, the respiratory centre or the cardiac centre. Diagnosis is done through biopsy, specifically stereotactic biopsies. Corticosteroids are very effective in reducing pain and are necrotic for the lymphoma as lymphocytes are very sensitive to corticosteroids. CNS lymphomas are positive for MAN1 and BCL6.

Question 39

What is reactive perivascular lymphoid T cell infiltration?

Answer 39

It is a growth path of CNS lymphomas. It occur around a blood vessel. It is characterized by a ring of small lymphocytes CD+ and presence of neoplastic cells CD20+.

Question 40

What is mediastinal large B cell lymphoma with sclerosis?

Answer 40

It is a particular type of DLBCL which is not classified among common types. It is kept separate as it usually grows locally and represents an emergency due to mediastinal syndrome, which is caused by a mass compressing the mediastinal structures. Histologically it is characterized by large infiltrating B cells in the mediastinum, presence of fibrosis and sclerosis, B cell lymphomas.

Question 41

What are ocular adnexal lymphomas?

Answer 41

The ocular adnexa is the structure surrounding the eyeball. The eyeball will be the site of involvement of lymphomas. Usually there are a lot of large B cell lymphomas in the eyeball and they are associated with CNS lymphomas. It is an indolent lymphoma.

Question 42

Association between tumors and chlamydia?

Answer 42

Chlamydia has some biological properties that led to the suspicion that they could be oncogenic in some way : when put in culture, chlamydia can induce activation and proliferation of cells. C. Trachomatis causes trachoma and can also cause genital tract infection. C. Pneumonia causes pneumonia. C. Psitacci causes psittacosis and very aggressive pneumonia. 80% of patients actually has chlamydia DNA within the tumor.