Pathology #07 Mature B-Cell Neoplasm Hussein Al-Sa di Dr. Sohaib Al-Khatib 0 P a g e Thursday 18/2/2016
Our lecture today (with the next 2 lectures) will be about lymphoid tumors This is a little bit long lecture (56 minutes)... but don t get upset, you can finish it like any other lecture. Lymphoid neoplasms are either: Lymphoma: mature cell neoplasm. OR Leukemia: immature (primitive) cell neoplasms However, there re exceptions. An example of that is Hairy cell leukemia which consists of mature B cell lymphocytes But why is it called Leukemia?! Because of the presentation (site of involvement). Previously, they used to classify neoplasms as leukemia if they involve the bone marrow and the peripheral blood, and as lymphoma if they involve lymph nodes. So because hairy cell leukemia involves bone marrow and the peripheral blood, they thought that it s leukemia and kept the name to avoid confusing people. So again Lymphoma tumor of mature cells lymph nodes involvement &it may disseminate to bone marrow Leukemia tumor of immature cells Bone marrow & peripheral blood involvement With some exceptions like the one mentioned above * Lymphoma Lymph: lymphatic tissue oma: mass, so mass arising from the lymphatic tissue. * Leukemia Leuk: white; whitening of the blood because of the many circulating abnormal lymphocytes... so the color of the blood becomes faint red which is whiter emia: blood Example: Follicular lymphoma: It s a lymphoma because it arises from lymph nodes, and because it forms follicles it s called follicular. 1 P a g e
Now if you have a patient with follicular lymphoma and a bone marrow involvement (because as we said lymphoma may disseminate to bone marrow), do we call it follicular leukemia? No we just call it lymphoma with a bone marrow metastasis What if you have a patient with leukemia and lymph node involvement? It s leukemia with lymph node metastasis (not lymphoma). Now let s take a lookat lymph node anatomy (study it carefully) How do you differentiate between the lymph node and any lymphoid tissue? If it has a capsule it s a lymph node, otherwise it s a lymphoid tissue. In the figure you can see: - The capsule. - Beneath the capsule there is a sub-capsular sinus, which is opened to allow lymph to pass through it. - The Marginal zonecontains B lymphocytes. - Mantle Zone - In the Medulla there re sinuses. - The Paracortex area contains T-Lymphocytes - Cortex: containslymphoid follicles which in turn contains B-lymphocytes 2 P a g e
These lymphoid follicles may be active (primitive) or inactive (secondary). How can we differentiate between active and inactive follicles? Through the presence of the Germinal center. If it s present, the follicle is active, if not it s inactive. Why would a follicle to be active? Because of the exposure to antigens, and that leads to its activation along with the germinal center formation. In the germinal center, B lymphocyte maturation, immunoglobulins production and class switching occur. But What is class switching? Our body produces millions of immunoglobulins (IgG, IgM etc.) in response to the unlimited number of antigens it encounters. After the production of these immunoglobulins, there will be a switching from one class to another. Immunoglobulin class switching: is a biological mechanism that changes a B cell's production of immunoglobulin (antibodies) from one type to another, such as from the IgM to the IgG. The antibody retains affinity for the same antigens, but can interact with different effector molecules. (From Wikipedia) All these processes occur in the germinal center. Why is it important to know the anatomy and the structure of lymph nodes? Because Lymphoma is named according to its cell of origin. For example: - Lymphoma arising from lymph node follicle is called follicular lymphoma - Lymphoma arising from mantle zone is called mantle cell lymphoma - Lymphoma arising from the marginal zone is called marginal cell lymphoma. 3 P a g e
We can differentiate between these different types of lymphoma by: looking at the site of expansion of the lymphoma, cellular morphology and antigen expression. For example, cells in the germinal center of lymphoid follicles express antigens different from those expressed on mantle cells: Cells (B lymphocytes) in the germinal center of lymphoid follicles express CD10 antigen. (CD: cluster of differentiation).remember this point Different antigens are given names but it s difficult to remember them since there re many of them, so they re given numbers. T lymphocytes express either CD4 (T helper cell)or CD8 (cytotoxic T cell). So, if you have a tumor composed of lymphocytes and you do CD test. If the cells are CD4 positive, what does that mean? It means that the tumor is composed of mature T lymphocyte, it could be T cell lymphoma or T cell leukemia. There re common markers for T lineage and others for B lineage: (A marker if present on the surface of a cell it tells us what that cell is) 1) The common markers for T linage are: - CD3, it s specific for T lymphocyte - CD4 &CD8 are also markers for T lymphocytes but are NOT specific like CD3 2) The common markers for B lymphocytes are: - CD10 - CD19 - CD20 - CD22 You have to remember these markers. 4 P a g e
? On what cell can you find CD10? On B lymphocyte within lymphoid follicles (germinal center). So as we said follicular lymphoma arising from the lymphoid follicles should express CD10. This is a section of a lymph node Notice: - The germinal center within the lymphoid follicles - Mantle zone - The marginal zone You have many lymph nodes throughout your body. The stage of lymphoma is determined according to the number and sites of lymph nodes involved. If a 10 year old kid with cervical lymph nodes enlargement of one week duration complaining of fever, what should think of? It s Infection! It could be tonsillitis, dental caries, infectious mononucleosis etc. Lymph node enlargement(also called Lymphadenopathy)could be: Monoclonal: tumor (lymphoma) or Reactive: non-monoclonal; nontumorous especially in children if it s localized and acute. Acute or chronic (persistent) Associated or not associated with fever. Generalized or Localized 5 P a g e
If Persistent and Generalized enlargement = you should think of lymphoma or chronic infection. Acute and localized = infection You have to know the classification because it determines what you will do next. For example, that kid with cervical lymph node enlargement, if this enlargement is due to infection (tonsillitis) you may give him antibiotic after doing the culture and swap and see him after 2 weeks. However, if you re thinking of lymphoma, you should do other appropriate procedures. So there re many causes of lymphadenopathy: Not always you have to do biopsy and detailed lab tests you have to have an approach see the diagram next page: If you have a patient with lymphadenopathy, are you going to reassure to the parents?! It depends on the situation: If it s infection you can reassure the family. If it s not an infection, look for significant physical signs and symptoms like sweating, weight loss, generalized weakness, generalized lymphadenopathy (cervical, axillary, abdominal etc.).. These signs are alarming If these signs are present, you should investigate and sometimes you do a lymph node biopsy. If no significant signs and symptoms present, you can observe and use antibiotic, and see the patient again after a period of time. * Usually, painful enlarged lymph node indicates infection, but this is not the rule always. 6 P a g e
yes you can go through this page quickly :3 7 P a g e Definition Lymphoma: is a tumor arising of mature B or T lymphocytes, usually in the lymph nodes
In general, Lymphoma is classified into Hodgkin and non-hodgkin lymphoma. Hodgkin is a name of a scientist - Hodgkin lymphoma has 5 subtypes - Non-Hodgkin lymphoma have many subtypes including B & T lymphoma What causes cancer? Genetic defects, especially those involving translocation between genes on different chromosomes. Knowing translocation is very important because it enable us to confirm the diagnosis. If you look at the table, you can notice that chromosome #14 is involved in most translocation WHY??? Because chromosome #14 harbors a promotor for immunoglobulin H synthesis. 8 P a g e
Recall that one of the identifying characteristic of tumors is its uncontrolled rapid growth. So what drives the normal lymphocyte to be abnormal is a genetic defect that affects the fate of this lymphocyte. Chromosome #14 has a promotor for immunoglobulin H gene which is (the promotor) consistently active to continuously produce immunoglobulins against different antigens that your body encounters through your daily life. Examples: (You have to remember them) Translocation of bcl-2 gene with IgHgenes in t(14:18): On chromosome #14 there s the bcl-2 gene which is an anti-apoptotic gene so this translocation will put bcl-2 gene under the control of immunoglobulin promotor induce the expression of bcl-2 more and more no apoptosis tumor (Follicular lymphoma&dlbcl (Diffuse Large B-Cell Lymphoma)) Translocation of Cyclin D1(bcl-1) gene with IgH gene int(11:14): You put cyclin D (bcl-1) under the immunoglobulin promotor induce cell proliferation Mantle cell lymphoma t(11:18) & t(1:14) Malt lymphoma t(9:14) Lymphoplasmocytic lymphoma Burkitt lymphoma : - t(8:14) - t(2:8) - t(8:22) Also, chromosomes #2 harbor active promotor like that of #14. #14: IgH #2: IgK #22: Igλ So you will find translocation of these chromosomes with other chromosomes. And genes which become under the control of these promoters will be more active tumor. 9 P a g e
B Lymphocytes mature in lymph nodes and bone marrow. T lymphocytes mature in the thymus. We classify leukemia and lymphoma according to their cell of origin. Tumors arising from the germinal center of lymphoid follicles in lymph nodes like: 1- Follicular lymphoma 2- Burkitt lymphoma 3- Diffuse large cell lymphoma Are these cells CD10 positive or negative? They re CD10 positive because they re germinal center lymphoma. What about mantle cell lymphoma, is it CD10 positive? No, because it doesn t arise from the germinal center. Are cells arising from marginal zone positive for CD20? Yes because marginal zone contains B lymphocytes. All B cell lymphoma are CD20 positive. Remember: Tumors arising from immature lymphoidcells called leukemiathis is also applied on lymphoid cells precursors (because they re immature). Acute lymphoblastic leukemia (ALL)is an example. It usually affects children and is curable. Chronic lymphocytic leukemia(cll): it s is leukemia but it s a composed of mature cells! Why? Same reason as Hairy cell leukemia (page 1). These cells arise from a stage before going inside the lymph node called naïve Blymphocyte. It usually affects adults. Recall that lymphocyte start differentiating in bone marrow, then they re released to the blood, and to complete their maturation, they go to lymph nodes. This stage after going out of bone marrow and before going into the lymph node is called naive Blymphocyte. 10 P a g e
After going inside the germinal center, the B lymphocyte matures into Plasma cell which can be present in lymph nodes or tissues but not in blood. A tumor arising from plasma cells is called: Plasma cell neoplasm (E.g. plasmacytoma, multiple myeloma... these arise from plasma cells)? Which one is aggressive and which one is indolent (in behavior) of CCL and ALL? The general rule is: Acute leukemia aggressive; bad with short survival, but if the patient is given the right treatment it may be curable. Chronicleukemia indolent; the patient can survive for years but the disease is non-curable 11 P a g e
B-Cell Neoplasm Again... neoplasm of mature cells are called lymphoma, whereas those of immature cells are called leukemia. But how can we differentiate between differentiated mature and undifferentiated cells? By morphology (like high N/c ratio) and antigen expression. That s why we have to know antigens associated with maturity and those associated with immaturity. For example, CD20: indicates a mature cell, CD3: its expression is early so it could be mature or immature. However, for immature primitive cells, we use 3 markers in general: CD34, TDT, CD117. (TDT is usually seen in acute lymphoblastic leukemia) So a cell expressing CD34 is immature primitive cell, it could be a leukemic or a stem cell. If you see a tumor that consists of cell expressing both CD20 and CD43, is this normal? Definitely no. Normal immature stem cells in our bone marrow express CD34 only. Normal mature cells should express mature markers only. Normal immature cells should express immature markersonly. If you have a cell expressing both abnormal leukemic cell. 12 P a g e
Immature B cell neoplasms In the figure above, there re tumors arising from precursor cells, we call them precursor cell lymphoblastic leukemia/lymphoma. Why lymphoma? Becauseyou can get the same tumor with the same antigen expression involving lymph nodes. So the same disease, if it involves the bone marrow we call it leukemia, whereas if it involves lymph nodes we call it lymphoma. Mature peripheral B cell neoplasms For mature peripheral B cell neoplasm there s B-cell CCL/SLL (chronic lymphocytic leukemia/ small lymphocytic lymphoma). Both of them involve mature cells (mentioned in page 10) So a patient with CLL will present to you with lymphocytosis. It s usually an incidental finding; you find it by chance. For example, if an elderly patient comes to do regular checkup, when you look for white blood count it s 50,000!! This high (leukocytosis) and there s no sign of infection. Then you draw a peripheral blood sample and find that those are mature cells. Then you do flow cytometry (to look for antigens) and find that those cells have mature B cell markers (mature B lymphocytes). How do you know if these cell are abnormal or not? By expression of other antigens. For example, if these B cells express CD5(which is a T cell marker) then this is abnormal clonal growth. CLL mature B cells expressing mature B cell markers but expressing CD5 which is a T cell marker. In small lymphocytic lymphoma SLL, the same disease as CLL but it involves lymph nodes. Just be familiar how the above examples are different and if they involve bone marrow or lymph nodes other examples are either leukemia or lymphoma, so no problem take it easy 13 P a g e
Marginal B cell neoplasm It could be: nodal: marginal zone lymphoma arising from the lymph node. OR Extra-nodal: marginal zone lymphoma arising from the spleen for example, we call it splenic marginal zone lymphoma. Follicular lymphoma: so called because it forms follicles Mantle B cell lymphoma: It arises from mantle zone. Diffuse large B cell lymphoma: If you look at the cells under the microscope you will see it s diffused, not forming nodules, and composed of large B lymphocytes. Previously, pathology was just a descriptive science; you see and describe, but now there re many bases for classification (E.g. genetic defects). Low grade B-cell NHL (non-hodgkin lymphoma) Includes marginal zone lymphoma, follicular lymphoma (stage 1), CLL and SLL. Small Lymphocytic Lymphoma SLL - so called because it is composed of small mature B lymphocytes - it s a low grade lymphoma - has a diffuse growth pattern; sheets of lymphocytes - If you look at a normal lymph node, you expect to see capsule, sub-capsular sinus, germinal canter, lymphoid follicles. However, if the lymph node is involved in SLL, you will see diffuse effacement of its architecture by sheets of lymphocytes. All what you see is lymphocytes, you don t see follicles... most of the lymph node is effaced by small lymphocyte... see next 14 P a g e
Capsule Here, in a normal lymph node you should see follicles, but the total architecture is replaced by small lymphocyte. (Refer to page 5 to see the normal LN). This is in case when small cells replace the architecture of a lymph node. On the other hand, if the cells are large we call it diffuse large B cell lymphoma Higher magnification As you see, all lymphocytes look mature, sometimes you may see some abnormal pro-lymphocytes. Looking at this image, by morphology, you can t differentiate between normal and lymphoma lymphocytes. So what will you do? You will look for architecture and antigens. You look for antigens using immune stains, by applying antibodies. If the antigen is there you will get antigen-antibody reaction and the stain will appear. These are peripheral blood cells. Also you can see mature-looking lymphocytes These are Smudge cells which are remnants of cells that lack any identifiable cytoplasmic membrane or nuclear structure. labce.com/spg48905_smudge_cells.aspx SLL is a B cell lymphoma, so it should express CD20 for example, and it doesn t arise from the germinal center. So if you do a CD10 test it should be negative for CD10 because it s not a germinal center lymphoma. There re also other markers that are specific for SLL: CD5 and CD23. 15 P a g e
If a patient presented to you with more than 5000 lymphocytes in peripheral blood CLL But if a patient presented to you with the same disease with less than 5000 abnormal lymphocytes in peripheral blood and no bone marrow involvement SLL?If you want to know if a lymphocyte cell resulted monoclonal or polyclonal process, what dowe do? We look for Kappa (K) and Lambda (λ) light chains. - Normally in your body, there should be lymphocytes having K and others having λ polyclonal = normal - If all cell are expressing K or all cells are expressing λ this is abnormal monoclonal (Neoplastic) - Another example: In your peripheral blood you should have CD4 T cells and CD8 T cells too, but if all of the cells are CD4 abnormal: these clonal (neoplastic) cells replaced all other cells. As we said, these B cells express CD5 which is a T cell marker (due to genetic defect) By knowing all of the information above, we can that this is a small lymphocytic lymphoma or chronic lymphocytic leukemia 16 P a g e Remember: SLL & CLL are the same but differ in the site of involvement + # of lymphocytes in the peripheral blood
In lymphoma, bone marrow is invariably involved: less than 30% involvement If there s more than 30% bone marrow involvement Leukemia Typically, the patients are elderly with generalized lymphadenopathy and mild to moderate hepatosplenomegaly. B-Cell Chronic Lymphocytic Leukemia (CLL): - As we said it s the same disease as SLL. - Neoplasm of mature lymphocytes - Accumulation of mature B-lymphocytes in BM or PB - Epidemiology: Most common leukemia in West 30% of all leukemia Older adults (median age 70 y) CLL Clinical Features& pathology : Lymphadenopathy, Thrombocytopenia, Anemia etc. Peripheral blood: Lymphocytosis >5,000 per μl (CLL lymphocytes) Or >30% bone marrow involvement CD10-(because it s a non-germinal center lymphoma), CD19+, CD20+, CD23+, CD5+, sig+ (clonal) - Anemia, Thrombocytopenia 17 P a g e
Transformation from low grad (indolent) to high grade (aggressive) lymphoma is possible, it s called Richter transformation. For CLL, it may transform into aggressive lymphoma which is Diffuse large B cell lymphoma: If you have a 70 year old patient, and you diagnose him with chronic lymphocytic lymphoma, and the patient is okay because this is chronic indolent disease. However, this patient may come to you after 3 years complaining of weight loss, fever, sudden lymph node enlargement. You then look at the peripheral blood sample and you see a new lymphoma composed of LARGE cells The reason behind this is that additional genetic defects occurred in addition to the base one and that caused transformation of CLL into diffuse large B cell lymphoma. Done Good luck and do your best Edited by Farah Bani Hani 18 P a g e