Lets be absolutely clear, the naming system of the different types of blood cancer sucks. Lots of three letter acronyms that don’t even follow the same naming pattern for all sub types. As I explained in an early post on this site “What is blood cancer?” the classification of blood cancer is based on which cell type the cancer cells originated from and in many cases what they look like under the microscope.

You can see on the diagram above where the different names come from. Don’t worry you won’t be tested! But crucially for today’s post you can see that a huge number of different types of blood cancer all come from the B lymphocytes. This includes almost all Hodgkins and non-Hodgkins lymphomas (with the exception of the rare T-cell and NK lymphomas) and one of the leukemias, CLL (Chronic Lymphocytic leukemia).

Lets call all these subtypes of lymphocyte blood cancer for the sake of clarity. The lymphocytes are designed to mutate during their maturation phase so that the body can produce many different types of antibodies. They are also designed to grow really rapidly when their antibody is needed. It is perhaps no wonder that lymphocytes can be the source of so many very different types of blood cancer. Some of these are acute aggressive and fast growing. Others are chronic, indolent, and slow growing.

One type of blood cancer that seems to cause a lot of confusion has two names – Small lymphocytic lymphoma (SLL) and chronic lymphocytic leukemia (CLL). For more than twenty years what was once thought to be two different diseases has been considered as one. And to make matters worse this disease is both a leukemia and a type of non Hodgkins lymphoma (NHL). No wonder it gets confusing. Recently on a forum I discovered one person who had understood that their doctor had told them they had four separate types of blood cancer leukemia, CLL, SLL and NHL. That must have been worrying! In reality this is all the same disease.

Unfortunately some of the patient information pages on patient charity websites don’t make this point as clearly as we would like. But below I will share some more explanations of this and include quotes and links to peer reviewed official medical journal articles that explain this point and refer to the WHO definitions of CLL and SLL.

• CLL = blood + bone marrow + nodes (though can be blood mostly and some don’t have node growth) 
• SLL = nodes + bone marrow (though can be nodes only). If you have CLL it includes any growth you have in the nodes and so if you like the CLL diagnosis supercedes and replaces the SLL diagnosis

It’s amazing to me how even some doctors seem to get confused with all this, or at least communicate in a way that is confusing to their patients. It’s very possible that many people with CLL originally had cancerous lymphocytes that started to grow in lymph nodes. Under the microscope of these cells look small and so if found in a lymph node will be described as having the appearance of “small lymphocytic lymphoma”.

But when those cells spill out into the blood and grow there as well then we call them same disease CLL. It’s really a lymphoma that wants to be a leukaemia in most people. So it’s not possible to have both diagnoses at once. If you have it growing in your blood even what’s in your lymph nodes is called CLL. But some people start with if just in the nodes, and so are diagnosed with SLL, but it later moves into the blood and so the diagnosis gets changed to CLL.

So you might have had SLL that then developed into CLL but by definition you can’t have both. If you have the cancerous lymphocytes growing in your blood at a level of above 5(thousand) then even those that are also growing in the lymph nodes are also classed as CLL. Confusing I know but that’s the way it is. It’s only called SLL if it isn’t in the blood. I get that’s confusing but if any doctor has told you differently, first check that you haven’t misunderstood them, but if they maintain that you have two different cancers then please run a mile from their care and find an expert.

It is true that especially on biopsy reports some doctors will write “has appearance of CLL / SLL”.  either to indicate the single combined condition (as SLL is considered the same disease as CLL) or to make it clear that on the basis of looking at the biopsy alone you can’t tell the difference. Unless the person writing the report knows what your lymphocyte count is in your blood they can’t specify which diagnosis is correct. The small cells they see under the microscope look exactly the same whether or not they are also growing in the blood. But that does NOT mean those expert doctors believe someone has two distinct blood cancers one called CLL and one called SLL.

For more than 20 years we have only used SLL to describe a variation of CLL that for some reason doesn’t grow in the blood. Any doctor who has left you with the idea that you have two separate cancers is either confused themselves or has not explained it very well. CLL is a crazy confused cancer that can’t decide if it wants to be a luekemia or a lymphoma so in most people it does both. Again I repeat, it is NOT two separate cancers.

On Patient Power, one of the top experts Dr Lamanna explains this as follows:

“They’re a disorder of the same B cell. So they’re under the microscope, exactly the same . . . But SLL patients are truly patients who have just lymph node involvement . . . you might actually have some bone marrow involvement.”

https://patientpower.info/chronic-lymphocytic-leukemia/treatments/whats-the-difference-between-cll-and-sll?fbclid=IwAR3hB2U87X3fYbBHAnSb0qHV9AJ5du9H004yDSq0UtMSysNfRyA6xxYaNEQ

Other quotes that explain this further:

“Small lymphocytic lymphoma  This type of lymphoma is the same disease as B-cell chronic lymphocytic leukemia (CLL) without a significant amount of disease in the blood.” 

https://www.cancer.net/cancer-types/lymphoma-non-hodgkin/subtypes

“To diagnose chronic lymphocytic leukemia (CLL), there needs to be ≥5000 monoclonal (genetically identical) B-lymphocytes (a type of white blood cell) in the blood for the duration of at least three months . . . Small lymphocytic lymphoma (SLL) and CLL are considered to be the same disease (at least since 1994).  The diagnosis of SLL requires the finding of enlarged lymph nodes and/or an enlarged spleen with less than 5000 B-lymphocytes in the blood. SLL cells show the identical immunophenotype (cell surface fingerprint) as CLL cells. The diagnosis of SLL should be confirmed by lymph node biopsy. CLL/SLL is considered both a lymphoma and leukemia.”

https://cllsociety.org/2016/03/diagnosis-chronic-lymphocytic-leukemia/?fbclid=IwAR3o6G69UWNNWJwxEkZ-odQbWenoEbriOjA3kOrwC3nkpZviXr1QPx3nbLs

“Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are viewed as similar entities by the WHO.¹ Histologically and immunophenotypically, CLL and SLL are identical, but patients with CLL, by definition, have more marked peripheral blood involvement.^2–4 An absolute lymphocyte count (ALC) of 5 × 10⁹/L has been used to distinguish SLL from CLL (with SLL defined by an ALC < 5 × 10⁹/L)”

https://ascopubs.org/doi/10.1200/JCO.2006.09.4508?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub++0pubmed&fbclid=IwAR3iBADR5_RTDC6JkIkOLoTA9l3Q8KvM-SuDm5s3fa_iHzhinyzjrp7RzKc&#_i36

“Chronic lymphocytic leukemia cells have a distinctive immunophenotype, and the disease has a characteristic pattern of histological infiltration in the lymph node and bone marrow . . . Some patients may present solely with lymphadenopathy, organomegaly, and presence of infiltrating monoclonal B cells with the same immunophenotype as CLL cells, but lacking peripheral blood lymphocytosis. This disease is called small lymphocytic lymphoma (SLL) and has been considered for almost 2 decades to be the tissue equivalent of CLL. Both CLL and SLL are currently considered different manifestations of the same entity by the fourth edition of the World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues” 

https://journals.lww.com/journalppo/Abstract/2012/09000/Small_Lymphocytic_Lymphoma_and_Chronic_Lymphocytic.4.aspx?fbclid=IwAR0nakljuKpBcTidJHpZPH1p_hx65MVRfSLFdl3prbvxYd9OS2isl8tiEQc

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