What Is a Hematologist-Pathologist?

Pathology means disease or a deviation from normal and hematology is the study of blood. Hematology-Pathology is the field of medicine that is primarily focused on diagnosing and assessing diseases of the blood which have a very wide spectrum ranging from anemia and bleeding disorders to cancers such as leukemia and lymphoma.


Hematology-Pathology or hematopathology for short is one of the subspecialties of pathology. There are 11 pathology subspecialties in total:

  • Blood Banking/ Transfusion Medicine
  • Clinical Informatics
  • Hematopathology
  • Cytopathology
  • Dermatopathology
  • Neuropathology
  • Pathology – Chemical
  • Pathology – Forensic
  • Pathology – Medical Microbiology
  • Pathology – Pediatric
  • Pathology – Molecular Genetic

Diseases encountered by hematopathologists

Hematopathologists mainly diagnose through lab tests. These include complete blood picture, flow cytometry, molecular diagnostics, cytogenetics, hemoglobin electrophoresis, blood films, and more. Don’t get it twisted by thinking that all they need is a test and that their diagnosis is based solely on a piece of paper. They need to know all the relevant information about the patient such as their age, gender, occupation, and any risk factors they might have for a particular disease. It also helps to know if they’re on any drugs as certain drugs can result in altered test results which might result in a misdiagnosis.

Anemia is one of the commonest diseases in the world. It’s a condition where the amount of hemoglobin in the body is decreased rendering the oxygen delivery to tissue insufficient. That’s because it’s a relatively benign condition up to a certain point meaning that unless you’re severely anemic then your life isn’t in danger (unless you perform activities that require a lot of physical effort). People might also ignore the symptoms and attribute them to a lack of sleep or having too much to do and not enough time to rest. If the anemia becomes severe enough in might be fatal as it causes anemic heart failure where the heart has to work extra hard because the body isn’t getting enough oxygen.

The most common cause of anemia worldwide is iron deficiency anemia as iron is essential for the production of red blood cells. It’s diagnosed by a complete blood count (CBC) that shows low hemoglobin level as well as smaller than normal red blood cell dimensions. Other causes of small RBC dimensions are thalassemia. In thalassemia there’s a problem with the manufacturing of RBCs and to differentiate between both conditions we rely on a test called hemoglobin electrophoresis as well as the total iron concentration in the body.

Other popular causes of anemia are vitamin B12 and folic acid deficiencies. Vegetarians who don’t incorporate enough vitamin B12 in their diets may suffer from this. Folic acid is also very important for women in the childbearing period as its deficiency during pregnancy can result in neurological anomalies in the fetus. That’s why women looking to conceive are advised to start taking folic acid 3 months before they start trying to get pregnant and for the first 3 months of pregnancy. Pregnant women are also given iron supplements as there’s hemodilution during pregnancy because the plasma volume in pregnant women increases making the RBC count and hemoglobin lower in comparison even if they were originally normal.

Next we have bleeding and clotting disorders. What’s the difference? Well when we talk about bleeding disorders we’re mainly talking about platelets while with clotting disorders our main focus are the clotting factors. When a blood vessel is injured the platelets are what stop the bleeding then clotting factors arrive and seal the injury in order to seal off the damaged part. Bleeding disorders can be due to thrombocytopenia or thrombasthenia.

Thrombocytopenia is defined as a low number of platelets. In contrast, thrombasthenia has a normal number of platelets but these platelets aren’t functioning as they should. It’s not enough to have enough platelets, but they also need to be functioning properly in order for bleeding to stop. Causes of thrombocytopenia are variable. The problem could be in manufacturing as the bone marrow isn’t producing enough platelets. It can also be due to increased destruction. This might be idiopathic without an apparent cause or due to mechanical microangiopathy. One of the most common things that result in platelet destruction is splenomegaly. The spleen is the organ responsible for destroying old blood products and this is normal in all of us, but if it increases in size and goes crazy it can start breaking down everything resulting in thrombocytopenia.

Thrombasthenia is more complicated as it has to do with receptors present in platelets which affect their function. It can also be due to problems with proteins present inside the platelets. Examples of diseases causing thrombasthenia are Glanzmann’s disease and Bernard Soulier. Thrombocytopenia is definitely more common and has more causes than thrombasthenia.

Next we have clotting disorders. These often present with internal bleeding such as in the joints and gastrointestinal tract. Bleeding disorders usually present with external bleeding like bleeding from the nose or gums. We can measure clotting factors just like we can measure platelets. There are two main investigations to assess clotting factors. Clotting is divided into intrinsic and extrinsic pathways according to the site or extent of injury. In order to assess the intrinsic pathway we use partial thromboplastin time. When it comes to the extrinsic pathway we use prothrombin time or INR. We can also measure individual factors in the blood in order to be more specific.

The commonest clotting disorder and one of the most well known diseases in the world is hemophilia A which is due to a deficiency in the production of clotting factor 8. There’s also hemophilia B which is much milder than hemophilia A and is due to a deficiency in the production of clotting factor 9. Both of these are x-linked recessive diseases meaning they almost exclusively affect males. They can present with internal bleeding which may affect the joints and even the brain resulting in very serious complications. Clotting factor disorders can be treated in a variety of ways which can include giving the patient the deficient clotting factor via transfusion. Luckily we don’t need to transfuse whole blood with all of its elements and now we can only administer the absent clotting factor. This treatment has to be repeated as clotting factors only live for a few days and can be quite expensive for people without insurance and in developing countries.

Additional tests can be used to tell the difference between clotting and bleeding disorders such as bleeding and clotting times. To test a person’s bleeding time a doctor will create a small cut in their skin and see how long it takes for the bleeding to stop. An increase in the time means there’s a problem with the platelets. Clotting time tests the time it takes a person’s blood to form a blood clot. Again, an increase in clotting time means a problem with the clotting or coagulation factors.

Hematological cancers are a very large part of any hematopathologists job. These cancers can often give clinical pictures that aren’t specific or well defined and the diagnosis always comes down to clinical pathology. The cancers we’re talking about here are leukemia and lymphoma.

There are so many variants of leukemia and that’s all definitely beyond our scope here. Let’s just say that there are acute and chronic leukemias and that acute leukemias are definitely more dangerous and can be more lethal more rapidly than chronic kinds. In order to diagnose leukemia a bone marrow biopsy is needed which is usually taken from the pelvic bone. A hematopathologist will then be able to identify if leukemia is present and if it is they’ll be able to identify the subtype.

Lymphoma is cancer that affects the lymphocytes which are cells in the blood responsible for defense against viruses and cancer (yes, cancer). The two main subtypes of lymphoma are Hodgkin’s and Non-Hodgkin’s lymphoma. A lymph node biopsy is viewed under the microscope and the hematopathologist will be able to diagnose the condition and the subtype. Both lymphoma and leukemia can give mixed clinical pictures and must be suspected in patients who have low immune systems, fatigue, and a fever that’s not explained by anything else. The diagnosis will rely almost completely on the hematopathologist.

Finally we have immunodeficiencies. So many things can cause immunodeficiency in an individual. These can range from hereditary diseases to HIV to cancer. Some of the hereditary forms are severe combined immunodeficiency, combined variable immunodeficiency, and immunoglobulin deficiency. These tests are diagnosed using flowcytometry and certain markers present on the cells. When we count a certain type of cell in the blood, for example T-cells, and we find it to be deficient this can help us identify the kind of deficiency. Immune cells also have specific cell markers. These can be used by doctors who specialize in hematology-pathology in order to specifically identify the kind of deficient cell. It’s not just enough to identify a T-cell deficiency for example as there are several kinds of T-cells and each has a certain role.

Cancers such as leukemia and lymphoma can affect the immune system or might be due to immunodeficiency. We mentioned that a healthy immune system helps protect us from cancer. So an ineffective immune system will result in the survival of these aberrant cancer cells. The cancers themselves can cause immunodeficiency as well. Leukemia which starts in the bone marrow causes rapid synthesis of cells in the immune system. You’re thinking this should mean additional immune cells and therefore a healthier person, right? Wrong. When cells multiply rapidly before they’re mature enough then they don’t function very well.

These are the majority of diseases that hematopathologists encounter. All of them need particular investigations and lab tests in order to be diagnosed and most of these tests fall under the jurisdiction of pathologists. Again, don’t think this means that all they need are machines and lab results. At the end of the day doctors deal with patients not lab results and pieces of paper. They need to know as much details as possible about the patient in order to come up with a definitive diagnosis or else these tests are just numbers on a paper.

Importance of hematopathology

It’s important to be able to identify the underlying disease causing the bleeding, anemia, or immunodeficiency. All of these conditions can be fatal if left untreated. The treatment will depend on what’s causing each of them. If a patient is bleeding into his or her joints or internal organs then it’s important to diagnose the clotting deficiency that they have and not just diagnose that there’s a clotting disorder in general. The same goes for anemia. Treating anemia due to iron deficiency means giving iron, but treating anemia caused by thalassemia for example will need actually getting rid of excess iron that the patient has.

The same applies to immunodeficiency as some forms are congenital while some are acquired. Knowing the defect in the immune system will help provide a more targeted therapy. Knowing the exact etiology for a disease also decides the prognosis. Not all immunodeficiencies or bleeding disorders for example are as severe as others. The only way an accurate diagnosis can be reached is through various tests and here is where hematopathologists come in.

History of hematopathology

In September of 1981 the Society of Hematopathology was founded as a companion society of the International Academy of Pathology in the United States and Canada. The International Academy of Pathology was later incorporated in the United States and Canadian Academy of Pathology. This was done in 1986. The Society for Hematopathology was cofounded by two physicians: Dr. Costan W. Berard and Dr. Ronald F. Dorfman. Dr. Berard was the first president of the society and his term lasted for 2 years from 1982 to 1984. The following two years were Dr. Dorfman’s who was president from the year 1984 to the year 1986. The very first official meeting for the society was in 1982, specifically the 28th of February, in Boston, Massachusetts where they dealt with the topic of T-cell lymphomas.

Tennessee was the Society of Hematopathology’s home as Dr. Costan W. Berard, the society’s first president, was working at St. Jude Medical Center in Memphis as the Chairman of Pathology. Dr. Berard’s wife, Sue Berard, handled the society’s administrative duties. She was the society’s executive secretary. The society’s newsletters as well as annual dues notices were sent from her home until the year 2,000. This was under 20 years ago.

The society’s mission statement was and still is clear. It’s to stimulate interest, investigation, and to exchange and disseminate knowledge regarding all that concerns the hematopoietic and lymphoreticular systems focusing on their clinical, morphological, and functional aspects. The hematopoietic system includes the red blood cells, white blood cells, and platelets which are all produced in the bone marrow. The lymphoreticular system includes the lymph nodes, spleen, and liver. Membership to the society is now open on a worldwide basis, but obviously during its start it was relatively restricted to the United States and Canada as it was still a work in progress.

Hematology-Pathology started to blossom in the 1970s as a lot of inventions and discoveries were being made in the field. This was the time of the invention of chemotherapy and its use to treat different kinds of cancer. Diseases such as leukemia and lymphoma are two particular types of cancer that can be treated by chemotherapy alone or occasionally chemotherapy in addition to radiotherapy. When there’s better treatment for a disease more focus is present on the diagnosis of that disease. It’s like with screening programs. Think of it this way, if you can treat something completely then you would want to diagnose it as soon as possible and as often as possible. If you can’t treat something at all then whether or not you diagnose it early doesn’t make much of a difference.

So the discovery of chemotherapy resulted in greater focus on the diagnosis of leukemia and lymphoma. There was also an increased interest in classifying lymphoma which is evident by the Kiel classification by Dr. Karl Lennert and the Lukes and Collins classification. Both of these classifications were published in 1974. More classifications systems started to appear until we had 6 of them. The people who made these systems met in Virginia in 1975 in order to settle their differences and come up with a single classification system but their meeting wasn’t fruitful. Ultimately a final classification was published in 1982.

Encouraged by all that was happening in the United States and Canada, the first Lymphoma Club meeting in Europe was held in Germany in the year 1974. The meeting was organized by Karl Lennert (who we previously mentioned created his own lymphoma classification system). The purpose of the meeting was to exchange ideas in order to achieve the maximum benefit from Dr. Kiel’s classification system when it comes to diagnosis and research. Not many American physicians made the trip to Europe for that meeting but they certainly felt its impact and decided to have a meeting for their own. Now there’s an annual Symposia of the Society of Hematopathology in the United States which has the same purpose of the European Lymphoma Club. The American symposia also hosts experts from other fields related to hematopathology such as molecular biologists and clinical oncologists in order to gain from their knowledge and expertise.

You can see it like to-and-fro between the American and European hematopathologists. One of them would do something and the others would try to imitate and add to it. As the Society of Hematopathologists in the United States became more successful, those who participated in the European Lymphoma Club decided to expand and add more authority and activities to their program and formed the European Association for Hematopathology. Their first meeting was both a meeting and a workshop. It was held in Geneva in the year 1988 and the topic of the workshop was extranidal lymphomas (lymphomas present outside lymph nodes).

In 1991 the American hematopathology society had its first workshop as well which was organized by Peter Banks and held in Texas. The workshop was on the relationship between Hodgkin and Non-Hodgkin lymphomas. This to-and-fro between both American and European societies finally came to an end when they decided to work together in order to discuss the WHO’s proposed classification in 1997. This happened in Florida. Since then multiple conjoint workshops have been held between both societies with the first being in Barcelona in 1999. As the years have progressed there has been more cooperation and work between both the American and European societies.

Future of hematopathology

Hematology-Pathology is still a relatively young field considering things started to look up for it in the 1970s with the discovery of chemotherapy. With each passing day newer methods of diagnosis of hematological diseases are being discovered which improve the accuracy of diagnosis and potential for treatment. Older methods of investigation are becoming obsolete as we progress towards faster and more accurate methods of diagnosis.   

How to become a hematopathologist

In order to become a pathologist you have to have a college degree and then enter med school for 4 years. After 4 years of medical school you then apply for a pathology residency which is about 3-4 years and then you apply for a fellowship in Hematology-Pathology.

Hematopathologists usually work fixed hours every day so you don’t need to worry about getting called in at night like surgeons or obstetricians for example. So if you prefer a certain lifestyle that revolves around fixed schedules and not many variations this might be a good medical specialty for you. If you would rather have a specialty with more emergencies, late night calls, and patient interaction then you should consider something like surgery or cardiology.










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