When you hear the word "cancer", your first thought is probably related to a lump of some sort forming inside the body. However, unlike these solid masses, cancer can also develop due to the uncontrolled division of the cells inside your blood, bone marrow, or lymphatic system.
These major types of cancers actually involve a large number of different subtypes which, other than the fact they all originate from the blood cells and may lead to somewhat similar symptoms, can be strikingly different, especially when it comes to prognosis and treatment of these patients.
For example, even though both leukemia and lymphoma affect the white blood cells, leukemia is characterized by a large number of abnormal cells of different origin in the peripheral blood, and typically starts in the bone marrow, whereas lymphomas usually start in the lymph nodes, and affects only specific types of blood cells, called lymphocytes.
Both lymphoma and leukemia tend to interfere with the normal production of white blood cells, which presents an important way the blood fights off infections. Unfortunately, since these diseases usually don’t form any tumorous masses, they are extremely hard to diagnose.
As an exception to this rule, lymphoma can, however, present as a tumorous mass. To make matters worse, blood cancer tends to produce mostly non-specific symptoms, such as fatigue, fevers, recurrent infections, weight loss, or sweating, none of which may seem like a big deal for an average patient, which may manifest in late diagnosis and, therefore, worse prognosis.
What do you need to know about the most common forms of blood cancer?
In order to better understand these diseases, we need to know what makes each of them unique. There are four most common types of leukemia, two of which form rapidly. They are therefore called acute leukemia forms, whereas the remaining slowly-formed type is dubbed chronic leukemia.
Depending on the type of blood cells affected, acute and chronic leukemia can further be classified as myelogenous (related to the blood-forming tissue cells), or lymphocytic (affecting the lymphocytes while in the bone marrow).
So, the basic classification of leukemia would involve:
- Acute myelogenous leukemia (AML) – the most common type of acute leukemia in adults.
- Chronic myelogenous leukemia (CML) – fairly rare (less than 10 percent of all leukemias).
- Acute lymphocytic leukemia (ALL) – the most common type of leukemia in people of a young age.
- Chronic lymphocytic leukemia (CLL) – the most common type of chronic leukemia in adults (one third of all leukemias).
Lymphomas, on the other hand, originate in lymphatic tissue, which, other than lymphocytes, may also include the lymph nodes, spleen, thymus, and even the bone marrow, since the lymph vessels drain directly into the bloodstream. Lymphomas can also affect the tonsils, respiratory tract, and mucus tissues, like in the digestive tract.
Although there are more than 30 different forms of lymphoma, they are all classified as:
- Hodgkin Lymphoma – characterized by the existence of a specific type of cell.
- Non-Hodgkin Lymphoma – an umbrella term which involves all other types of this disease.
How does blood cancer affect other organs?
Since these cancers originate in the blood and the lymphatic system, they are capable of traveling very far to the different parts of the body, where they accumulate, thereby disrupting the function of the cells normally found there.
Similar to solid cancers, leukemia may build up inside the lymph nodes, causing them to become larger in size. Enlarged lymph nodes usually mean that the body is fighting off an infection, and they can be diagnosed even in people dealing with a common cold. On the other hand, enlarged lymph nodes can be an important detail when it comes to diagnosing leukemia in its relatively early stages.
Therefore, doctors analyze the properties of these lymph nodes, such as their size, shape, how long have they been enlarged, and whether they hurt or not. Of course, this is just one part of the diagnostic process, which would not be complete without a blood count, or bone marrow and lymph node biopsy. Other than the superficial ones, enlarged lymph nodes may commonly appear in the thorax, and can be effectively identified during a CT scan.
Enlarged lymph nodes are also found in lymphoma patients, but the main difference is that leukemia spreads to lymph nodes, whereas lymphoma originates in them. In a similar fashion, the spleen can also be enlarged due to the buildup of abnormal leukemia cells. However, since the spleen is technically a part of the lymphatic system, lymphomas are more common in this organ than leukemia. Additionally, since almost every organ has some amount of lymphatic tissue, lymphomas can virtually appear in every one of them.
The central nervous system may also be affected by some types of leukemia. Changes can be found both in the brain itself, as well as the cerebrospinal fluid surrounding it. In these patients, this kind of cancer may manifest in many different forms, including vertigo, nausea, visual disturbances, nerve palsy, and even seizures and coma. Besides analyzing cerebrospinal fluid in order to find abnormal cells, MRI is also used in detecting changes in the brain caused by metastatic leukemia.
Another somewhat common place where leukemia can spread to are the testicles, which are in these cases enlarged, but usually painless. In order to further diagnose these manifestations, a testicular ultrasound should be performed. Since the changes are usually non-specific, these results are worthless without additional laboratory tests and clinical history.
When it comes to the skeletal system, since leukemia originates in the bone marrow, it most frequently causes bone density to decrease (osteopenia), which can even be detected on plain X-rays. Other frequent complications may include the irritation of the membrane on the outer surface of the bones, called the periosteum. In case that vertebral bodies in the spine are affected, it may cause them to fracture and collapse. The changes in the skeletal system are best diagnosed with the help of an MRI scan.
Because of their striking similarities, it is necessary to fully understand every type of blood cancer and their characteristics, such as the most likely place they originated, or where they can spread, as well as the symptoms they might produce.
It’s also important to know that a large number of these changes can also be caused by medications or radiation used in therapy of these diseases. Only after that, with the help of different diagnostic methods, such as complete blood count, medical imaging, and of course, spinal tap, we could put these pieces of the puzzle together in order to create a successful therapy plan for each individual patient.