Less than 1% of all lymphomas are splenic marginal zone lymphomas and it is postulated that SMZL may represent a large fraction of unclassifiable CD5- chronic lymphocytic leukemias. The typical patient is over the age of 50, and gender preference has been described.

T-PLL is an extremely rare aggressive disease, and patients are not expected to live normal lifespans. Before the recent introduction of better treatments, such as alemtuzumab, the median survival time was 7.5 months after diagnosis. More recently, some patients have survived five years and more, although the median survival is still low.

Of all cancers involving the lymphocytes, 1% of cases are WM.

WM is a rare disorder, with fewer than 1,500 cases occurring in the United States annually. The median age of onset of WM is between 60 and 65 years, with some cases occurring in late teens.

Taken together, haematological malignancies account for 9.5% of new cancer diagnoses in the United States and 30,000 patients in the UK are diagnosed each year. Within this category, lymphomas are more common than leukemias.

The 5 year survival has been noted as 89% in at least one study from France of 201 patients with T-LGL leukemia.

About four men are diagnosed with this disease for every three women. Despite its overall rarity, it is also the most common type of mature T cell leukemia.

Current medical treatments result in survival of some longer than 10 years; in part this is because better diagnostic testing means early diagnosis and treatments. Older diagnosis and treatments resulted in published reports of median survival of approximately 5 years from time of diagnosis. Currently, median survival is 6.5 years. In rare instances, WM progresses to multiple myeloma.

The International Prognostic Scoring System for Waldenström’s Macroglobulinemia (IPSSWM) is a predictive model to characterise long-term outcomes. According to the model, factors predicting reduced survival are:

- Age > 65 years

- Hemoglobin ≤ 11.5 g/dL

- Platelet count ≤ 100×10/L

- B2-microglobulin > 3 mg/L

- Serum monoclonal protein concentration > 70 g/L

The risk categories are:

- Low: ≤ 1 adverse variable except age

- Intermediate: 2 adverse characteristics or age > 65 years

- High: > 2 adverse characteristics

Five-year survival rates for these categories are 87%, 68% and 36%, respectively. The corresponding median survival rates are 12, 8, and 3.5 years.

The IPSSWM has been shown to be reliable. It is also applicable to patients on a rituximab-based treatment regimen. An additional predictive factor is elevated serum lactate dehydrogenase (LDH).

The exact cause of most cases of childhood leukemia is not known. Most children with leukemia do not have any known risk factors. The immune system plays an important role in protecting the body's immune system. An alteration or defect in the immune system may increase the risk for developing cancer. The immune system can be damaged by different factors, such as exposure to different viruses, environmental factors, chemical factors and other various infections.

There also appears to be some evidence linking childhood leukemia to x-ray exposure. In a 2010 study by the University of California, Berkeley’s School of Public Health, researchers found that children with acute lymphoid leukemia (ALL) had almost twice the chance of having been exposed to three or more X-rays compared with children who did not have leukemia.

This disease is rare, with fewer than 1 in 10,000 people being diagnosed with HCL during their lives. Men are four to five times more likely to develop hairy cell leukemia than women. In the United States, the annual incidence is approximately 3 cases per 1,000,000 men each year, and 0.6 cases per 1,000,000 women each year.

Most patients are white males over the age of 50, although it has been diagnosed in at least one teenager. It is less common in people of African and Asian descent compared to people of European descent.

It does not appear to be hereditary, although occasional familial cases that suggest a predisposition have been reported, usually showing a common Human Leukocyte Antigen (HLA) type.

T-LGLL is a rare form of leukemia, comprising 2-3% of all cases of chronic lymphoproliferative disorders.

Despite decade-long remissions and years of living very normal lives after treatment, hairy cell leukemia is officially considered an incurable disease. While survivors of solid tumors are commonly declared to be permanently cured after two, three, or five years, people who have hairy cell leukemia are never considered 'cured'. Relapses of HCL have happened even after more than twenty years of continuous remission. Patients will require lifelong monitoring and should be aware that the disease can recur even after decades of good health.

People in remission need regular follow-up examinations after their treatment is over. Most physicians insist on seeing patients at least once a year for the rest of the patient's life, and getting blood counts about twice a year. Regular follow-up care ensures that patients are carefully monitored, any changes in health are discussed, and new or recurrent cancer can be detected and treated as soon as possible. Between regularly scheduled appointments, people who have hairy cell leukemia should report any health problems, especially viral or bacterial infections, as soon as they appear.

HCL patients are also at a slightly higher than average risk for developing a second kind of cancer, such as colon cancer or lung cancer, at some point during their lives (including before their HCL diagnosis). This appears to relate best to the number of hairy cells, and not to different forms of treatment. On average, patients might reasonably expect to have as much as double the risk of developing another cancer, with a peak about two years after HCL diagnosis and falling steadily after that, assuming that the HCL was successfully treated. Aggressive surveillance and prevention efforts are generally warranted, although the lifetime odds of developing a second cancer after HCL diagnosis are still less than 50%.

There is also a higher risk of developing an autoimmune disease. Autoimmune diseases may also go into remission after treatment of HCL.

This is a rare disease, with less than 100 cases reported. Of these cases, an equal male:female ratio was observed,

with cases typically seen in older adults.

CLL is primarily a disease of older adults, with a median age of 70 years at the time of diagnosis. Though less common, CLL sometimes affects people between 30 and 39 years of age. The incidence of CLL increases very quickly with increasing age.

In the United States during 2014, about 15,720 new cases are expected to be diagnosed, and 4,600 patients are expected to die from CLL. Because of the prolonged survival, which was typically about 10 years in past decades, but which can extend to a normal life expectancy, the prevalence (number of people living with the disease) is much higher than the incidence (new diagnoses). CLL is the most common type of leukemia in the UK, accounting for 38% of all leukemia cases. Approximately 3,200 people were diagnosed with the disease in 2011.

In Western populations, subclinical "disease" can be identified in 3.5% of normal adults, and in up to 8% of individuals over the age of 70. That is, small clones of B cells with the characteristic CLL phenotype can be identified in many healthy elderly persons. The clinical significance of these cells is unknown.

In contrast, CLL is rare in Asian countries, such as Japan, China, and Korea, accounting for less than 10% of all leukemias in those regions. A low incidence is seen in Japanese immigrants to the US, and in African and Asian immigrants to Israel.

Of all cancers involving the same class of blood cell, 7% of cases are CLL/SLL.

Rates of CLL are somewhat elevated in people exposed to certain chemicals. Under U.S. Department of Veterans' Affairs regulations, Vietnam veterans who served in-country or in the inland waterways of Vietnam and who later develop CLL are presumed to have contracted it from exposure to Agent Orange and may be entitled to compensation.

Three-quarters of patients survive five or more years; more than half of patients with SMZL survive more than a decade after diagnosis.

Patients who have a hemoglobin level of less than 12 g/dL, a lactate dehydrogenase level higher than normal, and/or a blood serum albumin levels of less than 3.5 g/dL are likely to have more an aggressive disease course and a shorter survival. However, even high-risk patients have even odds of living for five years after diagnosis.

Some genetic mutations, such as mutations in "NOTCH2", are also correlated with shorter survival.

Historically, hematological malignancies have been most commonly divided by whether the malignancy is mainly located in the blood (leukemia) or in lymph nodes (lymphomas).

However, the influential WHO Classification (published in 2001) placed a greater emphasis on cell lineage.

Relative proportions of hematological malignancies in the United States

The prognosis is generally poor. The "RS score" (Richter syndrome score), which is an estimate of the patient's prognosis, is based on the patient's performance status, LDH, platelet count, the size of the lymphoma tumors, and the number of prior therapies already received. Overall, the median survival is between five and eight months. Untreated, RS is invariably fatal.

The Hodgkin's lymphoma variant of Richter's carries a better prognosis than the predominant diffuse large B-cell lymphoma type, but a worse prognosis than a "de novo" case of Hodgkin's.

In the United States, about 500 patients are diagnosed with Richter's transformation each year.

SCTC exhibits a highly aggressive phenotype, thus prognosis of that malignancy is extremely poor. The overall survival is less than 1 year in most of cases.

Prognosis depends on the subtype. Some subtypes have a median survival of 6–8 years, while others have a median survival of 22 years (which is a normal lifespan for older patients). Telomere length has been suggested to be a valuable prognostic indicator of survival.

The majority (90%) of cases have not had detectable cytogenetic abnormalities. Most importantly, the Philadelphia chromosome and other BCR/ABL fusion genes are not detected.

A B-cell leukemia is any of several types of lymphoid leukemia which affect B cells.

Types include (with ICD-O code):

- 9823/3 - B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma

- 9826/3 - Acute lymphoblastic leukemia, mature B-cell type

- 9833/3 - B-cell prolymphocytic leukemia

- 9835/3-9836/3 - Precursor B lymphoblastic leukemia

- 9940/3 - Hairy cell leukemia

Plasma cell leukemia (PCL) is a plasma cell dyscrasia, i.e. a disease involving the malignant degeneration of a subtype of white blood cells called plasma cells. It is the terminal stage and most aggressive form of these dyscrasias, constituting 2% to 4% of all cases of plasma cell malignancies. PCL may present as primary plasma cell leukemia, i.e. in patients without prior history of a plasma cell dyscrasia or as secondary plasma cell dyscrasia, i.e. in patients previously diagnosed with a history of its predecessor dyscrasia, multiple myeloma. The two forms of PCL appear to be at least partially distinct from each other. In all cases, however, PCL is an extremely serious, life-threatening, and therapeutically challenging disease.

Most cases of SPB progress to multiple myeloma within 2–4 years of diagnosis, but the overall median survival for SPB is 7–12 years. 30–50% of extramedullary plasmacytoma cases progress to multiple myeloma with a median time of 1.5–2.5 years. 15–45% of SPB and 50–65% of extramedullary plasmacytoma are disease free after 10 years.

Leukemia is usually described either as "acute", which grows quickly, or "chronic", which grows slowly. One main type of acute leukemia is acute lymphocytic leukemia (ALL), which accounts for about 3 out of 4 cases of leukemia in children. ALL is a form of leukemia that affects the lymphocytes, a type of white blood cells which fights infection. When a patient has ALL, the bone marrow makes too many immature white blood cells and they do not mature correctly. Therefore, the white blood cells over-produce, crowding the other blood cells. The white blood cells also do not work correctly to fight infection.

Another type of acute leukemia is acute myelogenous leukemia (AML). AML is cancer of the blood in which too many myeloblasts, immature white blood cells, are produced in the bone marrow. The marrow continues to produce abnormal cells that crowd the other blood cells and do not work properly to fight infection. Almost all childhood leukemia is acute.

Chronic leukemias are more common in adults than in children, and although they tend to grow more slowly than acute leukemias, they are harder to treat. These chronic leukemias are divided into two types: chronic myelogenous leukemia (CML) and chronic lymphocytic leukemia (CLL). CML is rare in children, but does occur and is treatable in children the same as in adults. CML patients have too many immature white blood cells being produced, and the cells crowd the other healthy blood cells.

A specific chromosome rearrangement is also found in patients with CML, among the 46 chromosomes in human cells. Part of chromosome nine breaks off and attaches itself to chromosome 22, meaning there is an exchange of genetic material between chromosomes 9 and 22. The rearrangement of the chromosomes changes the positions and functions of certain genes, which causes uncontrolled cell growth.

CLL is another form of chronic leukemia, but is extremely rare in children. Juvenile myelomonocytic leukemia (JMML) is a form of leukemia that is neither chronic nor acute and occurs most often in children under the age of four. JMML begins from myeloid cells, but is not as fast-growing as AML or as slow as CML.

ANKL is treated similarly to most B-cell lymphomas. Anthracycline-containing chemotherapy regimens are commonly offered as the initial therapy. Some patients may receive a stem cell transplant.

Most patients will die 2 years after diagnosis.