Globally, multiple myeloma affected 488,000 people and resulted in 101,100 deaths in 2015. This is up from 49,000 in 1990.

With high-dose therapy followed by autologous stem cell transplantation, the median survival has been estimated in 2003 to be approximately 4.5 years, compared to a median of approximately 3.5 years with "standard" therapy. Overall the 5-year survival rate is around 35%.

The International Staging System can help to predict survival, with a median survival (in 2005) of 62 months for stage 1 disease, 45 months for stage 2 disease, and 29 months for stage 3 disease.

The prognoses for patients with multiple myeloma, as those with other diseases, are not the same for everyone. The average age of onset is 70 years. Older patients are often experiencing other serious diseases, which affect survival. Younger patients might have much longer survival rates.

At the Mayo Clinic, MGUS transformed into multiple myeloma or similar lymphoproliferative disorder at the rate of about 1-2% a year, or 17%, 34%, and 39% at 10, 20, and 25 years, respectively, of follow-up—among surviving patients. However, because they were elderly, most patients with MGUS died of something else and did not go on to develop multiple myeloma. When this was taken into account, only 11.2% developed lymphoproliferative disorders.

Kyle studied the prevalence of myeloma in the population as a whole (not clinic patients) in Olmsted County, Minnesota. They found that the prevalence of MGUS was 3.2% in people above 50, with a slight male predominance (4.0% vs. 2.7%). Prevalence increased with age: of people over 70 up to 5.3% had MGUS, while in the over-85 age group the prevalence was 7.5%. In the majority of cases (63.5%), the paraprotein level was <1 g/dl, while only a very small group had levels over 2 g/dl. A study of monoclonal protein levels conducted in Ghana showed a prevalence of MGUS of approximately 5.9% in African men over the age of 50.

In 2009, prospective data demonstrated that all or almost all cases of multiple myeloma are preceded by MGUS. In addition to multiple myeloma, MGUS may also progress to Waldenström's macroglobulinemia, primary amyloidosis, B-cell lymphoma, or chronic lymphocytic leukemia.

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.

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).

Plasmacytomas are a rare form of cancer. SPB is the most common form of the disease and accounts for 3-5% of all plasma cell malignancies. The median age at diagnosis for all plasmacytomas is 55. Both SPB and extramedullary plasmacytoma are more prevalent in males; with a 2:1 male to female ratio for SPB and a 3:1 ratio for extramedullary plasmacytoma.

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 rarely associated with pregnancy, affecting only about 1 in 10,000 pregnant women. How it is handled depends primarily on the type of leukemia. Acute leukemias normally require prompt, aggressive treatment, despite significant risks of pregnancy loss and birth defects, especially if chemotherapy is given during the developmentally sensitive first trimester.

Pathologically, the lesion in MGUS is in fact very similar to that in multiple myeloma. There is a predominance of clonal plasma cells in the bone marrow with an abnormal immunophenotype (CD38+ CD56+ CD19−) mixed in with cells of a normal phenotype (CD38+ CD56− CD19+); in MGUS, on average more than 3% of the clonal plasma cells have the normal phenotype, whereas in multiple myeloma, less than 3% of the cells have the normal phenotype. What causes MGUS to transform into multiple myeloma is as yet unknown.

MBL has been found in less than 1% of asymptomatic adults under age 40, and in around 5% of adults older than 60. Exact numbers depend on the population studied and the sensitivity of the diagnostic technique.

Like CLL, it appears to be more common in males.

It is also a common finding among older adults with unexplained lymphocytosis.

Recent studies suggest that CLL is very often preceded by MBL,

and that MBL progresses to CLL requiring treatment at a rate of around 1-2% per year. Advancing age and high initial B cell count predispose to progression from MBL to CLL; however, only a small fraction of people with MBL die because of CLL.

Thus, MBL could be regarded as a premalignant condition from which some cases progress to CLL (much similar to the progression of some cases of monoclonal gammopathy of undetermined significance to multiple myeloma).

No treatment is required, but follow-up might be able to detect new diagnoses of CLL. However, this might lead to increased costs, repeated investigations, unnecessary anxiety about cancer and health insurance concerns, while there is no means to prevent progression to CLL.

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.

Secondary PCL (sPCL) is diagnosed in 1-4% of patients known to have had multiple myeloma for a median time of ~21 months. It is the terminal phase of these patients myeloma disease. sPCL patients typically are highly symptomatic due to extensive disease with malignant plasma cell infiltrations in, and failures of, not only the bone marrow but also other organs. They have failed or broke through one or more treatment regimens and therefore may also show some of the toxic effects of these treatments.

Little is yet known about the causes of MBL, but as it is a "forme fruste" of CLL the etiologies of these two conditions would be closely related. Genetic changes that can be found in CLL have also been found in MBL, and relatives of people with CLL have a much higher chance of having MBL (13% of first-degree relatives in one study).

One concern about MBL is related to blood transfusions. MBL was found in 0.14% of blood donors in one study. It is unknown whether blood transfusion can transmit MBL.

Novel approaches to the treatment of PTCL in the relapsed or refractory setting are under investigation. Pralatrexate is one compound currently under investigations for the treatment of PTCL.

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.

Paraproteinemia, also known as monoclonal gammopathy, is the presence of excessive amounts of paraprotein or single monoclonal gammaglobulin in the blood. It is usually due to an underlying immunoproliferative disorder or hematologic neoplasms, especially multiple myeloma. It is sometimes considered equivalent to plasma cell dyscrasia.

Causes of paraproteinemia include the following:

- Leukemias and lymphomas of various types, but usually B-cell Non-Hodgkin lymphomas with a plasma cell component.

- Myeloma

- Plasmacytoma

- Lymphoplasmacytic lymphoma

- Idiopathic (no discernible cause): some of these will be revealed as leukemias or lymphomas over the years.

- Monoclonal gammopathy of undetermined significance

- Primary AL amyloidosis (light chains only)

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.

Tumors of the hematopoietic and lymphoid tissues or haematopoietic and lymphoid malignancies are tumors that affect the blood, bone marrow, lymph, and lymphatic system. As those elements are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making myeloproliferation and lymphoproliferation (and thus the leukemias and the lymphomas) closely related and often overlapping problems.

While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of haematological malignancies.

Haematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "Haematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions (there are also surgical and radiation oncologists). Not all haematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.

Hematological malignancies may derive from either of the two major blood cell lineages: myeloid and lymphoid cell lines. The myeloid cell line normally produces granulocytes, erythrocytes, thrombocytes, macrophages and mast cells; the lymphoid cell line produces B, T, NK and plasma cells. Lymphomas, lymphocytic leukemias, and myeloma are from the lymphoid line, while acute and chronic myelogenous leukemia, myelodysplastic syndromes and myeloproliferative diseases are myeloid in origin.

A subgroup of them are more severe and are known as haematological malignancies (American spelling hematological malignancies) or blood cancer. They may also be referred to as liquid tumors.

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.

Plasmacytosis is a condition in which there is an unusually large proportion of plasma cells in tissues, exudates, or blood. Plasmacytosis may be divided into two types—cutaneous and systemic—both of which have identical skin findings.

Patients with plasmacytosis have been predominantly found to have lung infections (pneumonia, tuberculosis, abscess) whereas multiple myeloma is rarely found.

Myelophthisis can occur in the setting of chronic myeloproliferative disease (e.g. myelofibrosis), leukemia, lymphoma, and metastatic carcinoma or myeloma. It is common in people who have chronic idiopathic myelofibrosis. It has been linked to small-cell lung cancer, breast cancer or prostate cancer that metastasizes to the bone marrow.

Historically, the most common cause of displacement of healthy bone marrow was tuberculosis.

Currently, the most common cause is displacement of bone marrow by metastatic cancer (extramedullary hematopoiesis tends to be modest). Other causes include myeloproliferative disorders (especially late-stage or spent polycythemia vera), granulomatous diseases, and (lipid) storage diseases. Myelofibrosis can occur in all of these.

Factors that may contribute to decreased RBC production include a decreased quantity of functioning hematopoietic tissue, disordered metabolism related to the underlying disorder, and, in some cases, erythrophagocytosis.

Although not a malignant neoplasm like other cancers, MPNs are classified within the hematological neoplasms. There are four main myeloproliferative diseases, which can be further categorized by the presence of the Philadelphia chromosome:

In 2008, the World Health Organization listed these diagnoses as types of MPD:

- Chronic myelogenous leukemia (BCR-ABL1–positive)

- Chronic neutrophilic leukemia

- Polycythemia vera

- Primary myelofibrosis

- Essential thrombocythemia

- Chronic eosinophilic leukemia (not otherwise specified)

- Mastocytosis

The myeloproliferative neoplasms (MPNs), previously myeloproliferative diseases (MPDs), are a group of diseases of the bone marrow in which excess cells are produced. They are related to, and may evolve into, myelodysplastic syndrome and acute myeloid leukemia, although the myeloproliferative diseases on the whole have a much better prognosis than these conditions. The concept of myeloproliferative disease was first proposed in 1951 by the hematologist William Dameshek. In the most recent World Health Organization classification of hematologic malignancies, this group of diseases was renamed from "myeloproliferative diseases" to "myeloproliferative neoplasms". This reflects the underlying clonal genetic changes that are a salient feature of this group of disease.

The increased numbers of blood cells may not cause any symptoms, but a number of medical problems or symptoms may occur. The risk of thrombosis is increased in some types of MPN.

Some cases of myelophthisis are thought to be related to the release of cytokines that simulate fibroblastic proliferation and fibrosis in the marrow.