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

For the analysis of a suspected "hematological malignancy", a complete blood count and blood film are essential, as malignant cells can show in characteristic ways on light microscopy. When there is lymphadenopathy, a biopsy from a lymph node is generally undertaken surgically. In general, a bone marrow biopsy is part of the "work up" for the analysis of these diseases. All specimens are examined microscopically to determine the nature of the malignancy. A number of these diseases can now be classified by cytogenetics (AML, CML) or immunophenotyping (lymphoma, myeloma, CLL) of the malignant cells.

Flow cytometry is a diagnostic tool in order to count/visualize the amount of lymphatic cells in the body. T cells, B cells and NK cells are nearly impossible to distinguish under a microscope, therefore one must use a flow cytometer to distinguish them.

The International Myeloma Working Group has defined the diagnostic criteria for plasma cell leukemia as the presence in blood of >2x10 plasma cells per liter or, alternatively, >20% of nucleated blood cells being plasma cells. More recently, the Group has suggested that values of 0.5x10 or 5%, respectively, may be more appropriate from a therapeutic viewpoint and therefore should be studied as a definitive criterion for the disease. A recent study supported this suggestion in finding that multiple myeloma patients with >5% circulating plasma cells had a prognosis much worse than that for multiple myeloma and similar to that for plasma cell leukemia. Flow cytometry immunophenotyping of blood cells to detect clonal phenotypes of plasma cells seen in multiple myeloma (e.g. the CD138, CD38, CD19, CD45 phenotype) may be a more sensitive method to enumerate circulating clonal plasma cells and diagnose plasma cell leukemia.

Because the cause is unknown, no effective preventive measures can be taken.

Because the disease is rare, routine screening is not cost-effective.

The diagnosis of HCL may be suggested by abnormal results on a complete blood count (CBC), but additional testing is necessary to confirm the diagnosis. A CBC normally shows low counts for white blood cells, red blood cells, and platelets in HCL patients. However, if large numbers of hairy cells are in the blood stream, then normal or even high lymphocyte counts may be found.

On physical exam, 80–90% of patients have an enlarged spleen, which can be massive. This is less likely among patients who are diagnosed at an early stage. Peripheral lymphadenopathy (enlarged lymph nodes) is uncommon (less than 5% of patients), but abdominal lymphadenopathy is a relatively common finding on computed tomography (CT) scans.

The most important lab finding is the presence of hairy cells in the bloodstream. Hairy cells are abnormal white blood cells with hair-like projections of cytoplasm; they can be seen by examining a blood smear or bone marrow biopsy specimen. The blood film examination is done by staining the blood cells with Wright's stain and looking at them under a microscope. Hairy cells are visible in this test in about 85% of cases.

Most patients require a bone marrow biopsy for final diagnosis. The bone marrow biopsy is used both to confirm the presence of HCL and also the absence of any additional diseases, such as Splenic marginal zone lymphoma or B-cell prolymphocytic leukemia. The diagnosis can be confirmed by viewing the cells with a special stain known as TRAP (tartrate resistant acid phosphatase). More recently, DB44 testing assures more accurate results.

It is also possible to definitively diagnose hairy cell leukemia through flow cytometry on blood or bone marrow. The hairy cells are larger than normal and positive for CD19, CD20, CD22, CD11c, CD25, CD103, and FMC7. (CD103, CD22, and CD11c are strongly expressed.)

Hairy cell leukemia-variant (HCL-V), which shares some characteristics with B cell prolymphocytic leukemia (B-PLL), does not show CD25 (also called the Interleukin-2 receptor, alpha). As this is relatively new and expensive technology, its adoption by physicians is not uniform, despite the advantages of comfort, simplicity, and safety for the patient when compared to a bone marrow biopsy. The presence of additional lymphoproliferative diseases is easily checked during a flow cytometry test, where they characteristically show different results.

The differential diagnoses include: several kinds of anemia, including myelophthisis and aplastic anemia, and most kinds of blood neoplasms, including hypoplastic myelodysplastic syndrome, atypical chronic lymphocytic leukemia, B-cell prolymphocytic leukemia, or idiopathic myelofibrosis.

Leukemia is diagnosed in a variety of ways. Some diagnostic procedures include:

- A bone-marrow aspiration and biopsy; marrow may be removed by aspiration or a needle biopsy.

- A complete blood count, which is a measurement of size, number, and maturity of different blood cells in blood.

- Blood tests may include blood chemistry, evaluation of liver and kidney functions, and genetic studies.

- A lymph-node biopsy; lymph node tissue is surgically removed to examine under a microscope, to look for cancerous cells.

- A spinal tap: a special needle is placed into the lower back into the spinal canal, which is the area around the spinal cord. Cerebral spinal fluid is fluid that bathes the child's brain and spinal cord. A small amount of cerebral spinal fluid is sent for testing to determine if leukemia cells are present.

Ultrasound-guided FNAC should be performed for verification of SCTC.

Immunohistochemistry is performed as additional test. The strong positive expression of cytokeratin 19 was showed in primary SCTC, and negative in metastatic SCTC.

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

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.

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

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.

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.

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.

The diagnosis of plasmacytoma uses a diverse range of interdisciplinary techniques including serum protein electrophoresis, bone marrow biopsy, urine analysis for Bence Jones protein and complete blood count, plain film radiography, MRI and PET-CT.

Serum protein electrophoresis separates the proteins in the liquid part of the blood (serum), allowing the analysis of antibodies. Normal blood serum contains a range of antibodies and are said to be polyclonal, whereas serum from a person with plasmacytoma may show a monoclonal spike. This is due to an outgrowth of a single type of plasma cell that forms the plasmacytoma and produces a single type of antibody. The plasma cells are said to be monoclonal and the excessively produced antibody is known as monoclonal protein or paraprotein. Paraproteins are present in 60% of SPB and less than 25% of extramedullary plasmacytoma.

Bone marrow biopsies are performed to ensure the disease is localised; and in SPB or extramedullary plasmacytoma there will not be an increase of monoclonal plasma cells. Tissue biopsies of SPB and extramedullary plasmacytoma are used to assess the phenotype of the plasma cells. Histological analyses can be performed on these biopsies to see what cluster of differentiation (CD) markers are present and to assess monoclonality of the cells. CD markers can aid in the distinction of extramedullary plasmacytoma from lymphomas.

Skeletal surveys are used to ensure there are no other primary tumors within the axial skeleton. MRI can be used to assess tumor status and may be advantageous in detecting primary tumors that are not detected by plain film radiography. PET-CT may also be beneficial in detecting extramedullary tumours in individuals diagnosed with SPB. CT imaging may be better than plain film radiography for assessing bone damage.

An important distinction to be made is that a true plasmacytoma is present and not a systemic plasma cell disorder, such as multiple myeloma. The difference between plasmacytoma and multiple myeloma is that plasmacytoma lacks increased blood calcium, renal insufficiency, anemia and multiple bone lesions (collectively termed CRAB).

Treatment with conventional immunochemotherapy is usually indicated; in younger patients, allogeneic bone marrow transplantation may be curative.

In the absence of symptoms, many clinicians will recommend simply monitoring the patient; Waldenström himself stated "let well do" for such patients. These asymptomatic cases are now classified as two successively more pre-malignant phases, IgM monoclonal gammopathy of undetermined significance (i.e. IgM MGUS) and smoldering Waldenström's macroglobulinemia.

But on occasion, the disease can be fatal, as it was to the French president Georges Pompidou, who died in office in 1974. Mohammad Reza Shah Pahlavi, the Shah of Iran, also suffered from Waldenström's macroglobulinemia, which resulted in his ill-fated trip to the United States for therapy in 1979, leading to the Iran hostage crisis.

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.

T-PLL has the immunophenotype of a mature (post-thymic) T-lymphocyte, and the neoplastic cells are typically positive for pan-T antigens CD2, CD3, and CD7 and negative for TdT and CD1a. The immunophenotype CD4+/CD8- is present in 60% of cases, the CD4+/CD8+ immunophenotype is present in 25%, and the CD4-/CD8+ immunophenotype is present in 15% of cases.

Clonal rearrangements of the T-cell receptor (TCR) genes are a necessary condition for the diagnosis of this disease. The gene for the β chain of the TCR is found to be rearranged more often than the γ chain. of the TCR.

As the end stage of multiple myeloma that has failed or broken through one or more therapeutic regimens, sPCL continues to be highly refractory to various treatment regimens (<50%), very short response times of these regiments, and poor overall survival rates (median survival of 2-8 to months). Patients with sPCL may have short-lived responses to treatment regimens (as communicated in case reports) that include bortezomid but there are no established therapeutic regimens that have clearly been shown to improve their overall or median survival.

No distinct immunophenotype abnormality for CNL has been described.

See OHSU 2013 findings of gene CSF3R, mutation p. T6181

Several other illnesses can present with a monoclonal gammopathy, and the monoclonal protein may be the first discovery before a formal diagnosis is made: