Evidence is conflicting on the prognostic significance of chloromas in patients with acute myeloid leukemia. In general, they are felt to augur a poorer prognosis, with a poorer response to treatment and worse survival; however, others have reported chloromas associate, as a biologic marker, with other poor prognostic factors, and therefore do not have independent prognostic significance.

The first clue to a diagnosis of AML is typically an abnormal result on a complete blood count. While an excess of abnormal white blood cells (leukocytosis) is a common finding with the leukemia, and leukemic blasts are sometimes seen, AML can also present with isolated decreases in platelets, red blood cells, or even with a low white blood cell count (leukopenia). While a presumptive diagnosis of AML can be made by examination of the peripheral blood smear when there are circulating leukemic blasts, a definitive diagnosis usually requires an adequate bone marrow aspiration and biopsy as well as ruling out pernicious anemia (Vitamin B12 deficiency), folic acid deficiency and copper deficiency.

Marrow or blood is examined under light microscopy, as well as flow cytometry, to diagnose the presence of leukemia, to differentiate AML from other types of leukemia (e.g. acute lymphoblastic leukemia - ALL), and to classify the subtype of disease. A sample of marrow or blood is typically also tested for chromosomal abnormalities by routine cytogenetics or fluorescent "in situ" hybridization. Genetic studies may also be performed to look for specific mutations in genes such as "FLT3", nucleophosmin, and "KIT", which may influence the outcome of the disease.

Cytochemical stains on blood and bone marrow smears are helpful in the distinction of AML from ALL, and in subclassification of AML. The combination of a myeloperoxidase or Sudan black stain and a nonspecific esterase stain will provide the desired information in most cases. The myeloperoxidase or Sudan black reactions are most useful in establishing the identity of AML and distinguishing it from ALL. The nonspecific esterase stain is used to identify a monocytic component in AMLs and to distinguish a poorly differentiated monoblastic leukemia from ALL.

The diagnosis and classification of AML can be challenging, and should be performed by a qualified hematopathologist or hematologist. In straightforward cases, the presence of certain morphologic features (such as Auer rods) or specific flow cytometry results can distinguish AML from other leukemias; however, in the absence of such features, diagnosis may be more difficult.

The two most commonly used classification schemata for AML are the older French-American-British (FAB) system and the newer World Health Organization (WHO) system. According to the widely used WHO criteria, the diagnosis of AML is established by demonstrating involvement of more than 20% of the blood and/or bone marrow by leukemic myeloblasts, except in the three best prognosis forms of acute myeloid leukemia with recurrent genetic abnormalities (t(8;21), inv(16), and t(15;17)) in which the presence of the genetic abnormality is diagnostic irrespective of blast percent. The French–American–British (FAB) classification is a bit more stringent, requiring a blast percentage of at least 30% in bone marrow (BM) or peripheral blood (PB) for the diagnosis of AML. AML must be carefully differentiated from "preleukemic" conditions such as myelodysplastic or myeloproliferative syndromes, which are treated differently.

Because acute promyelocytic leukemia (APL) has the highest curability and requires a unique form of treatment, it is important to quickly establish or exclude the diagnosis of this subtype of leukemia. Fluorescent "in situ" hybridization performed on blood or bone marrow is often used for this purpose, as it readily identifies the chromosomal translocation [t(15;17)(q22;q12);] that characterizes APL. There is also a need to molecularly detect the presence of PML/RARA fusion protein, which is an oncogenic product of that translocation.

Diagnosis is usually based on repeated complete blood counts and a bone marrow examination following observations of the symptoms. Sometimes, blood tests may not show that a person has leukemia, especially in the early stages of the disease or during remission. A lymph node biopsy can be performed to diagnose certain types of leukemia in certain situations.

Following diagnosis, blood chemistry tests can be used to determine the degree of liver and kidney damage or the effects of chemotherapy on the patient. When concerns arise about other damage due to leukemia, doctors may use an X-ray, MRI, or ultrasound. These can potentially show leukemia's effects on such body parts as bones (X-ray), the brain (MRI), or the kidneys, spleen, and liver (ultrasound). CT scans can be used to check lymph nodes in the chest, though this is uncommon.

Despite the use of these methods to diagnose whether or not a patient has leukemia, many people have not been diagnosed because many of the symptoms are vague, non-specific, and can refer to other diseases. For this reason, the American Cancer Society estimates that at least one-fifth of the people with leukemia have not yet been diagnosed.

Definitive diagnosis of a chloroma usually requires a biopsy of the lesion in question. Historically, even with a tissue biopsy, pathologic misdiagnosis was an important problem, particularly in patients without a clear pre-existing diagnosis of acute myeloid leukemia to guide the pathologist. In one published series on chloroma, the authors stated that 47% of the patients were initially misdiagnosed, most often as having a malignant lymphoma.

However, with advances in diagnostic techniques, the diagnosis of chloromas can be made more reliable. Traweek et al. described the use of a commercially available panel of monoclonal antibodies, against myeloperoxidase, CD68, CD43, and CD20, to accurately diagnose chloroma via immunohistochemistry and differentiate it from lymphoma. Nowadays, immunohistochemical staining using monoclonal antibodies against CD33 and CD117 would be the mainstay of diagnosis. The increasingly refined use of flow cytometry has also facilitated more accurate diagnosis of these lesions.

The Düsseldorf score stratifies cases using four categories, giving one point for each; bone marrow blasts ≥5%, LDH >200U/L, haemoglobin ≤9g/dL and a platelet count ≤100,000/uL. A score of 0 indicates a low risk group' 1-2 indicates an intermediate risk group and 3-4 indicates a high risk group. The cumulative 2 year survival of scores 0, 1-2 and 3-4 is 91%, 52% and 9%; and risk of AML transformation is 0%, 19% and 54% respectively.

Acute myeloid leukemia is a curable disease; the chance of cure for a specific person depends on a number of prognostic factors.

Acute promyelocytic leukemia can be distinguished from other types of AML based on microscopic examination of the blood film or a bone marrow aspirate or biopsy as well as finding the characteristic rearrangement. Definitive diagnosis requires testing for the "PML/RARA" fusion gene. This may be done by polymerase chain reaction (PCR), fluorescent in situ hybridization (FISH), or conventional cytogenetics of peripheral blood or bone marrow. This mutation involves a translocation of the long arm of chromosomes 15 and 17. On rare occasions, a cryptic translocation may occur which cannot be detected by cytogenetic testing; on these occasions PCR testing is essential to confirm the diagnosis. Presence of multiple Auer rods on peripheral blood smear is highly suggestive of acute promyelocytic leukemia.

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.

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.

Following observation of the symptoms, the patients need to get complete blood counts and a bone marrow examination. If the patient has leukemia, the morphology and immunophenotype check is needed to make sure the type of leukemia.

The morphology of the blast in BAL is not certain. The cells could display both myeloid lineage and lymphoid or undifferentiated morphology. Therefore, the diagnosis cannot based on the morphology result. The immunophenotype check is the most important basis of the diagnosis of BAL.

Before 2008, the diagnosis of BAL was based on a score system proposed by the European Group for the Immunological Classification of Leukemias (EGIL) which could differentiate from other kinds of acute leukemia. The table shows this method.

If the score of only one lineage is higher than 2, the acute leukemia could be acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). According to the original EGIL scoring system BAL is defined when scores are over two points for both myeloid and T- or B- lymphoid lineages.

In 2008, WHO established a new and strict criteria standard for diagnosis of BAL. The presence of specific T-lymphoid antigens, cytoplasmic CD3 (cCD3), MPO and CD 19 became the most important standard for recognizing the lineage. Other B-lineage markers (CD22, CD79a, CD 10) and monocytic markers are also needed. Table 2 shows the method.

Compared with the EGIL scoring system, the current 2008 WHO criteria applied less but more specific markers to define the lineage of the blasts, and incorporated the intensity of markers expression into the diagnostic algorithm.

The diagnosis of BAL is so difficult that sometimes is misdiagnosed with AML or ALL because the morphology thus the therapy would not have a good effect.

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. Nearly all leukemias appearing in pregnant women are acute leukemias. 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. Chronic myelogenous leukemia can be treated with relative safety at any time during pregnancy with Interferon-alpha hormones. Treatment for chronic lymphocytic leukemias, which are rare in pregnant women, can often be postponed until after the end of the pregnancy.

The International Prognostic Scoring System (IPSS) was developed in the mid-1990s to assess the prognosis of MDS patients. This system stratifies cases into 2 groups; a lower-risk group (sub divided into low and intermediate-1) and a higher risk (subdivided into intermediate-2 and high). It uses the blast percentage, number of cytopaenias and bone marrow cytogenetics data to place cases of CMML into these groups. Due to the scoring system being developed for MDS, the more myeloproliferative cases of CMML (WBC >13x10) are excluded from the scoring system. Although the IPSS scoring system is used clinically, there is a high variability in each group. For this reason, new modalities for assessing prognosis in MDS (and CMML) are being developed.

In the past 5 years, the research for the mechanisms of BAL does not have a great progress. Some new translocate case of BAL has been reported, such as t(15,17) and t(12,13). For t(15;17), the blasts with morphology of acute lymphoblastic leukemia co-expressed in B-lymphoid and myeloid lineages, and the cytogenetic study showed that the 4q21 abnormalities and t(15;17). However, promyelocytic-retinoid acid receptor rearrangement was not found by fluorescence in situ hybridization on interphase nuclei. Researchers also found some new chemotherapy method for specific cases. For example, The chemotherapy for ALL and gemtuzuab ozogamicin without all-trans-retinoic acid remain complete remission of the BAL patients with t(15,17) for more than 3.7 years.

The detection of BCR-ABL1 chimeric gene neutrophils was also found a good method for diagnosis some cases of BAL.

Totally, there is no breakthrough research for the therapy or mechanisms of BAL in recent years. For most of BAL patients, there is no good therapy method because we still don’t fully understand the mechanisms of BAL. Thus, we have to learn more about the different cases, do more research on the mutation that lead BAL. Beside chemotherapy, we should develop new method such as gene drug for BAL therapy.

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.

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

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

Acute eosinophilic leukemia is treated as other subtypes of AML. Response to treatment is approximately the same as in other types of AML.

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.

Acute mast cell leukemia is extremely aggressive and has a grave prognosis. In most cases, multi-organ failure including bone marrow failure develops over weeks to months. Median survival after diagnosis is only about 6 months.

Information on prognosis is limited by the rarity of the condition. Prognosis appears to be no different to AML in general, taking into account other risk factors. Acute erythroid leukemia (M6) has a relatively poor prognosis. A 2010 study of 124 patients found a median overall survival of 8 months. A 2009 study on 91 patients found a median overall survival for erythroleukemia patients of 36 weeks, with no statistically significant difference to other AML patients. AEL patients did have a significantly shorter disease free survival period, a median of 32 weeks, but this effect was explained by other prognostic factors. That is, AEL is often associated with other risk factors, like monosomal karyotypes and a history of myelodysplastic syndrome. Prognosis is worse in elderly patients, those with a history of myelodysplastic syndrome, and in patients who had previously received chemotherapy for the treatment of a different neoplasm.

Acute promyelocytic leukemia represents 10-12% of AML cases. The median age is approximately 30–40 years, which is considerably younger than the other subtypes of AML (70 years). Incidence is higher among individuals of Latin American or South European origin. It can also occur as a secondary malignancy in those that receive treatment with topoisomerase II inhibitors (such as the anthracyclines and etoposide) due to the carcinogenic effects of these agents, with patients with breast cancer representing the majority of such patients. Around 40% of patients with APL also have a chromosomal abnormality such as trisomy 8 or isochromosome 17 which do not appear to impact on long-term outcomes.

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

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.

Acute erythroid leukemia is rare, accounting for only 3–5% of all acute myeloid leukemia cases. One study estimated an occurrence rate of 0.077 cases per 100,000 people each year. 64–70% of people with this condition are male, and most are elderly, with a median age of 65.

The morphology of cells was observed by means of bone marrow smear; the immunophenotype was detected by flow cytometry and immunohistochemistry assay.

Blasts more than 20%, with more than 50% of megakaryocytic phenotype.

In blood and bone marrow smears megakaryoblasts are usually medium-sized to large cells with a high nuclear-cytoplasmic ratio. Nuclear chromatin is dense and homogeneous. There is scanty, variable basophilic cytoplasm which may be vacuolated. An irregular cytoplasmic border is often noted in some of the megakaryoblasts and occasionally projections resembling budding atypical platelets are present. Megakaryoblasts lack myeloperoxidase (MPO) activity and stain negatively with Sudan black B. They are alpha naphthyl butyrate esterase negative and manifest variable alpha naphthyl acetate esterase activity usually in scattered clumps or granules in the cytoplasm. PAS staining also varies from negative to focal or granular positivity, to strongly positive staining. A marrow aspirate is difficult to obtain in many cases because of variable degree of myelofibrosis. More precise identification is by immunophenotyping or with electron microscopy (EM). Immunophenotyping using MoAb to megakaryocyte restricted antigen (CD41 and CD61) may be diagnostic.

Complete remission and long-term survival are more common in children than adults.

Prognosis depends upon the cause. One third of cases is associated with a t(1;22)(p13;q13) mutation in children. These cases carry a poor prognosis.

Another third of cases is found in Down syndrome. These cases have a reasonably fair prognosis.

The last third of cases may be heterogeneous, and carry a poor prognosis.