Initial symptoms can be nonspecific, particularly in children. Over 50% of children with leukemia had one or more of five features: a liver one can feel (64%), a spleen one can feel (61%), pale complexion (54%), fever (53%), and bruising (52%). Additionally, recurrent infections, feeling tired, arm or leg pain, and enlarged lymph nodes can be prominent features. The B symptoms, such as fever, night sweats, and weight loss, are often present as well.

Central nervous system (CNS) symptoms such cranial neuropathies due to meningeal infiltration are identified in less than 10% of adults and less than 5% of children, particularly mature B-cell ALL (Burkitt leukemia) at presentation.

The signs and symptoms of ALL are variable and include:

- Generalized weakness and feeling tired

- Anemia

- Dizziness

- Headache, vomiting, lethargy, nuchal rigidity, or cranial nerve palsies (CNS involvement)

- Frequent or unexplained fever and infection

- Weight loss and/or loss of appetite

- Excessive and unexplained bruising

- Bone pain, joint pain (caused by the spread of "blast" cells to the surface of the bone or into the joint from the marrow cavity)

- Breathlessness

- Enlarged lymph nodes, liver and/or spleen

- Pitting edema (swelling) in the lower limbs and/or abdomen

- Petechiae, which are tiny red spots or lines in the skin due to low platelet levels

- Testicular enlargement

- Mediastinal mass

Patients usually present with constitutional symptoms (malaise, weight loss, fatigue), and hepatosplenomegaly is commonly found on physical exam. Lymphadenopathy is also found to a lesser extent. Due to the aggressive nature of the disease, patients may initially present at a more advanced stage, with coagulopathies, hemophagocytic syndrome, and multi-organ failure.

BAL has similar symptoms with other types of leukemia, but usually more serious.

Symptoms caused by bone marrow damage

Bruising, spotting: the reason is lack of platelets, it is very common in BAL patients, most of patients die due to the

Anemia: Because the decline of hematopoietic function, need blood transfusion therapy

Persistent fever, infection prolonged healing:

Diffuse hemorrhage: also called Septicemia, which is dangerous and might lead to death.

Symptoms caused by blood cancer cells infiltration into tissues:

Lymphadenopathy

Joint pain

Swelling of the gums

Hepatoslenomegaly

Headache and vomiting: blood cancer infiltration into the wear performance of the central nervous system.

Skin lumps: Because look was slightly green, also known as the "Green tumor."

Pericardial or pleural effusion

Most signs and symptoms of AML are caused by the replacement of normal blood cells with leukemic cells. A lack of normal white blood cell production makes people more susceptible to infections; while the leukemic cells themselves are derived from white blood cell precursors, they have no infection-fighting capacity. A drop in red blood cell count (anemia) can cause fatigue, paleness, and shortness of breath. A lack of platelets can lead to easy bruising or bleeding with minor trauma.

The early signs of AML are often vague and nonspecific, and may be similar to those of influenza or other common illnesses. Some generalized symptoms include fever, fatigue, weight loss or loss of appetite, shortness of breath, anemia, easy bruising or bleeding, petechiae (flat, pin-head sized spots under the skin caused by bleeding), bone and joint pain, and persistent or frequent infections.

Enlargement of the spleen may occur in AML, but it is typically mild and asymptomatic. Lymph node swelling is rare in AML, in contrast to acute lymphoblastic leukemia. The skin is involved about 10% of the time in the form of leukemia cutis. Rarely, Sweet's syndrome, a paraneoplastic inflammation of the skin, can occur with AML.

Some people with AML may experience swelling of the gums because of infiltration of leukemic cells into the gum tissue. Rarely, the first sign of leukemia may be the development of a solid leukemic mass or tumor outside of the bone marrow, called a chloroma. Occasionally, a person may show no symptoms, and the leukemia may be discovered incidentally during a routine blood test.

The most common symptoms in children are easy bruising, pale skin, fever, and an enlarged spleen or liver.

Damage to the bone marrow, by way of displacing the normal bone marrow cells with higher numbers of immature white blood cells, results in a lack of blood platelets, which are important in the blood clotting process. This means people with leukemia may easily become bruised, bleed excessively, or develop pinprick bleeds (petechiae).

White blood cells, which are involved in fighting pathogens, may be suppressed or dysfunctional. This could cause the patient's immune system to be unable to fight off a simple infection or to start attacking other body cells. Because leukemia prevents the immune system from working normally, some patients experience frequent infection, ranging from infected tonsils, sores in the mouth, or diarrhea to life-threatening pneumonia or opportunistic infections.

Finally, the red blood cell deficiency leads to anemia, which may cause dyspnea and .

Some patients experience other symptoms, such as feeling sick, having fevers, chills, night sweats, feeling fatigued and other flu-like symptoms. Some patients experience nausea or a feeling of fullness due to an enlarged liver and spleen; this can result in unintentional weight loss. Blasts affected by the disease may come together and become swollen in the liver or in the lymph nodes causing pain and leading to nausea.

If the leukemic cells invade the central nervous system, then neurological symptoms (notably headaches) can occur. Uncommon neurological symptoms like migraines, seizures, or coma can occur as a result of brain stem pressure. All symptoms associated with leukemia can be attributed to other diseases. Consequently, leukemia is always diagnosed through medical tests.

The word "leukemia", which means 'white blood', is derived from the characteristic high white blood cell count that presents in most afflicted patients before treatment. The high number of white blood cells are apparent when a blood sample is viewed under a microscope, with the extra white blood cells frequently being immature or dysfunctional. The excessive number of cells can also interfere with the level of other cells, causing further harmful imbalance in the blood count.

Some leukemia patients do not have high white blood cell counts visible during a regular blood count. This less-common condition is called "aleukemia". The bone marrow still contains cancerous white blood cells which disrupt the normal production of blood cells, but they remain in the marrow instead of entering the bloodstream, where they would be visible in a blood test. For an aleukemic patient, the white blood cell counts in the bloodstream can be normal or low. Aleukemia can occur in any of the four major types of leukemia, and is particularly common in hairy cell leukemia.

"T-cell leukemia" describes several different types of lymphoid leukemias which affect T cells.

The most common T-cell leukemia is precursor T-cell lymphoblastic leukemia. It causes 15% of acute leukemias in childhood, and also 40% of lymphomas in childhood. It is most common in adolescent males. Its morphology is identical to that of "precursor B-cell lymphoblastic leukemia". Cell markers include TdT, CD2, CD7. It often presents as a mediastinal mass because of involvement of the thymus. It is highly associated with NOTCH1 mutations.

Other types include:

- Large granular lymphocytic leukemia

- Adult T-cell leukemia/lymphoma

- T-cell prolymphocytic leukemia

In practice, it can be hard to distinguish T-cell leukemia from T-cell lymphoma, and they are often grouped together.

People affected by T-cell prolymphocytic leukemia typically have systemic disease at presentation, including enlargement of the liver and spleen, widespread enlargement of the lymph nodes, and skin infiltrates.

Due to the systemic nature of this disease, leukemic cells can be found in peripheral blood, lymph nodes, bone marrow, spleen, liver, and skin. A high lymphocyte count (> 100 x 10/L) along with low amounts of red blood cells and platelets in the blood are common findings. HTLV-1 serologies are negative, and serum immunoglobins are within normal limits with no paraproteins present.

Historically, they have been most commonly divided by the stage of maturation at which the clonal (neoplastic) lymphoid population stopped maturing:

- Acute lymphoblastic leukemia

- Chronic lymphocytic leukemia

However, the influential WHO Classification (published in 2001) emphasized a greater emphasis on cell lineage. To this end, lymphoid leukemias can also be divided by the type of cells affected:

- B-cell leukemia

- T-cell leukemia

- NK-cell leukemia

The most common type of lymphoid leukemia is B-cell chronic lymphocytic leukemia.

Clinically and pathologically, leukemia is subdivided into a variety of large groups. The first division is between its "acute" and "chronic" forms:

- Acute leukemia is characterized by a rapid increase in the number of immature blood cells. The crowding that results from such cells makes the bone marrow unable to produce healthy blood cells. Immediate treatment is required in acute leukemia because of the rapid progression and accumulation of the malignant cells, which then spill over into the bloodstream and spread to other organs of the body. Acute forms of leukemia are the most common forms of leukemia in children.

- Chronic leukemia is characterized by the excessive buildup of relatively mature, but still abnormal, white blood cells. Typically taking months or years to progress, the cells are produced at a much higher rate than normal, resulting in many abnormal white blood cells. Whereas acute leukemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy. Chronic leukemia mostly occurs in older people, but can occur in any age group.

Additionally, the diseases are subdivided according to which kind of blood cell is affected. This divides leukemias into lymphoblastic or "lymphocytic leukemias" and myeloid or "myelogenous leukemias":

- In lymphoblastic or lymphocytic leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form lymphocytes, which are infection-fighting immune system cells. Most lymphocytic leukemias involve a specific subtype of lymphocyte, the B cell.

- In myeloid or myelogenous leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form red blood cells, some other types of white cells, and platelets.

Combining these two classifications provides a total of four main categories. Within each of these main categories, there are typically several subcategories. Finally, some rarer types are usually considered to be outside of this classification scheme.

Most people are diagnosed without symptoms as the result of a routine blood test that shows a high white blood cell count. Less commonly, CLL may present with enlarged lymph nodes without a high white blood cell count or no evidence of the disease in the blood. This is referred to as small lymphocytic lymphoma. In some individuals, the disease comes to light only after the cancerous cells overwhelm the bone marrow resulting in anemia producing tiredness or weakness.

Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruising, enlarged lymph nodes, or bone pain. As an acute leukemia, ALL progresses rapidly and is typically fatal within weeks or months if left untreated.

Most cases occur due to an unknown reason. Genetic risk factors may include Down syndrome, Li-Fraumeni syndrome, or neurofibromatosis type 1. Environment risk factors may include significant radiation exposure or prior chemotherapy. Evidence regarding electromagnetic fields or pesticides is unclear. Some hypothesize that an abnormal immune response to a common infection may be a trigger. The underlying mechanism involves multiple genetic mutations that results in rapid cell division. The excessive immature lymphocytes in the bone marrow interfere with the production of new red blood cells, white blood cells, and platelets. Diagnosis is typically based on blood tests and bone marrow examination.

ALL is typically treated initially with chemotherapy aimed at bringing about remission. This is then followed by further chemotherapy typically over a number of years. Additional treatments may include intrathecal chemotherapy or radiation therapy if spread to the brain has occurred. Stem cell transplantation may be used if the disease recurs following standard treatment. Additional treatments such as immunotherapy are being studied.

ALL affected about 876,000 people globally in 2015 and resulted in about 111,000 deaths. It occurs most commonly in children, particularly those between the ages of two and five. In the United States it is the most common cause of cancer and death from cancer among children. ALL is notable for being the first disseminated cancer to be cured. Survival for children increased from under 10% in the 1960s to 90% in 2015. Survival rates remain lower for babies (50%) and adults (35%).

Symptoms of Richter’s transformation in a CLL patient include fever (without infection), an elevated serum levels of lactate dehydrogenase, and rapidly enlarging lymph nodes. While about 8% of all CLL patients will have elevated levels of serum lactate dehydrogenase (LDH), more than 50% of CLL patients with Richter's transformation will have elevated LDH levels.

Richter's can appear suddenly, even in patients who were in remission.

It is postulated that the originating cell line for this disease is a mature (post-thymic) T-cell.

In hairy cell leukemia, the "hairy cells" (malignant B lymphocytes) accumulate in the bone marrow, interfering with the production of normal white blood cells, red blood cells, and platelets. Consequently, patients may develop infections related to low white blood cell count, anemia and fatigue due to a lack of red blood cells, or easy bleeding due to a low platelet count. Leukemic cells may gather in the spleen and cause it to swell; this can have the side effect of making the person feel full even when he or she has not eaten much.

Hairy cell leukemia is commonly diagnosed after a routine blood count shows unexpectedly low numbers of one or more kinds of normal blood cells, or after unexplained bruises or recurrent infections in an otherwise apparently healthy patient.

Platelet function may be somewhat impaired in HCL patients, although this does not appear to have any significant practical effect. It may result in somewhat more mild bruises than would otherwise be expected for a given platelet count or a mildly increased bleeding time for a minor cut. It is likely the result of producing slightly abnormal platelets in the overstressed bone marrow tissue.

Patients with a high tumor burden may also have somewhat reduced levels of cholesterol, especially in patients with an enlarged spleen. Cholesterol levels return to more normal values with successful treatment of HCL.

This disease is typically found and diagnosed in peripheral blood, and while it can involve any organ, it is usually found in the spleen, liver, and bone marrow.

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

Richter's syndrome (RS), also known as Richter's transformation, is a transformation which occurs in about 5-10% of B cell chronic lymphocytic leukemia (CLL) and hairy cell leukemia into a fast-growing diffuse large B cell lymphoma, a variety of non-Hodgkin lymphoma which is refractory to treatment and carries a bad prognosis. There is also a less common variant in which the CLL changes into a Hodgkin's lymphoma. Rarely, transformations to a form of myeloid leukemia have been observed. These extraordinarily rare transformations carry a very poor prognosis.

Richter's transformation affects about 5% of CLL patients at some point during their lives.

Chronic lymphoid leukemia (CLL) is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell). Early on there is typically no symptoms. Latter non-painful lymph nodes swelling, feeling tired, fever, or weight loss for no clear reason may occur. Enlargement of the spleen and anemia may also occur. It typically worsens gradually.

Risk factors include having a family history of the disease. Agent Orange and certain insecticides might also be a risk. CLL results in the build up of B cell lymphocytes in the bone marrow, lymph nodes, and blood. These cells do not function well and crowd out healthy blood cells. It is divided into two main types those with a mutated IGHV gene and those without. Diagnosis is typically based on blood tests finding high numbers of mature lymphocytes and smudge cells.

Management of early disease is generally with watchful waiting. Infections should more readily be treated with antibiotics. In those with significant symptoms chemotherapy or immunotherapy may be used. The medications fludarabine, cyclophosphamide, and rituximab are typically the initial treatment in those who are otherwise healthy.

CLL affected about 904,000 people globally in 2015 and resulted in 60,700 deaths. The disease most common occurs in people over the age of 50. Males are affected more often than females. It is much less common in people from Asia. Five-year survival following diagnosis is approximately 83% in the United States. It represents less than 1% of deaths from cancer.

B-cell prolymphocytic leukemia is a more aggressive, but still treatable, form of leukemia. The malignant B cells are larger than average. The name is commonly abbreviated B-PLL.

It can involve deletions from chromosome 11 and chromosome 13.

It has been suggested that some cases may represent a variant of mantle cell lymphoma.

It has a relatively poor prognosis.

Acute biphenotypic leukaemia is an uncommon type of leukemia which arises in multipotent progenitor cells which have the ability differentiating into both myeloid and lymphoid lineages. It is a subtype of "leukemia of ambiguous lineage".

The direct reason lead BAL is still not clear. BAL can be de novo or secondary to previous cytotoxic therapy. Many factors, such as virus, hereditary factors, radiation, might have relationship with BAL.

BAL is hard to treat, usually the chemotherapy is chosen according to the morphology of the blast (ALL or AML). The stem cell transplantation is highly recommended.

About 5% of acute leukaemia cases are BAL. BAL could occur in all the age of the people, but more in adults than in children.

This disease is known for an indolent clinical course and incidental discovery. The most common physical finding is moderate splenomegaly. B symptoms are seen in a third of cases, and recurrent infections due to the associated neutropenia are seen in almost half of cases.

Rheumatoid arthritis is commonly observed in people with T-LGLL, leading to a clinical presentation similar to Felty's syndrome. Signs and symptoms of anemia are commonly found, due to the association between T-LGLL and erythroid hypoplasia.

Precursor B-cell lymphoblastic leukemia is a form of lymphoid leukemia in which too many B-cell lymphoblasts (immature white blood cells) are found in the blood and bone marrow. It is the most common type of acute lymphoblastic leukemia (ALL). It is sometimes additionally classified as a lymphoma, as designated "leukemia/lymphoma".

It consists of the following subtypes:

- t(9;22)-BCR/ ABL

- t(v;11q23)-MLL rearrangement

- t(1;19)-E2A/PBX1

- t(12;21)-ETV/ CBFα

- t(17;19)-E2A-HLF

T-cell leukemia describes several different types of lymphoid leukemia which affect T cells.

Types include:

- Large granular lymphocytic leukemia

- Adult T-cell leukemia/lymphoma

- T-cell prolymphocytic leukemia

In practice, it can be hard to distinguish T-cell leukemia from T-cell lymphoma, and they are often grouped together.

Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cells. Symptoms may include feeling tired, shortness of breath, easy bruising and bleeding, and increased risk of infection. Occasionally spread may occur to the brain, skin, or gums. As an acute leukemia, AML progresses rapidly and is typically fatal within weeks or months if left untreated.

Risk factors include smoking, previous chemotherapy or radiation therapy, myelodysplastic syndrome, and exposure to the chemical benzene. The underlying mechanism involves replacement of normal bone marrow with leukemia cells, which results in a drop in red blood cells, platelets, and normal white blood cells. Diagnosis is generally based on bone marrow aspiration and specific blood tests. AML has several subtypes; for which treatments and outcomes may vary.

AML is typically initially treated with chemotherapy aimed at inducing remission. People may than go on to receive additional chemotherapy, radiation therapy, or a stem cell transplant. The specific genetic mutations present within the cancer cells may guide therapy, as well as determine how long that person is likely to survive. Arsenic trioxide may be tried in cases that have recurred following usual treatments.

AML affected about one million people globally in 2015 and resulted in 147,000 deaths. It most commonly occurs in older adults. Males are affected more often than females. AML is curable in about 35% of people under 60 years old and 10% over 60 years old. Older people who are not healthy enough to receive intensive chemotherapy have a typical survival of 5–10 months. It accounts for roughly 1.8% of cancer deaths in the United States.

Acute mast cell leukemia is a rapidly progressive disorder with leukemic mast cells in blood and in large numbers in marrow. The common signs and symptoms include fever, headache, flushing of face and trunk. The typical cutaneous mast cell infiltrates of urticaria pigmentosa are usually not present before, during, or after diagnosis in patients who have mast cell leukemia. Symptoms include abdominal pain, bone pain, and peptic ulcer which are more prevalent than in other subtypes of acute myeloid leukemia. These former symptoms are due to release of a substance called histamine from neoplastic mast cells. Enlargement of the liver and spleen, or hepatosplenomegaly is characteristic. The mast cells release also many anticoagulants like heparin which can lead to serious bleeding. Liver and splenic dysfunction also contributes to hemorrhage. Involvement of the bone can lead to osteoporosis. Abdominal ultrasound or computerized tomography (CT) scanning is used to look for hepatosplenomegaly and lymphadenopathy. Plain radiography and bone densitometry can be used to assess bone involvement and the presence of osteoporosis. Endoscopy and biopsy can be useful if gut involvement is suspected.