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What Is Leukemia? Blood Cancer Explained

Just been diagnosed with Leukemia? Start here instead

A plain-language explanation of leukemia, a group of blood cell cancers, based on National Cancer Institute resources.

Source:MedlinePlus — Leukemia

Review status: AI-assisted, source checked. Not reviewed by a clinician. How we check pages

The short answer

Leukemia is a broad term for cancers of the blood cells. The type depends on which blood cell becomes cancer and whether it grows quickly or slowly. It happens most often in adults older than 55, but it is also the most common cancer in children younger than 15.

  • Leukemia is a broad term for cancers of the blood cells.

  • The type of leukemia depends on which blood cell becomes cancer and how fast it grows.

  • Leukemia occurs most often in adults older than 55.

  • It is also the most common cancer in children younger than 15.

Subjective: What you might experience

This section describes the symptoms and history a patient might report to their doctor.

Fatigue, weakness, or shortness of breath (from anemia).

Easy bruising or bleeding, frequent nosebleeds, or bleeding gums.

Frequent or lingering infections and fevers.

Bone or joint pain, night sweats, and unexplained weight loss.

Swollen lymph nodes, or fullness/discomfort from an enlarged spleen.

Symptoms can come on suddenly (acute) or gradually (chronic).

Objective: Tests and findings

Complete blood count showing abnormal numbers of white cells, red cells, or platelets.

Peripheral blood smear examined for abnormal (blast) cells.

Bone marrow aspiration and biopsy

the key test to confirm and classify leukemia.

Flow cytometry, cytogenetics, and molecular testing to identify the subtype and markers.

Lumbar puncture in some types to check for central nervous system involvement.

Interactive anatomy guide

Explore where cancers start and how they are found, on an interactive body map.

Open the anatomy guide

Assessment: Staging and prognosis

Classified as acute or chronic and by cell line (lymphocytic or myeloid): ALL, AML, CLL, CML.

Diagnosis and subtype confirmed by marrow, flow cytometry, and genetic testing.

Instead of TNM, risk is stratified by genetic/molecular features, age, and blood counts.

Specific markers (e.g., Philadelphia chromosome in CML) directly guide targeted therapy.

Plan: The treatment approach

Acute leukemias

chemotherapy in phases, sometimes with targeted therapy; stem cell transplant for some.

CML

targeted tyrosine kinase inhibitors are the mainstay.

CLL

watchful waiting when stable, or targeted/immunotherapy when treatment is needed.

Supportive care

transfusions, infection prevention, and treatment of complications.

Clinical trials and long-term monitoring of blood counts and marrow.

These are simplified, educational SOAP-style summaries showing the kinds of findings clinicians document when evaluating each cancer, based on National Cancer Institute resources. They describe typical diagnostic criteria and workups — not a real patient, and not medical advice. Real clinical notes are individualized. Always rely on your own care team. Based on National Cancer Institute educational content. Educational only — not medical advice.

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Common questions

What is leukemia?

Leukemia is a broad term for cancers of the blood cells. The type depends on which kind of blood cell becomes cancer and whether it grows quickly or slowly.

Who gets leukemia?

Leukemia occurs most often in adults older than 55. It is also the most common cancer in children younger than 15.

Are there different kinds of leukemia?

Yes. Leukemia has several types, including acute lymphoblastic leukemia, acute myeloid leukemia, chronic lymphocytic leukemia, chronic myeloid leukemia, and hairy cell leukemia.

Does the speed of growth matter?

Yes. Part of what defines a type of leukemia is whether it grows quickly (acute) or slowly (chronic).

Is there a screening test for leukemia?

Ask your healthcare team whether any testing fits your situation. They can explain more about your own risk.

Questions to ask your doctor

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Get urgent help

Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.

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Prepared by Cancer Explained's AI-assisted editorial system

Written from federal health agency material and compared with the source cited below.

Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.

Sources last checked: 2026-08-13 what this meansLast updated: 2026-09-30Next planned review: 2027-07-21

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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.

Editorial status — Source checked. This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.

General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.

Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.

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Knowledge check

0 of 4 answered

  1. Q1.According to this article, what is leukemia?
  2. Q2.According to this article, what two things decide the type of leukemia?
  3. Q3.According to this article, in which group does leukemia occur most often?
  4. Q4.According to this article, what do the words 'acute' and 'chronic' point to?

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How this page was created

Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.

Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.

Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.

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