The short answer
Solid tumors form a lump in an organ or tissue. Blood cancers such as leukemia generally do not form a solid tumor. Ask your care team how your type is tested and treated.
Solid tumors are masses that grow in organs or tissues, like the breast or lung.
Blood cancers begin in blood-forming tissue or immune cells.
Leukemias generally do not form a solid tumor.
Cancers of the blood, such as leukemias, generally do not form solid tumors.
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The whole article, with every detail and caution.
This page is for anyone who wants to know how blood cancers differ from cancers that form a lump. It explains how each is found, staged, and treated.
The simple version
Most cancers form a solid mass called a tumor. That is a lump of abnormal cells. Blood cancers work differently. In leukemia, abnormal blood cells build up in the blood and bone marrow instead. Both are cancer, and your care team will explain how yours is tested and treated.
What makes a tumor solid
A solid tumor is an abnormal mass of tissue. It can form in the breast, lung, colon, or another organ. NCI says many cancers form solid tumors, but cancers of the blood, such as leukemias, generally do not. How a solid tumor is staged and treated depends on the cancer type, so ask your care team about your own plan.
How blood cancers are different
Leukemia is a cancer of the blood cells. NCI says large numbers of abnormal white blood cells build up in the blood and bone marrow. Bone marrow is the soft tissue inside bones where blood cells are made.
Lymphoma is a cancer of the lymphatic system. NCI says abnormal lymphocytes, a type of white blood cell, build up in lymph nodes, lymph vessels, and other organs of the body.
Multiple myeloma is a cancer of plasma cells. NCI says myeloma cells build up in the bone marrow and can form tumors in many bones of the body.
How diagnosis and staging differ
The tests used depend on the type of cancer. Your care team will explain which tests are used for yours and why. Because leukemia cells build up in the blood and bone marrow, tests of those tissues can be part of the work-up.
How treatment differs
Treatment depends on the type of cancer and your situation, so your plan may differ from someone else's. A stem cell transplant is one treatment used mainly for blood-related cancers such as leukemia, lymphoma, and multiple myeloma. NCI says it restores blood stem cells in people who have had theirs destroyed by high doses of chemotherapy or radiation therapy.
Why this distinction matters for you
Understanding which category your cancer falls into can help you ask more useful questions at your next appointment. If you are wondering why your plan looks different from someone else's, ask your care team.
Blood counts
Cancer treatment can lower blood counts. NCI says platelets help your blood clot, so low platelets make bruising and bleeding easier. Call your care team right away for bleeding that will not stop, black or bloody stools, red or pink urine, or severe headache, vision changes, or confusion. Your team will tell you how often your counts are checked and when to call.
What to ask your doctor
- Is my cancer a solid tumor or a blood cancer, and how does that shape my options?
- What tests are used to monitor my cancer?
- Why is surgery, or is it not, part of my plan?
- How often will my blood counts be checked, and what symptoms mean I should call the team?
Sources
Common questions
What is a solid tumor?
A solid tumor is an abnormal mass of tissue. Cancers of the breast, lung, colon, and prostate are examples.
What counts as a blood cancer?
Blood cancers include leukemias, lymphomas, and myeloma. They begin in blood-forming tissue such as bone marrow or in immune-system cells.
Why does the difference matter?
Cancers that form solid tumors and cancers of the blood behave differently. Leukemia cells build up in the blood and bone marrow instead of forming a solid mass. Ask your care team how your type is tested, staged, and treated.
Can blood cancers form masses?
NCI says abnormal lymphocytes in lymphoma build up in lymph nodes, lymph vessels, and other organs, and myeloma cells can create tumors in several bones. Leukemia generally does not form a solid tumor.
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Written by: Cancer ExplainedSources last checked: 2026-07-14 what this meansLast updated: 2026-10-16Next planned review: 2028-07-14
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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.
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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