What's the difference between a tumor and a cyst? Could a cyst be cancerous?

Tumors and cysts are two distinct types of growths.

  • Cyst. A cyst is a sac that may be filled with air, fluid or other material. A cyst can form in any part of the body, including bones, organs and soft tissues. Most cysts are noncancerous, also called benign, but sometimes cancer can cause a cyst.
  • Tumor. A tumor is any mass of tissue or swelling. Like a cyst, a tumor can form in any part of the body. A tumor can be benign or cancerous, also called malignant.

Cysts that appear uniform after an ultrasound exam or a CT scan are almost always benign and should simply be watched.

If the cyst has solid components, it may be benign or malignant and should have further evaluation. Often this is done with repeat imaging to see if the cyst grows over time.

The best test to determine whether a cyst or tumor is benign or malignant is a biopsy. A biopsy is a procedure to remove a sample of tissue for testing in a lab to see if it is cancer.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email.

Aug. 20, 2025 See more Expert Answers

See also

  1. 10 great health foods
  2. Adenocarcinoma: How this type of cancer affects prognosis
  3. Adjuvant therapy: Treatment to keep cancer from returning
  4. Alternative cancer treatments: 11 options to consider
  5. Atypical cells: Are they cancer?
  6. Biological therapy for cancer
  7. Biopsy: Types of biopsy procedures used to diagnose cancer
  8. Blood Basics
  9. Bone marrow transplant
  10. Bone scan
  11. Brachytherapy
  12. Cancer
  13. Cancer blood tests: Lab tests used in cancer diagnosis
  14. Cancer causes: Popular myths about the causes of cancer
  15. Cancer diagnosis: 11 tips for coping
  16. Cancer fatigue: Why it occurs and how to cope
  17. Cancer pain: Relief is possible
  18. Cancer prevention: 7 tips to reduce your risk
  19. Cancer risk: What the numbers mean
  20. Cancer surgery: Physically removing cancer
  21. Cancer survival rate: What it means for your prognosis
  22. Cancer survivors: Care for your body after treatment
  23. Cancer survivors: Late effects of cancer treatment
  24. Cancer survivors: Managing your emotions after cancer treatment
  25. Cancer treatment
  26. Cancer treatment myths: Any truth to these common beliefs?
  27. CAR-T cell therapy
  28. Chemo targets
  29. Chemotherapy
  30. Chemotherapy and hair loss: What to expect during treatment
  31. Chemotherapy and sex: Is sexual activity OK during treatment?
  32. Chemotherapy nausea and vomiting: Prevention is best defense
  33. Chemotherapy side effects: A cause of heart disease?
  34. Complete blood count (CBC)
  35. CT scan
  36. Curcumin: Can it slow cancer growth?
  37. Diarrhea: Cancer-related causes and how to cope
  38. Doppler ultrasound: What is it used for?
  39. Dysphagia
  40. Eating during cancer treatment: Tips to make food tastier
  41. Fertility preservation: Understand your options before cancer treatment
  42. Heart cancer: Is there such a thing?
  43. High-dose vitamin C: Can it kill cancer cells?
  44. Honey: An effective cough remedy?
  45. How cancer spreads
  46. Infographic: Cancer Clinical Trials Offer Many Benefits
  47. Infographic: CAR-T Cell Therapy
  48. Infographic: Mayo Clinic CAR-T Cell Therapy Program
  49. Intensity-modulated radiation therapy (IMRT)
  50. Laryngitis
  51. Low blood cell counts: Side effects of cancer treatment
  52. Magic mouthwash
  53. Medical marijuana
  54. Monoclonal antibody medicines for cancer: How they work
  55. Mort Crim and Cancer
  56. Mouth sores caused by cancer treatment: How to cope
  57. MRI
  58. MRI
  59. Needle biopsy
  60. No appetite? How to get nutrition during cancer treatment
  61. Palliative care
  62. PALS (Pets Are Loving Support)
  63. PICC line placement
  64. Pressurized intraperitoneal aerosol chemotherapy (PIPAC)
  65. Proton beam therapy
  66. Proton therapy
  67. Radiation therapy
  68. Seeing inside the heart with MRI
  69. Self-Image During Cancer
  70. Sisters' Bone Marrow Transplant
  71. Sleep tips: 6 steps to better sleep
  72. Small cell, large cell cancer: What this means
  73. Stem cell transplant
  74. Stem cells: What they are and what they do
  75. Stereotactic radiosurgery
  76. Ultrasound
  77. When cancer returns: How to cope with cancer recurrence
  78. X-ray