Meditations of an oncology geek

What’s the difference between a tumor and cancer?

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21 May 2011

This week I answer another inquiry from Peter Borak of San Diego, CA:

What’s the difference between a tumor and cancer?

That’s a great question. A tumor is the name for a swelling or lesion in the body caused by abnormal growth of cells. Cancer is the spread of tumors throughout the body. Tumors can either be:

1) Benign
2) Pre-cancerous
3) Malignant

Benign tumors are tumors that will most likely stay localized, not grow beyond a certain size, and not seed other tumors far away and disrupt distant organs. Benign tumors are actually fairly common. For instance, about 1 in 100 people have lipomas, which are fatty cysts that occasionally show up and grow under the skin and rarely reach more than 2cm in diameter. Many people have them and don’t even realize it. They are benign in the sense that they do not disrupt the surrounding skin, and they will not seed more lipomas in vital organs far away. They also do not usually cause any pain or discomfort. The cause of these tumors is unknown, but they do not pose any non-strictly cosmetic health concerns – like most benign tumors, they are easily removed via surgery.

Pre-cancerous tumors differ from benign tumors in that they are likely to become cancerous and spread, but they are usually removable and curable via surgery and are often considered “low grade” cancer. Pre-cancerous tumors can be distinguished from benign tumors by biopsy analysis by trained pathologists. (The image to the right is a cross-section of a cancerous breast tumor that would be immediately recognized as such by a pathologist) Also, pre-cancerous tumors tend to be hard or stiff to the touch, like a marble instead of a gummy bear.

Malignant tumors are prototypically cancer. They grow uncontrollably, disrupt local tissues, and spread and seed other tissues in the body where they grow uncontrollably and disrupt function. Again, pathologists (armed with low-tech microscopes) are very capable of distinguishing malignant tumors from pre-cancerous ones or benign ones.

So there you have it. Cancer is a disease of uncontrolled tumor growth and tumor spread – however, not all tumors are malignant, and not all tumors will necessarily become malignant.


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Written by Ryon

May 21st, 2011 at 12:56 pm

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4 Responses to 'What’s the difference between a tumor and cancer?'

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