A tumor, also known as a neoplasm, is an abnormal mass of tissue which may be solid or fluid-filled.
A tumor does not mean cancer - tumors can be benign (not cancerous), pre-malignant (pre-cancerous), or malignant (cancerous).
There are many different types of tumors and a variety of names for them - their names usually reflect their shape and the kind of tissue they appear in. Put simply, a tumor is a kind of lump or swelling, it does not necessarily pose a health threat.
Contents of this article:
Fast facts on tumors
Here are some key points about tumors. More detail and supporting information is in the main article.
- Tumor are not necessarily cancerous.
- Benign tumors cannot spread.
- Fibroids are benign tumors that grow on fibrous or connective tissue.
- Lipomas consist of adipose tissue.
- A premalignant tumor is one that is not yet cancerous but is about to be.
- Cancerous tumors are referred to as malignant.
- Metastasis is the term used to describe the process of a tumor spreading.
- An excisional biopsy involves removing an entire lump or surrounding area.
What is a tumor?
When doctors use the term tumor they are talking generically and not about the size of the lesion. A mass usually refers to a lump which is at least 20 mm (0.787 inches) in diameter at its widest point, while a nodule is less than 20 mm at its widest point.
Tumor sizes may vary enormously. In January 2012, Nguyen Duy Hai, a 32-year-old Vietnamese man underwent a 12-hour operation to remove a 200-pound tumor from his leg. Dr. McKay McKinnon, lead surgeon, had rated the success of the operation at just 50%. The surgery was a success.
Cancer stem cells may play a major role in tumor growth, three studies published in the journals Nature and Science revealed in August 2012. Scientists believe cancer might have its own stem cells that impact on the regrowth of tumors. They added that if further studies confirm their findings, the way we treat cancerous tumors may change dramatically.
A benign tumor (benign neoplasm) cannot metastasize - it cannot spread. Examples include uterine fibroids and moles. "Benign" means it is non-progressive, it remains as it is.
Most benign tumors are not harmful to human health. Even though they are not cancerous, some may press against nerves or blood vessels and cause pain or other negative effects. Benign tumors of endocrine tissues may result in the excessive production of some hormones.
Examples of benign tumors include:
Adenomas are tumors that arise from glandular epithelial tissue - epithelial tissue is the thin membrane that covers glands, organs and other structures in the body. A polyp in the colon is a type of adenoma. Other examples include pituitary adenoma, adrenocortical adenoma, basal cell adenoma, bile duct adenoma, chromophobe adenoma, follicular adenoma, hepatocellular adenoma, and nipple adenoma (there are many more).
Although adenomas are not cancerous, they can change and become so; then they are called adenocarcinomas.
Fibroids (fibromas) are benign tumors that grow on fibrous or connective tissue of any organ in the body. Uterine fibroids are common. Uterine fibroids can cause vaginal bleeding, pelvic pain or discomfort, and urinary incontinence.
A soft fibroma of the eyelid. Photo credit: Oliver Riesen
The fibroma durum (hard fibroma) is made up of many fibers and few cells. The fibroma molle (soft fibroma) is made up of several loosely connected cells and less fibroid tissue. Soft fibroma is usually found in the armpits, groin, neck and eyelids.
There are many types of fibromas, such as angiofibroma, cystic fibroma (fibroma cysticum), myxofibroma (fibroma myxomatodes), nonossifying fibroma, ossifying fibroma, cemento-ossifying fibroma, pleomorphic fibroma, fibroma of tendon sheath nuchal fibroma, chondromyxoid fibroma, desmoplasmic fibroma, collagenous fibroma, and perifollicular fibroma.
Some fibromas can cause symptoms and may require surgical removal. Rarely, fibroids can change and eventually become cancerous, they are then called fibrosarcomas.
A hemangiomas on the scalp of a child
Hemangiomas are benign tumors which consists of a collection of too many blood cells. They can sometimes be seen on the surface of the skin and are colloquially called strawberry marks. The majority of hemangiomas appear at birth and gradually go away after some months or years.
Hemangiomas do not usually require any treatment. If they affect the patient's ability to eat, hear or see, the doctor may recommend treatment with corticosteroids. If the patient is over 10 years of age, they are more commonly removed today using laser surgery.
Lipomas are the most common form of soft-tissue tumor. Lipomas consist of adipose tissue (fat cells). Most of them are very small, painless, soft to the touch, and generally movable. They are more common among people aged 40+ years. Experts disagree on whether lipomas can change and become cancerous (malignant).
There are many kinds of lipomas, such as angiolipoleiomyoma, angiolipoma, chondroid lipoma, corpus callosum lipoma, hibernoma, intradermal spindle cell lipoma, neural fibrolipoma, pleomorphic lipomas, and superficial subcutaneous lipoma (the most common type, found just below the skin's surface).
On the next page, we look at premalignant and malignant tumors. On the final page we discuss tumor biopsy procedures and the common prefixes used in naming tumors and cancers.