Cancer, Neoplasia, Tumor, NeoplasmThe word cancer comes from the Latin (originally Greek) derived term for crab, because of the way a cancer adheres to any part that it seizes upon in an obstinate manner like the crab. Hippocrates first described cancer as having a central body with the tendency to reach out and spread like "the arms of a crab." Besides the popular, generic term "cancer" used by most people, there is another more technical term: neoplasia. Neoplasia (neo = new, plasia = tissue or cells) or neoplasm literally means new tissue in Greek. This indicates that cancers are actually new growths of cells in the body. Show
Another term for cancer is "malignant tumor." Tumor literally means "swelling" or "mass." In this case, it refers to a mass of non-structured new cells, which have no known purpose in the physiological function of the body. There are two general types of tumors: benign (non-cancerous) tumors and malignant (cancerous) tumors. A benign tumor is composed of cells that will not invade other unrelated tissues or organs of the body, although it may continue to grow in size abnormally. A malignant tumor is composed of cells that invade the basement membrane and invade or spread to other parts of the body. This occurs either by direct extension to neighboring organs and/or tissues or by metastasizing to distant sites by means of the vascular system (the blood stream), the lymphatic system, or by seeding or implantation of cancer cells in body cavities. Terms such as "mass" and "lump" are used to describe any overgrowth of tissue. However, these terms may not necessarily mean that such growths contain cancer cells. Types of Abnormal Cell GrowthIn addition to neoplasia, there are several other terms referring to abnormal cell growth. These include the following: Hyperplasia refers to an abnormal increase in the number of cells, which are in a normal component of that tissue and are arranged in a normal fashion with subsequent enlargement of the affected part. One example is thyroid hyperplasia, an enlargement of the thyroid gland caused by an abnormal rapid growth of the epithelial cells lining the follicles. Another example is: Guitar strumming leads to hyperplasia of the cells on the thumb (a callus is formed). The callus on the thumb is a hyperplastic growth. Hypertrophy refers to an abnormal increase in the size of each cell, for example, the increase in cell size of cardiac muscle. Metaplasia refers to the replacement of one mature cell type with another mature cell type: for example, squamous metaplasia of the respiratory columnar epithelium — as evidenced by the metaplastic cough of a smoker. Dysplasia refers to the replacement of one mature cell type with a less mature cell type: for example, dysplasia of the cervix epithelium. Hyperplasia, metaplasia, and dysplasia are reversible because they are results of a stimulus. Neoplasia is irreversible because it is autonomous. Tumor Terminology GeneralizationsNames of benign tumors usually end with "oma" regardless of their cell type. For example, a benign glandular tumor (epithelium tissue) is called adenoma and a benign bone tumor is called osteoma, while a malignant glandular tumor is called adenocarcinoma and a malignant bone tumor is called osteosarcoma. In addition to benign tumors, there are in situ tumors and invasive tumors. In situ tumors do not invade the basement membrane, whereas invasive tumors do invade the basement membrane. 
Tumors are abnormal masses of tissue formed when cells either grow too much or do not die when they should.1 Tumors are classified as one of two types – either benign (non-cancerous) or malignant (cancerous).2 In this article, we will describe what benign and malignant tumors are, explore the similarities and differences between the two types of tumors and discuss if benign tumors can become malignant. What is a tumor?Tumors are clusters of abnormal cells, and the word tumor comes from the Latin tumere – meaning “to swell”. The names of different types of tumors often end with the suffix “-oma”. Usually, cells divide and proliferate under tightly controlled conditions, balanced by the programmed death of cells (known as apoptosis). However, mutations can occur in cellular DNA that affect this balance. These mutations can be random or caused by specific factors such as tobacco smoking or exposure to radiation. If cells divide too much, or not enough cells undergo apoptosis, groups of cells can grow uncontrollably and produce a tumor. Tumors vary widely in size and can develop almost anywhere in the body. People often associate tumors with cancer. However, some tumors are cancerous (malignant) and others are non-cancerous (benign). But what is the difference between a benign and malignant tumor? What is a benign tumor?Benign tumors are non-cancerous and generally less harmful than malignant tumors. They can grow to large sizes – potentially causing pain and other problems by putting pressure on the area around the tumor – but do not invade other tissues or organs. They remain in their primary location, growing slowly and maintaining distinct borders around the edge of the tumor, and are unlikely to recur if they are surgically removed. There are many types of benign tumors, including:
What is a malignant tumor?Malignant tumors are cancerous, with the capacity to spread and establish new tumors in other tissues and organs in a process called metastasis. During metastasis, primary malignant tumors spread to secondary sites. Cancer cells break away from the tumor and spread via the blood or lymph system – commonly establishing metastases in the liver, lungs, brain and bones. Because of this, malignant tumors quickly require treatment to avoid spreading. Treatment usually entails surgical removal, chemotherapy, radiotherapy or a combination of these depending on how advanced the cancer is. There are several established characteristics or “hallmarks” of cancer, such as inducing the production of new blood vessels (angiogenesis) and sustaining growth-promoting cell signaling.8,9,10,11 There are many types of malignant tumors. CarcinomaCarcinomas develop in epithelial cells and are the most common type of cancerous tumor, representing 80–90% of cancers.12 Examples include:
SarcomaSarcomas develop from cells in connective tissues such as bone, cartilage, fat, muscle, tendons and ligaments. Examples include:
BlastomaThese are cancers in immature precursor cells known as “blasts”. These malignant tumors are more common in children and are also referred to as embryonal malignancies as they are thought to occur after genetic errors in fetal cell development.13 Each kind of blastoma is named according to its tissue of origin in the body. For example:
What’s the difference between benign and malignant tumors?The major difference between benign and malignant tumors is their ability to spread and invade other tissues. Benign tumors can grow to a large size, but do not expand into other tissues or other areas of the body. Malignant tumors, on the other hand, are more aggressive. These can invade neighboring tissues or even spread through the blood and lymph systems to distant parts of the body. New tumors that form in this way are called neoplasms, coming from the Greek “neo” meaning new, and “plasma” meaning formation. Figure 1: Graphic illustrating the differences in the morphology of benign and malignant tumors. The main differences between benign and malignant tumors are summarized in the table below:
Doctors can determine whether a tumor is benign or malignant by taking a biopsy – a small sample of the tumor tissue – to examine under the microscope. Can a benign tumor become malignant?In some cases, benign tumors can indeed become malignant. Benign tumors can develop into a third, intermediate type of tumor known as "pre-malignant" or "pre-cancerous". These growths remain benign but contain abnormal cells that have the potential to become cancerous in the future. One example of a pre-malignant tumor is known as carcinoma in situ.15 This is where abnormal cells are formed but have remained in place and not yet spread. However, they have the potential to spread into nearby tissue – for this reason, they are sometimes called “stage 0” cancer.16 Pre-malignant cells have several key characteristics that distinguish them from normal cells. These are:
One of the best examples of pre-malignant tumors are colon polyps – another name for small, abnormal growths. These polyps can be found during a colonoscopy (an examination using a camera to capture images of the inside of the colon). Some of these polyps have the potential to become pre-malignant and then malignant, requiring them to be closely monitored and possibly surgically removed. References:
Are benign tumor cells differentiated?Benign tumors have relatively well differentiated cells . They are often surrounded by an outer surface (fibrous sheath of connective tissue) or stay contained within the epithelium. Common examples of benign tumors include moles and uterine fibroids.
How do the cells of benign and malignant tumors differ?Some tumors are benign, which means they form in only one spot without spreading to surrounding tissue. Malignant tumors are cancerous and can spread to nearby tissue. As cancerous tumors grow, cancer cells can break off and travel throughout the body, forming new tumors.
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Benign tumors can often be differentiated from malignant tumors because benign tumors:
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