Carcinoma is a type of cancer that originates in the cells of epithelial tissue that line the inner or outer surfaces of the body whose DNA has become altered or damaged. This damage leads to transformation of the cells, which starts exhibiting abnormal malignant properties. Most cancers are carcinomas.

Cancer basics:

To understand what exactly carcinoma is, first we should understand cancer better.

Cancer in general needs no introduction. Cancer is not a single condition or disease. Rather, it is a group of more than a hundred distinct diseases. In simple words, cancer is the abnormal growth of cells in the body. There are control mechanisms in cells that restrict them from dividing abnormally.

Normally cells divide to replace old and worn out cells in a systematic way when they receive signals from neighboring cells. The old cells or worn out cells die and the new cells can replace them. A balance is always maintained in the body between the rate of cell death and cell growth. However, when cells in any part of the body start breaking free of all restrictions to divide, they can become cancer cells. Therefore, cancer cells are part of our body, but due to some damage, they lose the ability to stop obeying signals from other cells and continue dividing.

This misbehavior of cancer cells lead to the development of a mass of tissue called a tumor. Tumor is a Latin word which means swelling. There can be two different types of tumors in the body – benign and malignant. Benign tumors are non-cancerous and malignant tumors are cancerous.


Benign tumors are usually small and harmless and they do not spread to other parts of the body i.e. they cannot metastasize. Therefore, these tumors are not cancerous. These tumors can originate in any part of the body, but can be easily removed by surgery. They do not need to be removed unless they are causing symptoms or they need to be checked for malignancy.


Malignant tumors are very aggressive and rapidly growing. Unlike benign tumors, they can invade the other cells of the body so that they can spread rapidly. They break away from their site of origin, enter the blood stream, which gives them access to all parts of the body and results in new tumors. Therefore, they are cancerous. Carcinomas are a type of cancer; therefore all carcinomas are malignant.

The process of spreading of cancer cells or metastasis

Cancer cells have the ability to spread from their site of origin (primary tumor) to other tissues and organs, where they can form new secondary tumors. This process of spreading is called metastasis. The Greek word metastasis means displacement. Metastasis is one of the hallmarks of malignancy. The secondary tumor that arises due to metastasis is called metastases.

In order to metastasize, the malignant tumor cells break away from their site of origin and enter the circulatory system, which includes the cardiovascular system and lymphatic system. The cardiovascular system, through which blood flows, includes the blood vessels (arteries, veins and capillaries) and the heart. The lymphatic system plays a major role in body’s defense mechanism and acts as the secondary circulatory system. It carries lymph, a watery fluid containing white blood cells and plasma to all tissues of the body. Cancer cells after entering the blood stream can be carried easily to brain, liver, lungs, kidney and bones. When these cells reach the capillaries they can move through the wall of the blood vessels or the lymphatic vessels and infiltrate the tissues. The secondary tumor soon develops at the new site. The new tumor promotes the growth of new blood vessels (called angiogenesis) to obtain nutrients and oxygen.

Some cancer cells also penetrate and infiltrate surrounding normal tissues in the local area, without involving the circulatory system, forming masses near the original tumor. The degree of metastasis varies with the site of origin. Most malignant tumor cells metastasize, but there are exceptions. For example, basal carcinoma cells rarely spread from their site of origin or metastasize. Cells of secondary or metastatic tumors are similar to those in the original tumor. If, for example, liver cancer metastasizes to the lungs, the secondary tumor is formed of abnormal liver cells, not of abnormal lung cells. We say that the individual has metastatic liver cancer, not lung cancer. Cancers of the lymphatic system or the blood system are already a few steps ahead when it comes to metastasis.

The basic statistics on cancer:

The three most frequently occurring cancers, in accordance with the reports of National Cancer Institute in 2010, in the U.S. are as follows:

  • Men: Prostate, lung, and colorectal
  • Women: Breast, colorectal, and lung
  • Children: Leukemia, brain tumors, and lymphoma

The most common cause of deaths among patients with cancer depends on the type of cancer and the stage at which the disease has been detected. Several factors influence the incidence and types of cancer. People over 40 are susceptible to many forms of cancer. Therefore, age is critical. Some forms of cancer are more common in males and some in females. The incidence of some cancers is more in a particular race. Environment at work, lifestyle, and diet are some of the factors that can induce the development of cancer. There are cancers, which run in families. Therefore, genetics plays a major role in cancer, too. Lung, colon, and breast cancer account for the highest number of cancer deaths each year in the US..

Metastasis and genetics

The molecular mechanisms behind metastasis have received a lot of attention. The metastatic potential of cancer cells is dependent on differential expression of various genes. A number of genes have been shown to be involved in metastasis in different forms of cancer. Recently, researchers have used the DNA microarray technique to find that 32 among the 10,000 genes screened have a role in promoting metastasis. There are many more studies going on at present to find the genes involved in metastasis. Based on such findings, new therapeutic drugs can be designed to suppress the metastasis of tumors. Localized form of tumors are easy to treat and hence will increase the survival rate of the cancer patients.