Melanoma

What is melanoma?

Melanoma is a type of skin cancer. It begins in certain cells in the skin called melanocytes. Each year more than 53,600 people in the United States find out they have melanoma. To understand melanoma, it is helpful to know about the skin and about melanocytes, what they do, how they grow, and what happens when they become cancerous.

THE SKIN

The skin is the body's largest organ. It protects us against sunlight, injury, and infection. It helps regulate body temperature, stores water and fat, and produces vitamin D. The skin has two main layers: the outer epidermis and the inner dermis.

The epidermis is mostly made up of flat, scalelike cells called squamous cells. Round cells called basal cells lie under the squamous cells in the epidermis. The lower part of the epidermis also contains melanocytes.

The dermis contains blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands produce sweat, which help regulate body temperature, and some produce sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin's surface through tiny openings called pores.

Healthy cells that make up the skin normally grow, divide, and replace themselves in an orderly way as the body needs them. This helps keep the skin in good repair.

MELANOCYTES AND MOLES

Melanocytes are spread throughout the lower part of the epidermis. They produce melanin, the pigment that gives our skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

Sometimes, melanocytes grow in a cluster. Benign (not cancerous) clusters of melanocytes are called moles. (Doctors also call a mole a nevus; the plural is nevi). Moles are very common. Most people have between 10 and 40 of these brown, tan, or black areas on the skin. Moles can be flat or raised. They are usually round or oval and smaller than a pencil eraser. They can be present at birth or appear later, usually before age 40. Moles generally grow or change only slightly over a long period of time. They tend to fade away in older people. When moles are surgically removed, they normally do not return.

CANCER

Cancer is a group of diseases with one thing in common: cells become abnormal, dividing too often and without control or order. These malignant (cancerous) cells form a tumor and can invade and destroy nearby tissue. The cancer cells can also spread through the lymphatic system or the bloodstream to other parts of the body and form new tumors. The spread of cancer is called metastasis




MELANOMA



Melanoma occurs when melanocytes become malignant. The disease is also referred to as cutaneous melanoma or malignant melanoma. (Another type of melanoma, ocular melanoma, develops in the eye and is not discussed here).
Melanoma can occur on any skin surface. In men, it is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the lower legs or the trunk. Melanoma is rare in black people and others with dark skin. When it does develop in dark-skinned people, it tends to occur under the fingernails or toenails, or on the palms or soles. Melanoma affects people of all age groups, but the chance of developing this disease increases with age.

Brain Tumor

What is the brain?

Together, the brain and spinal cord form the central nervous system. This complex system is part of everything we do. It controls the things we choose to do,like walk and talk,and the things our body does automatically,like breathe and digest food. The central nervous system is also involved with our senses; seeing, hearing, touching, tasting, and smelling, as well as our emotions, thoughts, and memory.

The brain is a soft, spongy mass of nerve cells and supportive tissue. It has three major parts: the cerebrum, the cerebellum, and the brain stem. The parts work together, but each has special functions.

The cerebrum, the largest part of the brain, fills most of the upper skull. It has two halves called the left and right cerebral hemispheres. The cerebrum uses information from our senses to tell us what is going on around us and tells our body how to respond. The right hemisphere controls the muscles on the left side of the body, and the left hemisphere controls the muscles on the right side of the body. This part of the brain also controls speech and emotions as well as reading, thinking, and learning.

The cerebellum, under the cerebrum at the back of the brain, controls balance and complex actions like walking and talking.

The brain stem connects the brain with the spinal cord. It controls hunger and thirst and some of the most basic body function, such as body temperature, blood pressure, and breathing.

The brain is protected by the bones of the skull and by a covering of three thin membranes called meninges. The brain is also cushioned and protected by cerebrospinal fluid. This watery fluid is produced by special cells in the four hollow spaces in the brain, called ventricles. It flows through the ventricles and in spaces between the meninges. Cerebrospinal fluid also brings nutrients from the blood to the brain and removes waste products from the brain.

The spinal cord is made up of bundles of nerve fibers. It runs down from the brain through a canal in the center of the bones of the spine. These bones protect the spinal cord. Like the brain, the spinal cord is covered by the meninges and cushioned by brospinal fluid.

Spinal nerves connect the brain with the nerves in most parts of the body. Other nerves go directly from the brain to the eyes, ears, and other parts of the head. This network of nerves carries messages back and forth between the brain and the rest of the body.

What are brain tumors?

The body is made up of many types of cells. Each type of cell has special functions. Most cells in the body grow and then divide in an orderly way to form new cells as they are needed to keep the body healthy and working properly. When cells lose the ability to control their growth, they divide too often and without any order. The extra cells form a mass of tissue called a tumor. Each year, more than 16,000 people find out they have a brain tumor. Tumors are benign or malignant.

Benign brain tumors do not contain cancer cells. Usually these tumors can be removed, and they are not likely to recur. Benign brain tumors have clear borders. Although they do not invade nearby tissue, they can press on sensitive areas of the brain and cause symptoms.

Malignant brain tumors contain cancer cells. They interfere with vital functions and are life-threatening. Malignant brain tumors are likely to grow rapidly and crowd or invade the tissue around them. Like a plant, these tumors may put out "roots" that grow into healthy brain tissue. If a malignant tumor remains compact and does not have roots, it is said to be encapsulated. When an otherwise benign tumor is located in a vital area of the brain and interferes with vital functions, it may be considered malignant (even though it contains no cancer cells).

Doctors refer to some brain tumors by grade - from low grade (grade I) to high grade (grade IV). The grade of a tumor refers to the way the cells look under a microscope. Cells from higher grade tumors are more abnormal looking and generally grow faster than cells from lower grade tumors; higher grade tumors are more malignant than lower grade tumors.