Cancer is the second leading cause of death in the United States. It is a term given to a series of diseases in which the cells within human body grow at an abnormal rate, thereby damaging healthy tissues . While normal cells grow and die at a specific rate according to the requirements of human body, the growth of cells is extreme when compared to the death of cells in cancerous patients. Such an abnormal growth in turn leads to tumors, which consist of a huge mass of tissues. However, in patients suffering with cancer related to the blood, there is no or least possibility of solid tumors. Cancer cells are malignant in nature, which means that they easily spread from one tissue to another tissue either through the blood or lymphatic system . Cancer is caused by certain changes in the genes that control the growth and division of cells. The disease is either hereditary or occurs as a result of environmental exposure, which alters the DNA of individuals. Environmental exposure includes tobacco usage, exposure to sun’s radiation and many others.
While there are over 100 distinct types of cancer, this paper discusses about one of the most common types of cancer known as melanoma or skin cancer . Skin cancer occurs in the outer layer of the skin’s surface, which contains several types of cells known as melanocytes, basal cells and squamous cells. Some of the common signs and symptoms of skin cancer include unusual sores, moles and lumps on the skin, including blemishes and abnormal changes. Normal moles appear at birth, in childhood and adulthood, and do not vary in size or shape during the later years . However, in cancerous patients, moles are irregular and blurred. They occur in different shades and usually do not match one another. Furthermore, while normal moles are less than 6 millimeters in diameter, cancer moles are relatively larger in size. Sores that do not heal, pigments that spread rapidly, swellings, tenderness, pain and scaliness on the skin are usual symptoms of skin cancer .
According to the 2015 statistics reported by the American Cancer Society, 76,380 new skin cancer cases have been diagnosed and 10,130 patients suffering from skin cancer are expected to die of the disease . The occurrence of skin cancer in Whites is 20 times more when compared to other ethnicities. The risk of skin cancer increases with age and peaks over 60 years, while it is not uncommon in individuals below 30 years of age. One of the most common risk factors of skin cancer includes over exposure to sun, especially ultraviolet rays . Ultraviolet rays cause harm and alter the DNA of the skin, thereby affecting the genes that control the growth of skin cells. Frequent sunburns and constant exposure to sun during the peak hours, such as 10 am to 4 pm, including usage of sun lamps and tanning beds increase the chances of occurrence of skin cancer. Skin cancer usually develops in sun-exposed areas of the skin, such as arms, legs, face and neck, although it is uncommon in palms, soles and mouth . Individuals having more number of moles are likely to encounter skin cancer at some point in their life. Individuals with weakened immune systems also have the possibility of skin cancer as their body fails to fight against cancer-causing cells. In the US, men over the age of 45 years have a higher rate of occurrence of skin cancer when compared to women.
Genes play an important role in the prevalence of skin cancer. Most of the skin cancers begin when certain genes in a particular cell undergo mutation to create abnormal proteins either by nature or by environmental exposure . Individuals born with mutated genes are likely to pass on cancers from one generation to another generation when compared to those acquiring cancer as a result of environmental changes. The risk of skin cancer is twice or thrice higher in individuals whose first-degree relatives, such as parents and siblings are diagnosed with the disease. Some of the common inherited genes responsible for the occurrence of skin cancer include CDKN2A, MDm2, CDK4, RB1, MC1R and TYR. CDKN2A gene regulates cell division, while MDm2 gene suppresses tumors . Mutations in these two genes increase the likelihood of skin cancer as the cells fail to control cell growth and tumors. The other genes mentioned above indirectly impact the growth and division of cells, thereby impacting the susceptibility to skin cancer. On the other hand, non-inherited genes responsible for the occurrence of skin cancer include BRAF, EGF, PTEN and Fas . While BRAF increases the onset of skin pigments, EGF regulates the growth of epidermis or outer layer of the skin. Mutations occurring in these two genes are responsible for the occurrence of skin cancer. Fas gene is responsible for the self-destruction of skin cells. Fas gene mutations fail to control the destruction of cells, thereby resulting in their abnormality . Mutations in PTEN gene fails to control the progression of cell-cycle and leads to rapid spread of skin cancer.
The diagnosis of skin cancer involves a clear examination of skin abnormalities, such as the size, shape and texture of moles and lumps on the skin. There are certain tests that determine whether or not an individual has skin cancer, which include dermatoscopy or surface microscopy . In case the dermatologist suspects skin cancer, the diagnosis might include a skin biopsy, in which the sample collected from the skin determines the presence of cancerous cells. Skin biopsy consists of different types, such as shave biopsy, punch biopsy and incisional biopsy . Shave biopsy requires shaving off the top layer of the skin, while punch biopsy requires removing the edges of the skin until the subcutis layer. On the other hand, incisional biopsy involves a surgical procedure to remove a portion or entire skin tumor for examination. Other common tests conducted for the identification of skin cancer include immunohistochemistry, comparative genomic hybridization, lactate dehydrogenase and fluorescence in situ hybridization . Imaging tests and CT scan are also significant laboratory tests that determine the presence of skin cancer.
Distinct types of treatment are available for skin cancer. However, the primary treatment option is preferably a surgery. The decision of whether or not to perform a surgery depends on various factors, such as size, location, type and stage of skin cancer. While skin cancers occurring in the basal cells can be removed using a general surgical procedure through the use of a local anesthetic, severe cancers require surgery under a general anesthetic . Radiotherapy is also an efficient procedure for effective treatment of skin cancer. It is a preferred method if cancer covers a larger area of the skin or if it is present at a location that is hard to operate . In patients who are unsuitable for surgery, such as the elderly and patients with other health problems, radiotherapy helps to treat skin cancer. Chemotherapy is another available method of treatment for skin cancer. In chemotherapy, injections, ointments and tablets are administered locally for cancers present on the top layers of the skin . In some patients, doctors prefer immunotherapy, in which the administration of Interferon helps to stimulate the immune system, thereby enabling it to effectively identify and destroy cancer cells. Photodynamic therapy is a relatively new treatment available for skin cancer and is considered an alternative to surgery. This therapy involves administration of drugs to make cancer cells subtle to a specific type of light, which helps in destroying them . In patients who require multiple surgeries, photodynamic therapy is a better option. However, it is not suitable if cancer is present in the deeper layers of the skin.
In recent years, scientists have made considerable progress to understand the damage caused to DNA through ultraviolet (UV) rays. This has helped them to discover new strategies for the treatment and prevention of skin cancer. Since radiotherapy and chemotherapy are hard to treat skin cancer, scientists have been conducting trials on newer drugs, which target advanced cancer occurring in the squamous cells . New therapies and drugs have been targeted on a protein called EGFR. Excess amount of EGFR on the surface of the skin increases the growth of cancer cells. Hence, new drugs, such as gefitinib, erlotinib and cetuximab are undergoing clinical trials to find an effective treatment for skin cancer . Another drug targeting distinct proteins leading to skin cancer, such as dasatinib is also in the clinical trial process and expected to be in the market soon. While the possibility of basal cell skin cancers reaching advanced stages is rare, they are difficult to treat. Therefore, scientists are looking towards sonidegib and vismodegib as they target the signaling pathways in cancer cells .
References
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