Melanoma is a type of highly invasive skin cancer. It is the most dangerous and most frequently heard of cancer of the skin. However, there are many other types of skin cancers, as well. This article will outline the causes, clinical features, symptoms, investigation and diagnosis, prognosis, and treatment of skin cancers, especially of melanoma.
Melanoma
Melanoma is a highly invasive carcinoma. It is an uncontrollable overgrowth of melanocytes. Melanocytes are responsible for producing skin pigments. Therefore, melanoma can arise from any part of the body where there are melanocytes. In the UK, 3500 new cases are identified per year. 800 people have died only during the last 20 years. Melanoma is commoner among Caucasians. It is commoner in females.
All cancers arise because of an irreparable alteration of skin cell DNA. Sunlight is a major cause of melanoma, especially in early years. Diagnosis of melanoma is tricky. There is a checklist, made in Glasgow, to ensure that no cases are missed. Malignant melanoma may change its size, shape and color. There may also be inflammation, crusting, bleeding and sensory changes. Neighboring satellite lesions can appear, but if they are well demarcated, smooth, and regular, it is unlikely to be a melanoma. Melanoma can be subdivide into lentigo maligna, lentigo maligna melanoma, superficial spreading, acral, mucosa, nodular, polypoid, desmoplastic, and amelonatic melanoma. Although many melanomas conform to these basic rules, nodular melanomas do not. They are elevated, firm nodules, which are rapidly growing. Serum lactate dehydrogenase level rises when there is metastatic spread. CT, MRI, sentinel lymph node biopsies, and skin lesion biopsies may play a role in confirmation of diagnosis. After confirmation, a wide excision of the tumor may be performed. Involved may be removed surgically. According to spread, adjuvant immunotherapy, chemotherapy and radiotherapy may be needed. Chemotherapy, immunotherapy, and radiotherapy may be given if the cancer is systemically or locally advanced.
Prevention of exposure to UV light is thought to be preventive of melanoma. As a rule of thumb, avoiding sun exposure between 9 am and 3 pm is a good method. Sun creams and other preparations may help, but there is a risk of allergies and other skin changes with the use of these applications. Less invasive melanomas with lymph node spread have a better prognosis than deep melanomas without lymph node spread. When melanoma is spread to lymph node, the number of involved nodes is related to prognosis. Widely metastatic melanoma is said to be incurable. Patients tend to survive 6 to 12 months after diagnosis.
Skin Cancers
Skin tumors are abnormal growths of skin cells. These can be divided into two categories. They are benign and malignant. Benign tumors are slow growing masses of tissue that will not spread to other places or invade surrounding structures. Malignant tumors invade surrounding structure as well as spread to distant locations via blood and lymph. These distant sites containing fragments of cancer are called metastatic sites. Liver, kidneys, prostate, vertebral column, and brain are a few well known sites where cancer spreads.
Sunlight causes cancer, especially with prolonged exposure. Ultra violet light, tobacco, human papillomavirus, ionizing radiation, low immunity and congenital conditions like congenital melanocytic nevi syndrome are some of the known causes of skin cancer.
Skin consists of multiple layers of cells. The bottom most layer is the actively dividing basal cell layer. This layer is the most susceptible to malignant changes. Basal cell cancers are the commonest type of skin cancer. However, they are less invasive than malignant melanoma. The superficial layers are made up of progressively flat cells called squamous cells. These cells acquire keratin as they travel to the outer surface of the skin from the deeper layers. These cells can also undergo malignant transformation and give rise to squamous cell carcinomas. These are less common than basal cell carcinomas. They metastasize more frequently than basal cell cancers. Interspersed between the basal cells in the deepest layer of the skin are melanocytes. These are the pigment cells of the skin. When these cells undergo malignant transformation, melanomas arise. These are highly invasive cancers.
Layers of the skin, Author: Don Bliss, National Cancer Institute
Basal cell cancers are commonly seen in sun exposed areas of skin. They present as pearly, pale, smooth and raised patches. Head, neck, shoulders and arms are mostly affected. There is telangiectasia (small dilated blood vessels within the tumor). There may be bleeding and crusting giving an impression of a non-healing ulcer. Basal cell cancers are the least deadly of all skin cancers, and it is completely curable with proper treatment.
Squamous cell cancers present as red, scaly, thickenings of skin. If untreated they may reach an alarming size. They are dangerous but not so much as melanomas.
Malignant melanomas present as large, asymmetrical, evolving patches with varying color and irregular margin. Malignant melanomas metastasize rapidly and are extremely deadly.
Treatment for skin cancers depends on age, stage, spread, and recurrence. Type of cancer also affects the treatment decisions. Chemotherapy and radiotherapy are effective against basal cell carcinoma and squamous cell carcinoma. Melanoma is resistant to radiation and chemotherapy. Micrographic surgery is a method where the cancer is removed with the minimum amount of surrounding tissue.
Melanoma is deadlier than basal cell carcinoma and squamous cell carcinoma. Melanoma is less common that other two cancers. Melanoma spread more than other two types.
Read more:
1. Difference Between Mole and Skin Cancer
2. Difference Between Brain Tumor and Brain Cancer