Skin cancer Skin cancer is the most common type of cancer in the US 40 50 of Americans who live to age 65 have skin cancer at least once Estimated new cases 73 870 and deaths 9 940 from melanoma Risk factors Environment level of US light today is higher than it was 50 or 100 years ago Heredity people with high history of skin cancer higher risk of developing the disease Multiple nevi moles or atypical nevi Occupational exposure to coal car pitch creosote arsenic compounds or radium Elevation UV is stronger as elevation increases Latitude the rays of the sun are strongest near the equator Cloud cover places with regular cloud cover may actually reduce UV Pigmentation and risk Melanosome is an organelle containing melanin light absorbing pigment Read melanosomes are much more reactive than the black melanosomes to oxidation The people who have fair skin skin that freckles easily and people with red or blond hair and blue or light colored eyes are at higher risk of skin cancer Tanning beds Tanning beds highest cancer risk category carcinogenic to humans UVA UVB are present in tanning booths Doses of UVA and UVB can be up to 10x higher in one 5 minute session than sitting outside for 4 hours 75x more likely to get melanoma Exposure to sunlight whenever possible people should avoid exposude to midday sun from 10am to 3pm keep protective clothing on such as sun hats and long sleeves melanocytes produce melanin to protect the skin from UV rays if UV rays exceed what can be blocked by your levels of melanin sunburn results How UV damage cancer UVB is main cause of skin cancer Damages DNA Oxidize lipids and produces harmful free radials Disrupts cell communication and causes expression of stress response genes Weakens the immune responses of the skin Causes inflammation which also produces free radicals particularly nitrogen radicals Effects of UV radiation Antioxidants might prevent DNA damage and impede tumor initiation But once cancer starts it might help facilitate and feed it 3 types of cancer cells Squamous cell cancer starts in middle layer of epidermis and penetrating deeply gradually forms a raised patch with rough surface Basal cell cancer originate in lowest layer of epidermis Cells invade and destroy surrounding tissue forms a painless bump that becomes an open ulcer with hard edge Malignant melanoma most deadly starts with uncontrolled growth of melanocytes spreads to other parts of the body Diagnosis Exam of skin and lymph nodes Biopsy lesion shave punch incisional these 3 only remove part of the tumor excisional Mohs surgery diagnostic and curative surgeon removes tumor by layers pathologist examines each layer for clear margins surgeon keeps cutting until clear margins are attained Non melanoma cancers 2 major types non invasive and non metastatic basal cell carcinoma 80 pearl like greyish nodule appears mostly on sun exposed areas of the face scalp neck upper area of chest or back several nodules may merge together a nodule may ulcerate crust over or ooze fluid squamous cell carcinoma 16 appears as a scaly reddish dome shaped fleshy nodule mostly appears on sun exposed areas of skin or lips arise from melanocytes dangerous because it metastasizes before tumor is noticed account for only 4 of skin cancers but responsible for the majority of fatalities Melanoma Stages of Melanoma Stage 0 involves the epidermis but has not reached the underlying dermis Stage also called melanoma in situ Stage 1 tumor thickness presence and number of mitoses tumor smaller than 1mm and ulceration status No evidence of regional lymph node or distant metastasis Stage 1A no ulceration no mitoses 5 yr survival rate 97 Stage 1B ulceration and or mitoses 5 yr survival rate 92 Stage 2 characterized by tumor thickness and ulceration status No evidence of regional lymph node or distant metastasis Stage 3 characterized by level of lymph node metastatis but no evidence of distant metastasis Stage 4 melanoma is characterized by location of distant metastases and level of serum lactate dehydrogenase LDH LDH is an enzyme found in the blood and many body tissues Elevated levels of LDH indicates presence of metastatic disease Treating skin cancer
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