Lecture 21 Skin Cancer Skin Cancer Each year over 1 0 million people in the U S find out that they have skin cancer Estimated new cases and deaths from melanoma in the U S in 2015 New cases 73 870 Deaths 9 940 Non Melonoma New cases more than 1 000 000 Deaths Less than 1 000 What are Risk Factors for Skin Cancer Heredity People with a family history of skin cancer are generally at a higher risk of developing the disease People with fair skin and a northern European heritage appear to be most susceptible Environment Level of UV light today is higher than it was 50 or 100 years ago Ozone serves as a filter to screen out and reduce the amount of UV light that we are exposed to With less atmospheric ozone a higher level of UV light reaches the earth s surface Multiple Nevi moles or atypical nevi Occupational exposure to coal tar pitch creosote arsenic compounds or radium Elevation UV is stronger as elevation increases because the thinner atmosphere at higher altitudes cannot filter UV as effectively as it does at sea level Cloud cover Places with regular cloud cover may actually reduce UV resulting in a 50 percent lower level of UV light Pigmentation and Risk Although anyone can get skin cancer the people who have fair skin are at a greater risk Skin that freckles easily and people with red or blond hair and blue or light colored eyes are at a higher risk of skin cancer A melanosome is an organelle containing melanin the most common light absorbing pigment found in the animal kingdom Red melanosomes are much more reactive than the black melanosomes to oxidation It takes less of a trigger namely UV rays in sunlight to make potentially harmful cellular changes in people with red hair Tanning Beds and Cancer Risk The World Health Organization moved UV tanning beds to its highest cancer risk category carcinogenic to humans UVA and 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 Skin Cancer and Exposure to Sunlight Whenever possible people should avoid exposure to the midday sun from 10am to 3pm Keep in mind that protective clothing such as sun hats and long sleeves can block out the sun s harmful rays If UV rays exceed what can be blocked by your level of melanin sunburn results Types of Ultraviolet Radiation and their Features Ultraviolet A Not filtered out in the atmosphere Passes through glass Produces some tanning Once considered harmless but now believed harmful over the long term Levels remain relatively constant throughout the day Ultraviolet B Some filtered out in the atmosphere by the ozone layer Does not pass through glass Causes sunburn tanning wrinkling aging of the skin and skin cancer Highest intensity at noontime Ultraviolet C Filtered out in the atmosphere by the ozone layer before reaching earth Major artificial sources are germicidal lamps Burns the skin and causes skin cancer How UV Damage Leads to Cancer UVB is the main cause of skin cancer also 1000 times more effective in causing sunburn radicals Damages DNA Oxidize lipids and produces harmful free radicals Causes inflammation which also produces free radicals particularly nitrogen Disrupts cell communication and causes expression of stress response genes Weakens the immune responses of the skin Effects of UV Radiation Seeking Stability Atoms form molecules share electrons to maintain equal pairs Stable Atom Equal pairs of protons electrons How Free Radical Forms Antioxidants in body neutralize free radicals Stopping the Damage Antioxidants donate an electron chain reaction ends Antioxidants May Make Cancer Worse Origin of The Three Types of Skin Cancer 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 Dells invade and destroy surrounding tissues Forms a painless bump that becomes an open ulcer with hard edge Malignant Melanoma Most deadly Starts with non controlled growth of melanocytes pigment making cells in basal layer Spreads to other parts of body Exam of skin and lymph nodes Biopsy lesion Diagnosis Shave Punch Incisional 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 Two major types usually non invasive and non metastic 1 Basal Cell Carcinoma 80 2 Squamous Cell Carcinoma 16 Basal and Squamous Cell Carcinomas Squamous Cell Carcinoma Appears as a scaly reddish dome shaped fleshy nodule from mm to few cm if left untreated in size often with a central ulcer Mostly appears on sun exposed areas of the skin or lips Basal Cell Carcinoma Pearl like greyish nodule few mm in size appears mostly on the sun exposed areas of the face including the lips scalp neck upper area o the check or back or on the back side of forearms or hands Several nodules may merge together A nodule may ulcerate crush over or ooze fluid Incidence and Mortality Rates for Different Types of Skin Cancer Basal Cell Carcinoma 1 3 million cancer cases Melanoma 10 000 cancer cases Melanomas arise from melanocytes and are more dangerous metastasize before Melanomas account for only 4 of skin cancers but are responsible for the tumor is noticed majority of fatalities Melanoma Melanoma Incidence of melanoma has risen 3 each year for 30 years Only preventable cancer that has not had decline in mortality rates Melanoma is one of the most common cancers in young adults mostly women Stages of Melanoma Stage 0 Melanoma involves the epidermis but has not reached the underlying dermis This stage is also called melanoma in situ Stage 1 Melanoma is characterized by tumor thickness presence and number mitosis a tumor 1mm and ulceration status There is no evidence of regional lymph node or distant metastasis Stage 1A no ulceration no mitosis Stage 1B Ulceration and or mitosis Stage 2 Melanoma is also characterized by tumor thickness and ulceration status There is no evidence of regional lymph node or distant metastasis Stage 3 Melanoma is characterized by the level of lymph node metastasis There is no evidence of dustant metastasis Stage 4 Melanoma is characterized by the location of distant metastasis and the level of serum lactate dehydrogenase LDH LDH is an enzyme found in the blood and many body tissues Elevated LDH levels usually indicate the presence
View Full Document
Unlocking...