MicroBio 160 1st Edition Lecture 15 Outline of Last Lecture I Alcohol and Cancer II Alcohol Tobacco Synergistic III Signs and Symptoms IV 5 Year Survival Rates V Liver Cancer VI Staging VII Treatments Outline of Current Lecture I Skin Cancer Cases and Deaths II Risk Factors III Tanning Beds IV Skin Cancer and Exposure to Sunlight V Types of UV Radiation VI How UV damage leads to Cancer VII Types of Skin Cancer VIII Stages of Melanoma IX X Treating Skin Cancer BioVex Vaccine for Advanced Melanoma Current Lecture These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Skin cancer each people over 1 0 million people in the US find out that they have skin cancer it 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 and deaths from melanoma in the US in 2010 New cases 68 130 Deaths 8 700 Non melanoma new cases more than 1 000 000 deaths less than 1 000 Risk Factors for Skin Cancer Hereditary people with a family history of skin cancer are generally at a higher risk of developing the disease people with fair skin most susceptible Environment level of UV light Multiple nevi moles Occupational exposure to coal tar pitch creosote arsenic compounds or radium Elevation UV is stronger as elevation increases thinner at higher altitudes cannot filter UV Latitude rays of the sun are strongest near the equator Cloud cover places with regular cover may actually reduce UV Pigmentation and Risk Anyone can get skin cancer however people who have fair skin are at greater risk as well as people with red or blonde hair light colored eyes and freckles Melanosome an organelle containing melanin the most common light absorbing pigment found in the animal kingdom o Red melanosomes are much more reactive than black to oxidation it takes less of a trigger like 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 UVB are present in tanning booths o Doses of UVA and UVB can be up to 10x higher in one 5 minute session than sitting outside for 4 hours o You are 75x more likely to get melanoma Skin Cancer and Exposure to Sunlight People should avoid exposure to the midday sun from 10am to 3pm o UV rays come in contact with skin o Melanocytes produce melanin to protect the skin from UV rays o If UV rays exceed what can be blocked by your level of melanin sunburn results Types of Ultraviolet Radiation and their features Ultraviolet Radiation Type General Features Ultraviolet A Radiation UVA long wave UV 315400nm Ultraviolet B Radiation UVB sunburn radiation 280315nm Ultraviolet C Radiation UVC short wave UV 100280nm 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 Some filtered out in the atmosphere by the ozone layer Doesn t pass through glass Causes sunburn tanning wrinkling aging of the skin and skin cancer Highest intensity in the noon time 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 1000x more effective in causing sunburn Damages DNA Oxidize lipids and produces harmful free radicals Causes inflammation which also produces free radicals particularly nitrogen radicals Disrupts cell communication and causes expression of stress response genes Weakens the immune responses of the skin Effects of UV Radiation Origins of the Three Types of Skin Cancer Squamous Cell Cancer start in the middle layer of the epidermis usually affecting only the surrounding area but penetrating deeply into these tissues and gradually forming a raised patch with a rough surface Basal Cell Cancer originate in the lowest layer of the epidermis the cells invade and destroy surrounding tissues forming a painless bump or nodule that later becomes an open ulcer with a hard edge Malignant Melanoma the deadliest form of skin cancer occurs when pigment making cells in the basal layer called melanocytes begin reproducing uncontrollably to distant parts of the body Diagnosis Exam of the skin and lymph nodes Biopsy lesion o Shave punch incisional excisional only remove part of the tumor Mohs Surgery o Diagnostic and curative o Surgeon removes tumor by layers o Pathologist examines each layer for clear margins o Surgeon keep cutting until clear margins are attained Non invasive Melanoma Cancers usually non invasive and non metastatic Basal cell carcinoma 80 o 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 of the chest or back or on the back side of forearms or hands o Several nodules may merge together a nodule may ulcerate crust over or ooze fluid Squamous cell carcinoma 16 o Appears as a scaly reddish dome shaped fleshy nodule from 5mm to few cm if left untreated in size often with a central ulcer o Mostly appears on sun exposed areas of the skin or lips Incidence and Mortality Rates for Different Types of Skin Cancer Melanoma Arise from melanocytes and are more dangerous metastasize before tumor is noticed Melanomas account for only 4 of skin cancers but are responsible for the majority of fatalities 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 I melanoma is characterized by tumor thickness presence and number of mitoses a tumor 1mm and ulceration status There is no evidence of regional lymph node or distant metastasis o Stage IA no ulceration no mitoses o Stage IB ulceration and or mitoses Stage II melanoma is also characterized by tumor thickness and ulceration status There is no evidence of regional lymph node or distant metastasis Stage III melanoma is characterized by the level of lymph node metastasis There is no evidence of distant metastasis Stage IV melanoma is characterized by the location of distant metastases and the level of serum lactate dehydrogenase LDH o LDH is an enzyme found in the blood and many body tissues elevated LDH levels usually indicate the presence of
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