Skin cancer

Skin cancer Microchapters
Patient Information
Overview
Historical Perspective
Classification Melanoma Basal cell carcinoma Squamous cell carcinoma of the skin Actinic keratosis Bowen's disease Keratoacanthoma Dermatofibrosarcoma protuberans Merkel cell carcinoma Kaposi's sarcoma Angiosarcoma Cutaneous B cell lymphoma Cutaneous T-cell lymphoma Sebaceous gland carcinoma
Pathophysiology
Causes
Epidemiology & Demographics
Risk factors
Screening
Diagnosis
Treatment
Prevention

Skin cancer
ICD-10	C43-C44
ICD-9	172, 173
ICD-O:	8010-8720
MeSH	D012878

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]Faizan Sheraz, M.D. [3]

Overview

Skin cancer is a malignant growth on the skin which can have many causes. Skin cancer generally develops in the epidermis (the outermost layer of skin), so a tumor is usually clearly visible. This makes most skin cancers detectable in the early stages. There are three common types of skin cancer, each of which is named after the type of skin cell from which it arises. Cancers caused by UV exposure may be prevented by avoiding exposure to sunlight or other UV sources, wearing sun-protective clothes, and using a broad-spectrum sun screen. Skin cancers are the fastest growing type of cancer in the United States. Skin cancer represents the most commonly diagnosed malignancy, surpassing lung, breast, colorectal and prostate cancer. More than 1 million Americans will be diagnosed with skin cancer in 2007.[1]

Classification

The most common types of skin cancer are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) which may be locally disfiguring but are unlikely to metastasize (spread to other parts of the body). The most dangerous type of skin cancer is malignant melanoma. This form of skin cancer can be fatal if not treated early but comprises only a small proportion of all skin cancers. More rare types of skin cancer include: • Dermatofibrosarcoma protuberans • Merkel cell carcinoma • Kaposi's sarcoma

Pathophysiology

Macroscopically, the tumor is often elevated, fungating, or may be ulcerated with irregular borders. Microscopically, tumor cells destroy the basement membraneand form sheets or compact masses which invade the subjacent connective tissue (dermis). In well differentiated carcinomas, tumor cells are pleomorphic/atypical, but resembling normal keratinocytes from prickle layer (large, polygonal, with abundant eosinophilic (pink) cytoplasm and central nucleus). Their disposal tends to be similar to that of normal epidermis: immature/basal cells at the periphery, becoming more mature to the centre of the tumor masses. Tumor cells transform into keratinized squamous cells and form round nodules with concentric, laminated layers, called "cell nests" or "epithelial/keratinous pearls". The surrounding stroma is reduced and contains inflammatory infiltrate (lymphocytes). Poorly differentiated squamous carcinomas contain more pleomorphic cells and no keratinization.[1]

Epidemiology & Demographics

• Skin cancer is an increasingly common condition. This is in part attributed to increased exposure to ultraviolet radiation, which in turn is thought to be caused by the increased popularity of sun tanning (sun bathing). Lighter-skinned individuals are more vulnerable. In the United States, about one out of every three new cancers arises from the skin.

Risk factors

Skin cancer is most closely associated with chronic inflammation of the skin. This includes: 1. Sunburn or excessive sun damage, especially early in life. UVA & UVB have both been implicated in causing DNA damage resulting in cancer. Sun exposure between 10AM and 4PM is thought to be most harmful. Natural (sun) & artificial UV exposure (tanning salons) are associated with skin cancer. 2. Chronic non-healing wounds, especially burns. These are called Marjolin's ulcers based on their appearance and can develop into squamous cell carcinomaand. 3. Genetic predisposition, including "Congenital Melanocytic Nevi Syndrome". CMNS is characterized by the presence of "nevi" or moles of varying size that either appear at or within 6 months of birth. Nevi larger than 20 mm (3/4") in size are at higher risk for becoming cancerous. Skin can be protected by avoiding sunlight entirely, or wearing protective clothing while outdoors. Skin cancer is usually caused by exposing skin to UV rays excessively. There are a variety of different skin cancer symptoms. These include crabs or changes in the skin that do not heal, ulcers in the skin, discoloration, and changes in existing moles.

Diagnosis

Skin cancer physical examination|Physical Examination

• Basal cell carcinoma usually looks like a raised, smooth, pearly bump on the sun-exposed skin of the head, neck or shoulders. Sometimes small blood vesselscan be seen within the tumor. Crusting and bleeding in the center of the tumor frequently develops. It is often mistaken for a sore that does not heal. • Squamous cell carcinoma is commonly a red, scaling, thickened patch on sun-exposed skin. Ulceration and bleeding may occur. When SCC is not treated, it may develop into a large mass. • Most melanomas are brown to black looking lesions. Signs that might indicate a malignant melanoma include change in size, shape, color or elevation of a mole. The appearance of a new mole during adulthood, or new pain, itching, ulceration or bleeding of an existing mole should be checked. The following image is an example of how skin cancer can affect the nails. Image shown below is courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology • Skin carcinoma

Treatment

Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

Case Studies

Case #1

Related Chapters

• Cancer
• Mohs surgery

References

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