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

• Skin cancer is broadly divided into melanoma and nonmelanoma types as shown in the following table:

Classification of skin cancer

Skin cancer type	Characteristics
Malignant melanoma	Most dangerous type of skin cancer Fatal if not treated early Comprises only a small portion of all skin cancers	Most common type
Nonmelanoma skin cancers
Basal cell carcinoma (BCC)		Most common types
Squamous cell carcinoma (SCC)	Local disfiguration Unlikely to metastasize
Dermatofibrosarcoma protuberans		Rare types
Merkel cell carcinoma
Kaposi's sarcoma
Angiosarcoma
Cutaneous B-cell lymphoma
Cutaneous T-cell lymphoma
Sebaceous gland carcinoma

Pathophysiology

Skin cancer is most closely associated with chronic inflammation of the skin.UVA & UVB have both been implicated in causing DNA damage resulting in cancer 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.

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

Common risk factors for skin cancer include:

Risk factors for the development of skin cancer

Risk factors	Associated features
Excessive sun exposure	Especially early in life can lead to skin damage and even sunburn Sun exposure between 10AM and 4PM is considered to be most harmful
Artificial UV exposure	Tanning salons
Fair skin	Less melanin pigment in the skin means less protection from damaging UV radiation
Genetic predisposition	Congenital Melanocytic Nevi Syndrome is characterized by: Presence of varying sized "nevi" or moles Appear at or within 6 months of birth Nevi larger than 20 mm (3/4") in size are at higher risk for becoming cancerous
Chronic non-healing wounds	Especially burns, known as Marjolin's ulcers (can transform into squamous cell carcinoma)
Prior history of sunburns
High altitude or sunny climate
Prior chemotherapy
Moles
Advanced age	Age >70 years
Precancerous skin lesions
Radiation exposure	Prior history of radiation therapy for skin conditions such as: Acne Eczema
Personal history of skin cancer
Exposure to certain substances	Arsenic
Family history of skin cancer
Weakened immune system	Due to: HIV infection (AIDS) Taking immunosuppressant therapy after organ transplantation
Male gender

Diagnosis

History and Symptoms

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.

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

Treatment

For low-risk disease, radiation therapy and cryotherapy (freezing the cancer off) can provide adequate control of the disease; both, however, have lower overall cure rates than surgery. Moh's Microsurgery is a technique used to remove the cancer with the least amount of surrounding tissue and the edges are checked immediately to see if tumor is found. This provides the opportunity to remove the least amount of tissue and provide the best cosmetically favorable results. This is especially important for areas where excess skin is limited, such as the face. Cure rates are equivalent to wide excision. Special training is required to perform this technique. In the case of disease that has spread (metastasized) further surgical or chemotherapy may be required.[1]

Prevention

Although it is impossible to completely eliminate the possibility of skin cancer, the risk of developing such a cancer can be reduced significantly with the following steps: • Reducing exposure to ultraviolet (UV) radiation, especially in early years • Avoiding sunburns • Avoiding sun exposure during the day (usually from 10 AM to 3 PM), when the sun is highest in the sky • Wearing protective clothing (long sleeves and hats) when outdoors • Using a broad-spectrum sunscreen that blocks both UVA and UVB radiation • Use SPF sun block of at least 50 • Reapply sun block every 2 hours and after swimming Although it is generally accepted that UV exposure is the greatest risk factor in melanoma development, some skeptics say that there is no proven data that links moderate sun exposure with the appearance of melanoma.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.

Related Chapters

• Cancer
• Mohs surgery

References

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