The second most common behind basal cell carcinoma (BCC) which is up to 40 times more common
The sun’s rays damage skin cells making this the most common risk factor. Minimizing sun exposure is the best form of primary prevention of the development of SCC. It is far less common to encounter SCC in non-sun-exposed skin. Exposure to radiation, scarred areas or sites of chronic tissue trauma also lead to formation of SCC.
Besides sunlight, squamous cell carcinoma is greatly increased by long-term use of immunosuppressive drugs, particularly organ transplant patients. Squamous cell carcinoma is the most common cancer complicating immunosuppressive therapy.
Arsenic is found in soil and water and this chemical is a known carcinogen. It is sometimes used in glass manufacturing, pesticides, semiconductor production, pressure treated lumber and to preserve animal hides. Exposure is more likely to cause SCC in a palmoplantar distribution.
SCC may appear with a variety of presentations but in the skin often start out looking like an ulcer that does not heal or continues to grow, and frequently scales as a plaque.
Almost always in sun exposed areas like the head, neck and trunk this is a premalignant skin condition. It presents as rough, hyperkeratotic, pearly gray-white papules or plaques. Approximately 1 percent progress to SCC.
SCC tends to favor the lower lip, whereas basal cell carcinoma tends to favor the upper lip.
Histology will show abnormal squamous cells in concentric layers in a whorl pattern. It is also less often referred to as a “squamous eddy”.
This is the single most effective technique for removing basal and squamous cell carcinomas. Mohs micrographic surgery involves removing very thin slices of skin, immediately freezing them and examining the frozen sections for cancerous cells. This resecting, freezing and examining process continues, section by section, until the margin is cancer free. This process allows for loss of very little healthy tissue. It is best used on delicate areas of skin such as the nose, ears, eyelids, lips, hands, genitals, where maximal preservation of healthy tissue is critical for cosmetic or functional purposes.
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