Squamous cell carcinoma in situ/Bowen's disease

Squamous cell carcinoma in situ/Bowen's disease

Chris Schach

Author Bio -

 Key Points
*Common skin cancer, forming in the cells of the outer skin layer
*Most cases caused by sun exposure, but may be the result of other factors
*Consists of scaly, crusted lesions which are tender and slow-growing and may ulcerate

Squamous cell carcinoma (SCC) is a common skin cancer, which forms in the squamous cells, which make up the outer layer of skin. The condition typically presents in areas exposed to sun, such as the face, lips, ears hands, arms, and lower legs, though it may develop in other areas. It  sometimes develops on mucosal surfaces such as the genitals or mouth.  Lesions typically present as a scaly, crusted bumps or flat red or pink scaly spots, which may be tender and usually slow growing. They sometimes sting or burn or feel like a thorn is pricking the skin.  Lesions may develop sores and ulcerate.  Size of these cancers may be anywhere from very small to centimeters in diameter.When it is confined to the outer skin layer (the epidermis), it is called squamous cell carcinoma, in situ.  In situ is latin for 'in place' which describes the superficial growth pattern of this early squamous cell carcinoma.  If an SCC, in situ, is not treated, it will eventually invade.  SCCs which are invasive spread to deeper skin layers.  In a small percentage of cases, SCCs may metastasize, most often when located on the lip, ear, back of the hand, forehead or scalp.  In immunocompromsed patients, SCC's tend to be more aggressive in their growth and are at greater risk for metastasis.  

SCC is most often caused by excessive sun exposure. Other factors which may increase the likelihood of developing the condition include: family history, smoking, large burns, persistent ulcers, long-term use of immunosuppressants, and infection with a strain of human papillomavirus (which causes most genital SCCs). Any person previously treated for the condition is at increased risk as well. Anyone may be affected by the condition, but those with the fairest skin and most sun exposure have the greatest risk.

Differential Diagnosis (Other conditions with similar appearance)
Bowen’s disease
Cutaneous horn
Actinic keratosis
Chondrodermatitis nodularis helicis
Basal cell carcinoma

Key Points
*Diagnosis based on appearance of the affected area
*Skin biopsy will be performed to confirm diagnosis and rule out other conditions
*Invasive SCCs may require imaging tests to determine the extent of involvement

SCC is typically diagnosed based on the appearance of the lesion. A biopsy of the lesion will confirm the diagnosis and rule out other conditions. In the case of invasive SCCs, imaging tests may be performed to determine the extent of lesion involvement.

*Treatment predicated on lesion location, size, and histopatholgy
*Goal of treatment is removal of the lesion and destruction of cancer cells
*Preventative measures include skin protection and skin examination
*SCCs may recur on the removal site

Treatment of SCC is predicated on lesion location, size, and histopathology.  SCC is typically treated by removal of the lesion, usually accomplished by surgical means.  Early SCC are often treated by electrodessication and curettage.  This procedure involves using a scalpel-like tool, called a curette, to scrape away cancer cells.  This is followed by electrodessication (electric spark to further destroy tissue) of the base to further increase the cure rate.  Dermatologists are very experienced with this technique and have cure rates of 90-95%.  

For SCC in situ, there are two topical creams that may be offeredto treat this early form.  Imiquimod (an immune system modulator) or 5-fluorouracil (a topical chemotherapy) can offer cure rates of about 90% for thin SCC.  

Your dermatologist will offer surgical excision as an option for deeper and more aggressive tumors.  The tumor is removed by scalpel excision with an appropriate margin of normal skin surrounding the tumor.  The resultant defect is then repaired with sutures or staples.    

For some SCC's, Mohs Micrographic surgery may be recommended.  Some indications for the Mohs technique include:  large tumors (greater than 2cm), deeply invasive SCC, SCC showing perineural invasion, SCC showing other signs of aggressive growth on histopatholgy, and recurrent lesions.  

SCCs at the highest risk for distant spread (metastasis), in cases which have already metastasized, and in inoperable cases, radiotherapy (radiation treatment) is used to combat the condition.