Wednesday, July 18, 2007

Skin Cancer--Basal Cell Carcinoma

 Updated 3/2017-- photos and all links (except to my own posts) removed as many no longer active.

Basal Cell Carcinoma (BCC) is the most common skin cancer. It typically occurs in areas of chronic sun exposure. BCC is usually slow growing and rarely metastasizes, but it can cause significant local destruction and disfigurement if neglected or treated inadequately. BCC are most commonly seen in the head and neck. Therefore, disfigurement is not uncommon. Loss of vision or the eye may occur with orbital involvement. This skin cancer likes to spread along nerves (perineural spread) and this can result in loss of nerve function, as well as deep invasion of the tumor. BCC are prone to ulceration and this provides a nidus for infection. Death from BCC is extremely rare. Prognosis is excellent with proper therapy. Early treatment is necessary to avoid disfigurement.

Many believe that BCCs arise from pluripotential cells in the basal layer of the epidermis or follicular structures. These cells form continuously during life and can form hair, sebaceous glands, and apocrine glands. Tumors usually arise from the epidermis and occasionally arise from the outer root sheath of a hair follicle, specifically from hair follicle stem cells residing just below the sebaceous gland duct in an area called the bulge. Causes include UV radiation, other radiation (X-ray, grenz-ray exposure), arsenic exposure, immunosuppression, Xeroderma pigmentosum, Nevoid BCC syndrome (basal cell nevus syndrome, Gorlin syndrome), Bazex syndrome, and a history of nonmelanoma skin cancer. Person with 1 nonmelanoma skin cancer are at increased risk of developing others in the future. The rate of new nonmelanoma skin cancer is 35% at 3 years and 50% at 5 years after an initial diagnosis of skin cancer.

Histologically, BCC is divided into 2 categories: undifferentiated and differentiated. Undifferentiated BCC has little or no differentiation and is referred to as a solid BCC. The subtypes of Undifferentiated (BCC with little or no differentiation is referred to as solid BCC) include Pigmented BCC, Superficial BCC, Morpheaform or Sclerosing BCC, and Infiltrative BCC. Differentiated BCC often has slight differentiation toward cutaneous appendages, including hair (keratotic BCC), sebaceous glands (BCC with sebaceous differentiation), or tubular glands (adenoid BCC). Noduloulcerative (nodular) BCC usually is differentiated.

The 5 most typical characteristics of BCC can be seen in pictures here. They are:
An Open Sore that bleeds, oozes, or crusts and remains open for a few weeks. This persistent, non-healing sore is a very common sign of an early BCC..
A Reddish Patch or irritated area. It may itch or hurt. Often these occur on the chest, shoulders, arms, or legs.
A Shiny Bump or nodule that is pearly or translucent and is often pink, red, or white. This bump may also be tan, black, or brown, especially in dark-haired people, and can be confused with a mole (moles aren’t shiny).
A Pink Growth with a slightly elevated, rolled border and a crusted indentation in the center. As the growth slowly enlarges, tiny blood vessels may develop on the surface.
A Scar-Like Area which is white, yellow, or waxy, and often has poorly defined borders. The skin may appear shiny and taut. This warning sign can indicate the presence of small roots, which make the tumor larger than it appears on the surface.

Imiquimod 5% cream has been used to treat superficial BCC’s. Duration of treatment varies from 6-16 weeks. Cure rates of 70-100% should be expected after a 6 week course of 5 times-per-week application.
Topical 5-FU 5% cream is sometimes used to treat small, superficial BCC’s. In thin tumors, cure rates of approximately 80% have been obtained using a twice daily application for at least 6 weeks. Percutaneous absorption of 5-FU is its major limiting factor, as it penetrates only 1 mm into the skin.
Interferon alfa-2b has shown some success in treating small (less than 1 cm), nodular, and superficial BCC’s. It is administered intralesionally, 3 times-per-week for 3 weeks. In appropriate tumors, cure rates of up to 80% have been obtained. Interferon has not become a mainstay in treatment fo BCC’s because of its cost, the inconvenience of multiple visits, the discomfort of administration, and its adverse effects.

Curettage may be used. It is a blind technique in which the specimen cannot be examined for margin control. This limits the usefulness of curettage in high-risk areas, such as the face and ears. Furthermore, the aggressive subtypes, such as morpheaform, infiltrating, micronodular, and recurrent tumors, are usually not friable and therefore difficult to remove by using the curette.

Surgical excision may be used to excise the clinically apparent tumor and a margin of clinically normal-appearing skin. This can be done in an ambulatory setting and provides the pathologist with a specimen to examine the tissue margins. It is more time-consuming and costly than curettage, but the margin can be examined. Margin of up to 4 mm may be needed to achieve a 95% cure rate. This margin can be difficult to obtain near the canthus of the eye/eyelid.

Mohs surgery involves removal of the clinically apparent tumor and a thin rim of normal appearing skin. The margin specimen is sectioned and marked so that the entirety of the undersurface and outer edges of the tumor are examined microscopically to minimize sampling error. Use of the frozen-section technique allows for an examination of tissue while the patient is in the office. Tissue is mapped microscopically so if any foci of tumor persist, further excision can be directed to only those areas to spare the normal tissue. With the Mohs technique, almost 100% of the tissue margins are examined. Excision and repair can usually be done on the same day. Of most impartance, Mohs micrographic surgical excision has the best long-term cure rates of any treatment modality for BCC. Cure rates for primary BCC are 98-99% with Mohs excision and 94-96% for recurrent BCC. The chief disadvantages of Mohs surgery are its increased expense and time required.

Radiation therapy can be an effective primary treatment for a variety of BCC’s. For most, cure rates approach 90%. It is especially useful for patients who cannot easily tolerate surgery. Radiation is also an excellent option in patients who refuse surgery because of the size of the lesion or its proximity to vital structures.

Cryotherapy is an effective treatment for nonaggressive BCC’s, with cure rates near 90%, in the hands of an experienced cryosurgeon. Patients must be willing to endure the immediate post-treatment swelling, resultant necrosis of treated areas, and unpredictable scarring that can occur with this approach.
Suggested Reading:
Rubin AI, Chen EH, Ratner D, "Basal-cell carcinoma." N Engl J Med. 2005 Nov 24;353(21):2262-9. Rubin AI, Chen EH, Ratner D, "Basal-cell carcinoma." N Engl J Med. 2005 Nov 24;353(21):2262-9.

1 comment:

Bill said...

I found some interesting information about Squamous Cell Carcinoma here. Check it out!