A basal cell carcinoma (BCC) is one of the most common skin cancers in humans. Every year, there are over 4 million BCC diagnosed in the United States. While BCC is very common, it rarely spreads to internal organs or lymph nodes. However, it can be locally destructive and invade into the tissue around it. (www.skincancer.org/skin-cancer-information/skin-cancer-facts)
What causes BCC?
Sun exposure is the main risk factor for developing a BCC. In particular, childhood burns and prolonged sun damage predispose to BCC. Genetics also play a role in BCC formation, with fair skinned patients at much higher risk for developing it. Also, there are very rare genetic syndromes, such as Gorlin's syndrome, in which patients can develop many BCCs, often from a young age.
Ultraviolet (UV) light causes BCC by damaging the genetic material found in certain cells near the lowest (basal) layer of the epidermis. The exact cells which are damaged in BCC is currently debated, but it is known that UV light will damage certain parts (genes) of the genetic material that put the "brakes" on cell growth. With the "brakes" damaged, those cells keep growing and invade into local tissue.
Are there different types of BCC?
Yes! There are many subtypes of BCC which fall into three broad categories. All are based on how the BCC appears when removed and viewed under a microscope. Often, there is more than one sub-type in a tumor.
- Superficial BCC is a subtype in which the BCC is clinging to the epidermis (top layer of skin). The name says it all: the tumor is close to the skin surface and not invading into the dermis (lower layer of skin).
- Nodular BCC is the most common type of BCC. This form has large clumps of BCC in the dermis.
- Micronodular BCC is the most aggressive form of BCC and has many other names (morpheaform, infiltrative, etc). This subtype has tiny clumps of BCC under the microscope and often extends much further from the tumor than is apparent on inspection.
How can my BCC be treated?
The most common options include topical treatments (creams), surgical excision, surgical destruction, radiation therapy and oral chemotherapy. The type, location on the body, size and degree of invasion of the BCC will usually guide the treatment options.
Topical treatments include 5-fluorouracil (5-FU), imiquimod and photodynamic therapy. These topical treatments are most effective for the superficial form of BCC. These treatments usually involve some degree of redness and crusting for several weeks.
Surgical destruction (in contrast to surgical exicion) includes using a high frequency electrical current (electrodesiccation) or liquid nitrogen to destroy the BCC. Surgical destruction can be an effective treatment for some superficial and nodular BCCs.
For both topical and surgical destruction, there is no confirmation that the tumor was completely removed (i.e. clear margins).
Surgical excision refers to removing the tumor with a margin around it of normal-appearing tissue. There are two approaches to surgical excision.
- Traditional excision involves removing the tissue with a visible margin of normal skin around it, closing the resulting wound and sending the removed skin to a laboratory to check that the margins (outer surfaces of the tissue) are free of tumor.
- A micrographic excision (i.e. Mohs surgery) involves taking the tumor and smaller margin and checking the margins of the specimen while the patient waits. If there is tumor on the margin, another piece of tissue is removed and so on. The wound is repaired once the margins are cleared. Mohs surgery is widely known to be the treatment with the highest cure rate for all types of BCC.
After either form of surgical excision, the resulting wound need to be repaired. Shallow and small wounds can often be left to heal on their own (second intent healing). Mid-sized wounds can be closed by bringing the sides together in a line (linear closure).
The skin of wounds in tight areas (i.e. scalp or shin) or large wounds cannot be easily (if at all) brought together. To repair these wounds, a graft (skin harvested from another site on the body) or flap (skin flipped over adjacent to the wound) is performed. A graft creates an additional wound and a flap creates a larger wound. A recent advance, the SUTUREGARD ISR Device, allows a simple and effective means to relax skin and perform a linear closure, often avoiding of the need for a skin flap or graft.
Radiation therapy and medications (e.g. vismodegib) are usually reserved for tumors in which surgery is not possible due to size, location or invasion into local tissues. Radiation therapy uses very intense energy to destroy the tumor. However, this intense energy can also destroy normal tissue and blood vessels, complicating future surgical procedures in the area. Vismodegib, which is a pill taken by mouth, can be very valuable to shrink or potentially cure large and/or aggressive tumors. Sometimes, a combination of treatments (e.g. vismodegib followed by surgical excision) can be the best course for large and aggressive tumors.
When faced with a skin cancer diagnosis, it is best to seek out a provider who is experienced in skin cancer management. One good choice would be a member of the American College of Mohs Surgery.