At least it’s not cancer. Now I can rest easy, right?
DERMATOLOGY Precancer should not be ignored, though it is better than various stages of malignant cancer. Precancers more often are manifest on sun exposed skin and are detected and treated by a dermatologist. They can also be found within the mucosal epithelium tract.
What is precancer? An “actinic keratosis” is the most common precancerous growth encountered on sun exposed areas of the body. About 5% of actinic keratoses develop into squamous cell carcinoma. The lesions often appear as red, scaly areas of skin that do not heal.  A tiny polyp removed during a routine colonoscopy is considered a precancerous lesion. An oral melanotic macule is another precancer. On ocassion, precancers are discovered on non-UVB sun exposed areas of the skin, like the chest of someone routinely wearing a shirt when outdoors. Bowen's disease falls into this category.  Physicians examine specimens not just for cancerous tissue but precancers as well since histopathology differs between the two.
Though there is a low chance of precancers becoming malignant, ignored lesions increase the chance of developing into cancer. Treatment may involve imiquimod cream, biological therapy, freezing with liquid nitrogen (cryosurgery), radiation, or complete excision (curettage). Mohs surgery (discussed on the Understanding Skin Cancer poster) is a procedure for larger, recurring or difficult-to-treat skin cancers; the doctor removes skin growth layer by layer, examining each under a microscope, until no abnormal cells remain.  After treatment, continued followup visits are advised, as recurrence is common.
Preventing Skin Cancer
To prevent actinic keratosis and other precancerous changes associated with sun exposure, be sure to follow basic sun protection suggestions. 
- Avoid sun exposure between 10 a.m. and 2 p.m.
- Wear protective clothing such as long sleeves and a hat.
- Apply and frequently re-apply sunscreen of at least 30 SPF.
- Avoid tanning parlors.
Perform monthly self-examinations, looking for new or changing lesions, which have become scaly, rough, crusty or bleed. If you find a suspicious lesion, contact your dermatologist immediately. Make it explicitly clear why you're concerned, and include any personal or family history of cancer. Because a shortage dermatologists is plaguing the nation, you may also need to recruit your primary-care physician to help you land an appointment. 
The use of optical spectroscopy to diagnose invisible precancer in patients undergoing endoscopy and similar medical procedures is gaining popularity.  Some dentists use similar techniques during annual oral exams with florescence devices such as the VisiLite or VELscope. A thorough dermatologist should perform a full-body examination, not relying on patient self-exam. Have any persistent skin irregularities professionally evaluated, especially in cases of prior basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) anywhere on the body.
- How To Know if Your Pre-Cancer is Now a Cancer. healthcentral.com
- What Is Bowen's Disease what-is-skin-cancer.blogspot.com
- Skin cancer mayoclinic.com
- Precancer of the Skin midwestderm.com
- Dermatologist shortage could leave you dying to be seen msnbc.msn.com
- Spectroscopic diagnosis and imaging of invisible pre-cancer. nih.gov, Badizadegan K, et al. Faraday Discuss. 2004;126:265-79; discussion 303-11