Basal Cell Skin Carcinoma
Andrew Saul's Vitamin C website has this to say
Topical Vitamin C Stops Basal Cell Carcinoma
"Many thanks for posting the information on this. I am only a week and a half into treatment and my Basal Cell is nearly gone."
(OMNS Nov 9 2007) The most common form of skin cancer, basal cell carcinoma, often responds to a remarkably simple, safe, at-home treatment: vitamin C. Physicians and patients report that vitamin C, applied directly to basal cell skin cancers, causes them to scab over and drop off.  Successful use involves a highly-concentrated vitamin C solution, directly applied to the blemish two or three times a day. Vitamin C is selectively toxic to cancer cells, but does not harm healthy skin cells. This is also the basis for high-dose intravenous vitamin therapy for cancer.  Even higher concentrations of vitamin C can be obtained by direct application. The use of topical vitamin C to kill basal cell carcinoma has been known at least since 1971. Frederick R. Klenner, MD, wrote: "We have removed several small basal cell epithelioma with a 30 percent ointment" of vitamin C. 
One person, who reported that a 2mm diameter spot on the nose would not heal for months, had it disappear within a week with twice-daily concentrated vitamin C applications. Another patient reported that after dermatologist-diagnosed multiple spots of basal cell carcinoma were coated with vitamin C, the spots fell off within two weeks. 
Basal cell carcinomas are slow growing and it is rare for them to metastasize. This provides an opportunity for a therapeutic trial of vitamin C, provided one has proper medical diagnosis and follow-up.
Preparation of a water-saturated vitamin C solution is simple. Slowly add a small amount of water to about half a teaspoon of vitamin C powder or crystals. Use just enough water to dissolve the vitamin C. Using less water will make a paste. Either way, application with the fingertip or a cotton swab, several times daily, is easy. The water will evaporate in a few minutes and leave a plainly visible coat of vitamin C crystals on the skin.
Consult your doctor before employing this or any other self-care treatment. A physician’s diagnosis is especially important, since other forms of skin cancer, such as melanoma, are faster growing and more dangerous. If the vitamin C treated area is not improved after a few weeks, a doctor should be consulted once again.
 William Wassell, MD: Skin cancer and vitamin C. Cancer Tutor, Skin cancer and vitamin c
 Riordan NH, Riordan HD, Meng X, Li Y, Jackson JA: Intravenous ascorbate as a tumor cytotoxic chemotherapeutic agent. Med Hypotheses 1995; 44: 207-2 13.
and also Vitamin C as a Chemotherapy for Cancer
 Fredrick R. Klenner, MD: Observations on the dose and administration of ascorbic acid when employed beyond the range of a vitamin in human pathology. Journal of Applied Nutrition Vol. 23, Nos 3 & 4, Winter 1971. http://yost.com/health/klenner/klenner-1971.pdf
and DoctorYourself.com - Klenner Vitamin C Paper
 Age spots, basal cell carcinoma and solar keratosis. Newsletter v5n9
One reader says:
“After reading Pauling and Cameron’s book
Cancer and Vitamin C, I decided to put what I learned to the test. For more than 2 decades, I've gone to the dermatologist 2 or 3 times a year to remove the spots on my face. Last May, I had about 20 spots on my face and was about to make an appointment with the dermatologist. Instead, I decided to start applying ascorbic acid topically. It works beautifully! I still apply ascorbic acid daily in solution, and keep the new spots under control. As an a extra benefit, the skin on my face has taken on a more youthful appearance and its clear to me that loose and wrinkled skin is not an inevitable result of aging, (I'm 73), but rather a symptom of anascorbemia of the skin.”
“For many years, I've mixed up vitamin C powder and vitamin E oil into a ‘heavy’ liquid. Put this on a wart, or a skin cancer with a small bandage over it, and replace every day. The wart will drop off soon, and cancerous area will cure in about a week. We keep inventing the wheel.