......A Keratoacanthoma lesion, also called "KA" by dermatologists, contains keratin and may look much like a red or pink volcano with an eruptive central plug of compact or breaking scale. The KA is considered a form of squamous-cell carcinoma by most authorities. However, some doctors consider KA to be a separate disease and not a malignancy. Indeed, in many cases, KA's behave in a rather benign fashion, neither destructive locally, nor invading, nor spreading internally.

......Nevertheless,, in medicine prudent doctors and patients do not want to miss a potentially serious problem. Therefore, since many KA' s have been reported to invade deeply, grow rapidly and destroy body parts and important structures like the nose and eyes, certain KA's, behaving in certain ways, located in special areas, merit the special attention. Because a growth has the potential, even if uncommon, to cause significant harm by invading locally or spreading distantly, that growth (in this case, KA) should be classified as skin cancer in order to alert doctors and the general public to be vigilant.

.....Some physicans or surgeons claim that with thousands of cases of experience, they can predict, many times, which KA's will cause trouble and which ones will not with great accuracy (even 90% would leave room for 10% error). There is even a hereditary (genetic, in families) form of KA, as well as an eruptive (comes in groups) form which can "pop" up with many KA lesions, especially on the arms and legs.

..... Commonly, more than one KA can arise on the leg, either all at once or over time. This special version of KA is called multiple "keratoacanthoma of the leg" and can be particularly distressing to both patients and doctors. Although KA may best be thought of as a well-differentiated form of squamous-cell carcinoma (usually not too destructive and not too much of a tendency to spread internally), KA can "pop up" on the legs commonly following surgery even for a nearby KA. It may not be best to use the word "recur" (resisted treatment) for a KA of the legs. This is because even after proper MOHS surgery (confirming that all the seeds and roots have been removed of a given KA) a new KA can "pop-up" very close to the area where the original KA was removed. Some patients might wrongly think their doctor missed the tumor. This is not necessarily the case. It has been long known that KA will pop-up following virtually any type of surgical treatment in the skin right near where an original treatment was done. Again, MOHS surgery has shown and proven that there are no missed roots connecting the old tumor with the new tumor. Therefore, it is very difficult to blame a doctor when a KA of the leg arises nearby where another KA surgery was performed even if it was MOHS surgery that was properly performed to remove the KA.

.....It is possible however, to have a recurrent (same exact tumor comes back again) KA. For example, if a KA "pops-up" right below the scar of the original removal it is likely a recurrence (missed cancer, failed treatment). If the KA "pops-up" exactly in the edge of the scar of the previous removal method for the KA and more lesion lies on the inside rather than on the outside of the scar, it is also likely a recurrence.

.....However, the author believes that the growing of multiple or many KA all at one time or at different times on the front of the legs should be called a "field-effect." The Web site author has found a new treatment to help reduce this type of KA. This treatment has been extremely effective for the Web site author's patients. However, the Web site author cautions the public that not just any doctor should provide this treatment. The gel Tazarotene is topical (applied on the outside of the skin) and is painless when first rubbed "on." The medication may in some cases be dangerous and when improperly used may cause many types of problems ranging from birth defects to holes in the skin. The Web site author has several patients on a special pulsed schedule (not continuous) application of spot treatment that "melts away" both newly arising and old KA . In these cases, the KA vanished to examination with the naked eye without scarring or surgery.

.....Some dermatology texts state that the best treatment for KA is an excision that generates a specimen for a dermatopathologist to read under the microscope. The author believes that the need for a specimen is important when the KA is occurring in a critical area where there is little tissue, e.g., eyelid, ear or nose. The most accurate and tissue-sparing form of excision is Mohs Surgery. However, you should consult your insurance carrier or state Medicare department to see if it will cover Mohs Surgery on a KA located where yours is located. If the lesion is on the eyelid, lip, ear or nose, it is certainly hoped that Mohs Surgery will be covered.

......The difficulty with treatments such as liquid nitrogen, topical 5-FU (Efudex, fluoroplex), and scraping and burning (C&D) when used on KA is that the KA may be deep and require very deep treatment. Also, the KA may grow more rapidly or deeply than the treatment reaches. As long as the patient is willing to accept the failure rate, then these non-excisional treatments may be used.

......However, there is now a promising non-surgical treatment option for the treatment of at least some KA and some squamous-cell carcinomas, injectable (not topical or rubbed on the skin) 5-FU (fluorouracil chemotherapy). Studies have shown a success rate of over 95% in treating squamous-cell cancers by injecting 5-FU with little scarring, usually less noticeable than proper cutting and sewing would leave. Of course, there is the potential downside of being one of the five percent of the patients in whom the injectable form of 5-FU does not work, leaving the tumor to disfigure and grow bigger during or after the treatment. Additionally, in the studies supporting such use of 5-FU cure rates are not done at 10 years or maybe even 5 years. This of course would influence the quality of the results of the study.

......KA can be very destructive, although with the eruptive type this is not the norm. KA's have been reported to destroy the entire nose and center of the face. In fact, the medical literature supports aggressive and accurate surgery for KA located in the center of the face because KA's located there tend to cause widespread destruction. The author has had many patients who have KA arising on the legs sent to him by other dermatologists. The doctors have properly treated the KA's there, only to see the KA's "pop up" several inches away. The doctors did not miss the KA's. However, by some unknown process, perhaps seeding, or a weak tendency in that area of skin or the reaction to the trauma of surgery, new KA's may form near an area that appears to have been properly treated for KA. In other words, there are occasional/some cases of KA that can be extremely frustrating to treat, either penetrating deeply or popping out like additional leaks in a dike, just as you put your finger in to stop one leak. Although these cases are not the norm, doctors should be aware of these possibilities in order to help all patients.