Concerned About Skin Cancer? Here’s What You Should be Asking Your Dermatologist

Your skin is your body’s first line of defense. Taking care of it is essential, especially when it comes to skin cancer. In our bi-monthly blog series, “Psst! Here’s What You Should be Asking Your Dermatologist,” we dive deep into the important questions you should be asking your dermatologist. Find the answers you’ve been seeking and make informed decisions about your skin health.

This month, we chatted with Dr. Ann Haas, a Mohs Micrographic Surgeon from Sutter Medical Group in Sacramento, CA. One common concern is whether basal cell carcinoma can transform into squamous cell carcinoma or melanoma. Read on to gain some valuable insights from a renowned expert in the field.

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Doctor, I’ve had basal cell carcinoma. Will this transform to squamous cell carcinoma or melanoma? Can skin cancer transform from one type to another?

Actually, this is the question that I get the most.

If you have basal cell carcinoma, squamous cell carcinoma, or melanoma, you are definitely at risk of getting additional tumors of the same type or one of the other types of skin cancer. But once you have one type of skin cancer, that is what you have at that particular location. That particular skin cancer does not convert into another type of skin cancer and is not a precursor to a different type of skin cancer. For example, if you have basal cell carcinoma on the nose, that doesn’t mean it is an early squamous cell carcinoma, and if you have basal cell carcinoma, that doesn’t mean it is an early melanoma. It is basal cell carcinoma. One tumor is not a continuum. Basal, squamous, and melanoma are three separate tumor types.

So, the answer is no: If you’ve had basal cell carcinoma it’s not a precursor to squamous or melanoma; and no, one type of skin cancer does not transform to another type.

Having said all that, several different subtypes of basal cell carcinoma are important to dermatopathologists and dermatologists because some of those basal cell carcinomas have a slightly different degree of aggressiveness and that is important information that we can provide to our patients as it may impact both treatment and follow-up protocols.

I tell my patients that basal cell carcinoma is like ice cream. There are different flavors. Some of those flavors are slow growing and some are associated with an extra level of aggressiveness. For instance, the nodular basal cell grows like a nodule. I call that the ‘vanilla’ form because generally, what you see is what is usually most of the extent of the tumor. However, some higher-risk basal cell carcinomas (which include the sclerosing, morpheaform, micronodular or infiltrative forms of basal cell carcinoma), I describe as ‘tutti-frutti’ because there is often a lot is going on pathologically. Some of those higher-risk forms of basal cell carcinoma can extend roots, fingers or shoots within the skin that clinically look normal. It often requires more work to remove these types and they tend to recur more frequently, if they are not adequately treated with good surgical margin control.

These are the sorts of things that those of us who do Mohs surgery can encounter. After we put numbing medicine in, we debulk and do an excision with a narrow margin around the visible tumor. The patient waits in the office while we process their tissue, examine it under the microscope, and with these higher risk subtype of tumors, there is often more going on than we thought. There might be a tumor at the edge of what looked like entirely normal skin, and if that is the case, we go back and take another layer of skin.

Sometimes we encounter a hybrid subtype of basal cell called basosquamous carcinoma. Microscopically, it can have features of both squamous and basal cell carcinoma. These are not very common and we treat them the same way that we would any basal or squamous cell carcinoma.

Are individuals diagnosed with basal cell carcinoma at risk for squamous cell carcinoma and vice versa?

As I noted earlier, yes, people who have been diagnosed with basal cell carcinoma are at risk for squamous cell carcinoma because it’s the same set of circumstances, for the most part, that have caused either one of those problems. Squamous and basal cell carcinoma are caused primarily by ultraviolet radiation exposure. There is a slight difference. Squamous cell carcinoma may be caused by people who have had cumulative long-term exposure. Basal cell carcinoma may be seen in individuals with intermittent, intense sunburns or childhood exposure. But frankly, I think that most of us have a combination of those. We are all out there getting exposed. Over exposure to ultraviolet radiation damages our DNA over time. Once your DNA is damaged, your body is not able to repair the DNA damage, then you can develop skin cancer.

I want to reiterate that the most common cause of skin cancer is ultraviolet radiation exposure. That is the single most important variable that we have control over. After all, you don’t have to play tennis at high noon. You can play golf with a broad-brimmed hat that covers your ears and neck. Also, sunscreens have gotten so much better in the last several years. Of course, we must mention tanning beds just to illustrate how dangerous they are. Those are swearing words—indoor tanning! Do not use tanning beds because indoor tanning equipment emits ultraviolet radiation and can cause of basal cell carcinoma, squamous cell carcinoma, and melanoma.

Outside of ultraviolet radiation exposure, there are some more unusual causes of these types of skin cancers. Many years ago, we used to see squamous cell carcinoma in people who had arsenic wells or were exposed to arsenic, especially in the more rural communities, but these days that is pretty uncommon. Smokers are prone to squamous cell carcinoma. They can develop squamous cell carcinoma at an earlier age. Some specific occupations can put individuals at higher risk for skin cancer—pilots, lifeguards, and firefighters, are some examples. Certainly, I see many people with immune system deficiencies who have developed skin cancer. People diagnosed with leukemia and organ transplant recipients mostly have squamous cell carcinoma, but we do see basal cell carcinoma in that group as well. When we see squamous cell carcinoma developing in the genital area, the perirectal area, or the fingernails, we think about the Herpes virus because there are many types of Herpes viruses in our environment, and a handful of them will cause squamous cell carcinoma, particularly in these locations.

Also, occasionally, we see both squamous cell carcinoma and basal cell carcinoma in areas of chronic wounds—protracted wounds that don’t heal on the leg, for example—those individuals may have had trauma. I recently had a patient who was severely burned as a child, and as an adult had developed a basal cell carcinoma at the edge of the burn scar.

Again, these examples are more unusual causes of skin cancer. It is ultraviolet radiation that you need to protect your skin and eyes from.

Are there any visual differences on their skin that individuals should look for?

Sometimes. We recommend a high degree of suspicion in people who are at risk or who have had previous skin cancers. Anything on your skin that is new and symptomatic, for instance if it itches, bleeds, crusts and wasn’t there last year, should be looked at by your doctor—this is particularly important for people who have a history of squamous cell carcinoma and melanoma because those are the two subtypes of tumors that can potentially metastasize. We especially want to know if there are changes in the skin of these patients. The lesion may be completely benign, but that sort of change within an individual with that history always warrants attention.

There are some characteristics of squamous cell carcinoma that I sometimes think our nurses can diagnose over the phone. For example, if one of our frequent-flier, sun-damaged patients calls our office and says, “I have this crater-looking thing that is starting to grow on my leg. It’s growing really fast, and it’s painful.” This call obviously warrants an appointment and, likely—a biopsy for definitive diagnosis.

Some types of squamous cell carcinomas in specific locations have a classic presentation but some basal cell carcinomas of the superficial form look just like the superficial form of squamous cell carcinoma. Both basal cell and squamous cell can ulcerate, as can melanoma on occasion. Sometimes, the pre-squamous cell carcinomas, those lesions that we call actinic keratoses, can also look like early basal cell carcinoma or superficial squamous cell carcinoma. There is also a subtype of melanoma without pigmentation. They are called amelanotic melanomas and they usually look like basal cell carcinoma. We biopsy them thinking they are most likely a basal cell carcinoma. And we are surprised when the pathology report comes back as an amelanotic melanoma.

Experienced dermatologists will almost always perform a biopsy.

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Asking the right questions can help you understand your diagnosis and make informed decisions about your treatment options. We hope you found this Q&A helpful. These suggested questions are a starting point to help you learn more about skin cancer. You are also encouraged to ask your dermatologist additional questions that are important to you.

Thank you, Dr. Haas, for providing valuable insight and guidance many newly diagnosed patients need during this challenging time.