By  BETH LEVINE

“How long has that been there?” my dermatologist asks at my annual skin exam. I wanted her to check out some moles on my shoulders but instead she is examining what I thought was a pimple on my nose. Now that I think about it, it has been there for a while, hasn’t it?

She takes a biopsy and a few days later the results floor me: actinic keratosis, aka a pre-cancerous lesion. I never would have looked twice at the thing. Fortunately, it was caught before it could turn into cancer and, even better, there are now new therapies to cure it. But the whole experience was a wakeup call.

As a fair-skinned, freckled, green-eyed redhead, I misspent my youth with baby oil and reflectors in futile attempts to achieve a fleeting tan. Usually I just ended up with a sunburn. Now I, along with millions of other sun worshipers, am paying an even bigger price: a heightened risk for developing skin cancer. It’s the country’s most common form of cancer with more than one million new cases diagnosed every year, according to the American Academy of Dermatology (AAD). And the rate of melanomas, the deadliest form of skin cancer, has doubled in the past 20 years.

Why the rapid increase?

Experts say the main reason is that we’re still not heeding the warnings about sun overexposure. Yes, some of the problem is due to a thinning ozone layer, which allows more radiation to hit the earth, but that’s just a small part of the story.

The truth is we’re still a culture that prizes a good tan as a sign of health and wealth. Compounding the problem is that when it comes to fashion, we’re wearing less and exposing more. Since skin damage is cumulative, the current rising rates are reflecting our youthful skin abuse. (That would be me. I have a memory of a vacation at age 13 when my father literally chased me around the pool with a bottle of suntan lotion.)

I can’t change the skin damage I have already done, but I can change my behavior from here on in. So can you. The first line of defense is early detection, which starts with knowing what to look for.

Malignant melanoma is the most dangerous form of skin cancer and can appear even on places not exposed to the sun. When checking for melanomas, remember the ABCD checklist for moles or suspicious changes: Asymmetry (halves don’t match); Border irregularity (edges are ragged or notched); Color (pigmentation is uneven); and Diameter (larger than the end of a pencil eraser).

Squamous cell carcinoma occurs most often on sun-exposed areas, usually the face. It appears as nodules or red, scaly patches.

Basal cell carcinoma usually appears as a small, fleshy bump. It may cyclically bleed and scab over.

Actinic keratosis is a precancerous growth. If left untreated, it can turn into squamous cell carcinoma. While it will not grow into melanoma, people who have it are at higher risk for developing melanoma. It looks like a rough spot or reddened patch, which may bleed and scab over.