More than 96,000 Americans are diagnosed each year with melanoma, the deadliest form of skin cancer. That’s quite a scary statistic, but it’s important to remember that when melanoma is diagnosed—and how quickly it’s treated—has a lot to do with a patient’s chances of survival and recovery.
When doctors discover melanoma, they look at the affected tissue under a microscope to determine how much cancer is in the body and whether it has spread to other tissues or organs besides the skin—a process called staging. Here’s what patients and loved ones should know about the different stages of melanoma, and what they mean for treatment and prognosis.
Stage 0: melanoma in situ
The earliest stage of melanoma is stage 0, also known as melanoma in situ or carcinoma in situ. “In situ” is a Latin phrase that means “in position,” and this diagnosis means that the cancer cells are present only in the epidermis—the body’s most superficial layer of skin—and nowhere else.
“This diagnosis has a very good prognosis,” Noelani González, MD, an instructor of dermatology at the Mount Sinai Icahn School of Medicine in New York City, tells Health. People with localized melanomas (stages 0, 1, and 2) who are treated quickly have a 5-year survival rate of 97%—meaning they are, on average, about 97% as likely to still be alive in five years as people who don’t have these cancers.
Treatment for this stage cancer involves a wide excision surgery, where the affected skin (usually a mole, but not always) is cut away and the wound is stitched and bandaged. “The skin will be removed with margins,” explains Dr. González. “That means that some normal skin will also be removed around the edges to make sure there aren’t any cancer cells left over.”
The removed skin is then looked at under a microscope to ensure that all of the cancer was removed with “clean” margins, says Dr. González. Because stage 0 cancer has not spread to any other tissues or organs, no further treatment is required.
According to the American Cancer Society, some doctors may recommend treating stage 0 melanoma with radiation therapy, a specialized surgery called Mohs surgery, or with imiquimod cream, a drug also used to treat other types of abnormal skin growths. Not all cancer experts agree on the use of these treatments, however, and wide excision is by far the most common type of treatment.
Stage 1 melanoma
When cancer spreads beyond the epidermis, it is no longer considered stage 0. The next earliest stage is stage 1a, which means that the tumor is less than 0.8 millimeters in thickness and shows no signs of ulceration, or breakdown of the epidermis layer of cells, under a microscope.
If the tumor is less than 0.8 millimeters and shows signs of ulceration—or if it is between 0.8 and 2 millimeters with no ulceration—it’s diagnosed as stage 1b. “In either case, the tumor hasn’t spread to any lymph nodes or any other organs,” says Dr. González, “and treatment is generally the same as with Stage 0.”
Stage 2 melanoma
Stage 2 melanomas are larger and show more ulceration than those in stage 1, but they also have not spread to any lymph nodes or other organs. They are divided into substages, depending on their size and ulceration.
If a tumor is between 1 and 2 millimeters in thickness and is ulcerated, or between 2 and 4 millimeters and not ulcerated, it’s diagnosed as stage 2a. If it’s between 2 and 4 millimeters and ulcerated, or more than 4 millimeters and not ulcerated, it’s stage 2b. And if it’s more than 4 millimeters and also ulcerated, it’s stage 2c.
Like stages 0 and 1, stage 2 means that the melanoma is still localized, and patients still have a 5-year survival rate of 97%. Wide excisions surgery is also the most common treatment for stage 2 melanoma.
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Stage 3 melanoma
When a melanoma is diagnosed as stage 3, it means that the skin cancer has spread to nearby lymph nodes or tissue. “We can see that it’s grown outside of the initial tumor, but there’s still no evidence that it’s spread to distant organs,” says Dr. González.
Stage 3 melanoma is broken into substages a, b, c, and d, depending on the tumor’s size, whether it is ulcerated, and how many lymph nodes or tissues it has spread to. Cancers like these, which have spread regionally but not yet to distant sites, have a 5-year survival rate of 64%.
To treat stage 3 melanomas, doctors often have to remove more than just the original tumor. “The physician will palpate your lymph nodes and if any are felt to be enlarged, they will likely be removed and sent for testing,” says Dr. González. “This involves a much larger excision, and usually leaves a significant scar.”
Doctors then examine the removed lymph nodes under a microscope; depending on their findings, they may recommend additional treatment—like more surgery, or radiation, immunotherapy, or experimental clinical trials—to reduce the chances of the cancer coming back.
Stage 4 melanoma
Stage 4 melanoma means that a person’s cancer has spread to distant lymph nodes or organs such as the lungs, brain, or the liver. This is also known as metastatic melanoma.
It is difficult to cure stage 4 melanomas, which is why the 5-year survival rate for these advanced cancers is only about 23%. But doctors will often remove the original tumor and affected lymph nodes with surgery, or attempt to shrink them with radiation. Depending on where the cancer has spread, they may also treat other affected organs with surgery.
Often, melanoma spreads to organs that can’t be treated with surgery. Instead, doctors will use radiation, immunotherapy drugs, or chemotherapy to keep the cancer from growing and reduce symptoms.
Some metastatic melanoma cancers also respond to targeted therapy drugs, which target specific proteins that are only found in cancer cells. These drugs haven’t been shown to cure melanomas or metastatic cancer, but they may help patients live longer and experience fewer symptoms.
How to protect yourself from melanoma
Fortunately, most melanomas are diagnosed in early, localized stages, says Dr. González, and most patients treated for melanoma make a full recovery. “But we do have patients that have ignored that funny looking mole for way too long, and it’s not uncommon to see cases that have metastasized to other organs,” she adds.
Melanoma tends to a very aggressive form of cancer, and it can progress quickly from one stage to another. Says Dr. González: “As soon as you see something unusual you should get it checked out, and as soon as you get a diagnosis, you need to be on top of the appropriate treatment.”
Risk factors for melanoma include ultraviolet (UV) light exposure (especially via indoor tanning), having fair skin and light hair, and having a close relative who’s also had melanoma. But monitoring skin for abnormal growths and changes is important for everyone, whether or not they are predisposed to skin cancer.
“Going to see your board-certified dermatologist yearly and doing regular skin exams may not seem that important,” Dr. González says, "but these are the things that could save your life."