What is basal cell carcinoma? President Biden's skin cancer explained

When President Joe Biden had cancerous lesions removed from his skin, he became one of 2 million Americans to be diagnosed each year with basal cell carcinoma.

It’s the most common type of cancer in the world, the American Academy of Dermatology notes.

Biden’s lesion — located on his chest — was removed as part of his comprehensive health assessment, the White House said. The lesion was later biopsied and confirmed to be basal cell carcinoma.

In addition to the biopsy, the president underwent curettage and electrodissection, a procedure in which skin growths are scraped and then burned off. All the cancerous tissue was removed, and no additional treatment is needed.

"The site of the biopsy has healed nicely, and the President will continue dermatologic surveillance as part of his ongoing comprehensive healthcare," a White House memo from March 3 read.

What is basal cell carcinoma?

It’s a type of skin cancer that grows slowly and is not life-threatening for most people, but if it’s not treated, it can grow deep, injuring nerves and blood vessels, according to the American Academy of Dermatology.

Basal cell carcinoma lesions do not tend to spread, as some more serious skin cancers, such as melanoma or squamous cell carcinoma, are known to do, as physician to the president Dr. Kevin O’Connor noted in his memo.

"They do, however, have the potential to increase in size, resulting in a more significant issue as well as increased challenges for surgical removal," he wrote.

This skin cancer often develops on the head, neck and rams — places on the body that have had a lot of sun exposure — and can be mistaken for a pimple, scar, sore or a patch of dry, irritated skin.

“The eyelids in particular are at a bit of a higher risk because we typically don’t put any kind of skin protection on those, and when we wear sunglasses, sometimes the sun can sneak in behind the sunglasses,” NBC senior medical correspondent John Torres said on TODAY in January, after first lady Jill Biden had two basal cell carcinomas removed, one from above her eye.

The AAD has photos of what basal cell carcinoma looks like. It often shows up as a shiny, raised and round growth that's most commonly red or pink in color.

Basal cell carcinoma is most commonly diagnosed in people over 50, but it can also occur in younger adults who’ve had extensive sun exposure, the National Library of Medicine noted.

Patients often first notice it as a spot, lump or scaly patch on their skin that’s growing or feels different from the rest of their skin, the AAD says.

What is Mohs surgery?

While the president underwent curettage and electrodissection, the first lady had Mohs surgery, another common skin cancer treatment. During the procedure, doctors remove skin on the affected area of the body layer by layer until no more cancer cells are found when the tissue is examined under a microscope, according to the National Cancer Institute.

“It’s a surgery that is made to minimize the amount of skin and tissue that is removed, but at the same time make sure that all the cancerous cells are removed,” Torres said.

Depending on how much skin is removed, the wound may need stitches or a skin graft, when skin is transferred from one part of the body to another.

Some patients whose basal cell carcinoma isn't too deep can be treated with a topical immunotherapy cream instead of surgery.

The temporary inflammation it causes can be startling, as one patient shared with TODAY:

Bottom line: Doctors recommend checking your skin regularly and reporting any changes to your dermatologist. Be especially on the lookout for the ABCDEs of melanoma — warning signs of the deadliest form of skin cancer.

This article was originally published on TODAY.com