Melanoma is one of the most common forms of cancer in the United States.

It can be life-threatening just 6 weeks after being diagnosed. This form can also be resistant to many traditional cancer treatment like chemo.

But a new kind of treatment could be a game-changer for melanoma patients.

To pool play, most of Christine Mcgonigal's fondest experiences with her grandkids happen outside, but all that came to a halt when she discovered a raised bump on her right leg.

"It was about the size of this thumbnail," McGonigal said.

Doctors said it was melanoma, an often-aggressive skin cancer linked to UV light. After more than a year of treatment, the tumor kept coming back.

Imlygic is the first FDA approved viral drug for melanoma with an unexpected ingredient.

"It's a modified form of herpes virus. It not only kills melanoma cells, but it also exposes the byproducts of its melanoma cells to the immune system," Mercy Medical Center Surgical Oncologist Vadim Gushchin said.

Helping prevent new cancer cells from forming in tumors visible by ultrasound.

"You draw the drug into the syringe and inject it directly into the melanoma," Gushchin said.

While some may experience temporary flu-like symptoms after injections, it's uncommon to actually contract the herpes virus from Imlygic.

"They are actually able to see how lesions disappear in front of them, which is very rewarding," Gushchin said.

For Mcgonigal, it was a last resort that worked.

Her scars remain, but the melanoma hasn't come back in two years. So she's back in the sun, this time with sunscreen and a hat, to show the grandkids how to have some real fun.

Imlygic injections take about 10 minutes and are conducted over several months.

In clinical trials, Dr. Gushchin says seven in 10 patients saw a reduction in their melanoma tumors within about four months and three in 10 had their melanoma disappear for many months to years.