When 20-year-old Olivia Nikolic noticed a rash forming on her hip, she assumed it was a bout of eczema. But when the rash spread — and did so quickly — to other areas of her leg, she would learn it was a sign of something far more serious: cancer, or stage 4 lymphoma, specifically.

“I was nothing but in disbelief that I had cancer,” Nikolic told news.com.au of her diagnosis, which she received on Valentine’s Day this year.

The young woman also experienced other symptoms that she would later learn were signs of lymphoma, such as near-constant fatigue and a dry cough she wrote off as “just a cold.” But weeks later, Nikolic sought medical attention when she “developed an intense shooting pain from her heart to her left shoulder,” news.com.au reports.

EX-CHEERLEADER'S SKIN CANCER LEFT HER WITH GRAPHIC, GAPING HOLE IN HEAD

“It was such an intense pain. It was so bad I’d cry. I couldn’t breathe,” she said, adding it was her fiancé who recommended she go to the hospital.

“I am so lucky he did, as I was told if I’d left it for two more weeks, I wouldn’t have made it,” she continued.

After performing X-rays, Nikolic’s doctors found a tumor and informed her she had stage 4 lymphoma. It's not clear where in her body the tumor was found.

“I am lucky enough to have a cancer that is curable. I am thankful for this life lesson because it’s going to shape me to be a better person.” — Olivia Nikolic

Lymphoma, per the Mayo Clinic, is a "cancer of the lymphatic system" or the body's "germ-fighting network."

"The lymphatic system includes the lymph nodes (lymph glands), spleen, thymus gland and bone marrow," it continued, noting lymphoma can "affect all those areas as well as other organs throughout the body." Lymphoma is typically categorized into two different subtypes: Hodgkin's lymphoma and non-Hodgkin's lymphoma.

Symptoms include unexplained weight loss, night sweats, fatigue and sometimes an itchy rash, among other signs, according to Healthline.

WOMAN’S BIRTH CONTROL IMPLANT IN ARM DISLODGES, MOVES TO LUNG: REPORT

“Even a few days before I went to the hospital, I had no clue that anything was wrong with me. I was with my family and my friends, having fun and enjoying life. It isn’t something you’d ever expect to go through," she said. "You always see it happen to other people, but you never think it would happen to you.”

Nikolic started the first of her six chemotherapy rounds shortly after receiving the diagnosis. She is still undergoing treatment, and news.com.au reports that her tumor has shrunk by half. Though she tries to stay in good spirits, the 20-year-old admitted she is “really struggling to come to terms with it.”

“It’s really impacted me a lot. I feel like I’m always tired and unable to do the things I want to. I’m only 20. I’m turning 21 this year. I should be planning my 21st in America, studying, and saving for a house — but I can’t do any of that,” she told news.com.au. “I just wish I was healthy enough to work and save and do the things I’d planned, but now I’m set back.”

She added she’s lost her hair, eyebrows, and eyelashes as a result of chemotherapy, and has also gained weight due to the steroids doctors have placed her on.

UK BOY WITH SEVERE, UNEXPLAINED BRUISING DIAGNOSED WITH RARE BLOOD DISORDER AFTER PARENTS ACCUSED OF ABUSE

“I used to feel really confident, and now I don’t feel like I’m good enough,” she said.

But, Nikolic noted, “I am lucky enough to have a cancer that is curable. I am thankful for this life lesson because it’s going to shape me to be a better person,” she said. “For as long as I live, I’ll never take anything for granted again."

Nikolic did not immediately respond to Fox News' request for additional comment.