I had no idea that men could get breast cancer. Then, I was diagnosed with stage 4 cancer.

• Zac Yarbrough is an outdoorsman who competes in professional fishing tournaments.
• He was diagnosed with breast cancer four years ago.

This as-told-to essay is based on a conversation with Zac Yarbrough. It has been edited for length and clarity.

Five years ago, I was swimming in a pool with my toddler daughters. My arm brushed against my chest, and I noticed a knot beneath my left nipple. It was odd, but I tried not to give it a second thought.

Over the next few months, I traveled the world, competing in professional fishing tournaments. As I did, the lump on my chest grew and grew, until it was almost the size of a golf ball. I looked like I had a boob.

At that point, I knew I couldn't ignore it any longer. I went to my doctor and saw a look of concern flash across his face. He sent me across the street for a mammogram — something I'd never considered having as a 38-year-old man. The next day, results from a biopsy confirmed that I had breast cancer.

The cancer had spread to my lungs

The cancer had spread to my lymph nodes. Doctors also saw a few spots on my lung; later tests confirmed those were cancer, too. I was diagnosed with stage 4, or metastatic, breast cancer. There's no known cure.

The toughest part of my cancer journey has been knowing that I avoided seeing doctors for months. In the US, about 1% of breast-cancer diagnoses are in men, according to the Centers for Disease Control and Prevention. But many people, like me in the past, have no idea that guys can get breast cancer. Because of that, most men with breast cancer are diagnosed later than women, a study on the website for the National Library of Medicine found.

The delay in diagnosis can mean the difference between life and death. With early detection, nearly 99% of breast-cancer patients are alive five years after their diagnosis, the American Cancer Society says. By the time cancer has spread, only 30% of patients make it five years.

I had surgery within days

Within five days of my trip to the doctor, I had a radical mastectomy, where the nipple, areola, muscle, and lymph nodes around the breast are removed. The surgery was a no-brainer for me. It changed my body, but I knew that would give me my best chance at survival. For that, I don't mind having scars.

I was in the hospital for only a day or two. The next week, I competed in a marlin fishing tournament. That reminded me of everything I loved about the outdoors and gave me a big morale boost.

Then it was time to get to work with chemotherapy and radiation. As a lifelong athlete and former college football player, I had a lot of mental strength to draw on. My dad told me to approach treatment like another football injury. That mindset has helped me get through 12 rounds of chemo, more than 36 radiation treatments, and a host of clinical trials and experimental treatments.

I'm still living my life, and still fishing

These days, I'm on a medication regimen and get chemotherapy once every three weeks. I just got a scan that showed the best results I'd had in years. My body is responding well to treatment. I'm optimistic since there are new cancer treatments being developed every day.

Mentally, I'm determined to keep living life as I always have. There's just too much life to live. I learned early on that I could be tired at home on the couch, or I could be tired in the great outdoors. I'll choose the water or the woods any day. The first 15 minutes of light and the last 15 minutes of light each day are my sacred time.

Recently, I participated in the same marlin fishing tournament that I did just after my mastectomy. My team spent seven hours reeling in a prize fish that would have been worth millions of dollars. But at the last minute, the line snapped. I was disappointed, but I understood: That fish was a fighter too. She wanted to live just as bad as I do.