Jason Collins announced in September that he was battling a brain tumor. This week, the 13-year NBA veteran player and league ambassador — famously the first pro athlete to come out as gay while still playing in the NBA or any major American sports league — went into detail discussing just how serious this is, in a story co-written for ESPN with Ramona Shelburne.

I have Stage 4 glioblastoma, one of the deadliest forms of brain cancer. It came on incredibly fast...

What makes glioblastoma so dangerous is that it grows within a very finite, contained space -- the skull -- and it's very aggressive and can expand. What makes it so difficult to treat in my case is that it's surrounded by the brain and is encroaching upon the frontal lobe -- which is what makes you, "you."

Collins describes how he and his husband, Brunson Green, were packing to head to the US Open tennis tournament in August when the symptoms came on quickly, most noticeable to others when he could not focus enough to finish packing for the trip. Not long after, his "mental clarity, short-term memory and comprehension disappeared," turning him into someone who was not really himself. Fortunately, with aggressive treatments of a new drug and radiation therapy, Collins has "come out of the fog" and is more himself again.

Collins also talks about fighting the disease, and he is currently in Singapore receiving specialized treatment (which he details in the must-read story).

We aren't going to sit back and let this cancer kill me without giving it a hell of a fight. We're going to try to hit it first, in ways it's never been hit: with radiation and chemotherapy and immunotherapy that's still being studied but offers the most promising frontier of cancer treatment for this type of cancer.

Collins, 46, and his twin brother Jarron Collins both went from dominating the Southern California high-school basketball scene to attending Stanford together. There, Collins helped lead the Cardinal to the Elite Eight one season and the Final Four the next.

Collins was selected by the Houston Rockets with the No. 18 pick in the 2001 NBA Draft, then was traded on draft night, along with Richard Jefferson, to the New Jersey Nets. Collins quickly became a key part of the Nets and was the starting center on the Jason Kidd-led 2003 team that reached the NBA Finals. Collins was a physical, rock-solid defensive center who played 13 NBA seasons for the Nets, Grizzlies, Timberwolves, Hawks, Celtics, and Wizards.

After retiring from playing, Collins became an ambassador for the league, serving in that role at a number of events.