Former NBA player Jason Collins announced on Friday that his glioblastoma, a type of cancer on the brain, has reached stage four. Collins, who is the first openly gay player in the NBA, told his story in an article at ESPN, told by one of their senior writer,s Ramona Shelbourne. There, Collins detailed his emotional and moving story of confronting the life-threatening disease, which he described as "dangerous," "very aggressive," and "extraordinary.""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," he wrote. "My glio is extraordinary for all the wrong reasons, and is "wild type"-- it has all these mutations that make it even more deadly and difficult to treat."Last September, Collins' family announced his cancer diagnosis, which he said was "intentionally vague" to allow himself to tell his story once he is able. Collins played 13 seasons in the NBA, where he is mostly remembered with a New Jersey Nets uniform, matching up against the LA Lakers' Shaquille O'Neal in the 2002 finals, and against the San Antonio Spurs' Tim Duncan in the 2003 finals. In his article, Collins revealed that he had warning signs last August when he missed a flight that would have brought him to the U.S. Open. "In August, we were supposed to go to the US Open, just as every year, but when the car came to take us to the airport, I was nowhere near ready. And for the first time in decades, we missed the flight because I couldn't stay focused to pack," he wrote. This comes mere months after he married his husband, Brunson Green, in Texas. The 47-year-old added that his mental clarity and focus went downhill from there, even recalling a moment where he could not balance himself after falling in his room. Jason Collins says he is taking new technology in Singapore to battle cancerJason Collins' cancer has been a rare kind, he wrote. Considering how tough his battle has been, Collins said he flew to Singapore to try a new technology to recover from the disease. "Due to my tumor's genetic makeup, the standard temozolomide (TMZ) chemotherapy for glioblastoma doesn't work on it. Currently I'm receiving treatment at a clinic in Singapore that offers targeted chemotherapy -- using EDVs -- a delivery mechanism that acts as a Trojan horse, seeking out proteins only found in glioblastomas to deliver its toxic payload past the blood-brain barrier and straight into my tumors," he explained. Collins last played in the NBA during the 2013-2014 NBA season with the Brooklyn Nets under head coach Jason Kidd, his former teammate. Collins, who came out as gay in 2013, averaged 3.6 points and 3.7 rebounds as he was known as a defense-first center throughout his NBA career.