ST. PETERSBURG, Fla. -- Tampa Bay Rays minor league pitcher David Hess says he is starting chemotherapy to treat a cancerous tumor in his chest.

Hess tweeted Wednesday that he went to an emergency room about a week ago after experiencing chest tightness and shortness of breath.

"After some scans, blood work, and time at the hospital we learned that I had a cancerous germ cell tumor sitting in the center [of] my chest pressing majorly against my heart and lungs," he wrote. "Today we got the final diagnosis and treatment plan that has chemo starting up on Monday to shrink and hopefully eradicate the tumor entirely."

The 28-year-old has pitched in the majors for Baltimore, Miami and Tampa Bay, going 6-22 in parts of four seasons. He finished this year with Triple-A Durham, where he was 6-2 with a 3.57 ERA.

Hess said those around him have showed "love, prayers, and support in ways that have been so amazing I don't think we can even put into words how grateful my family and I are.

"As we get ready to go into this treatment time, we are confident this will all be gone from my body and I'll be back doing what I love on a baseball field soon and be healthy while doing it," he added. "This is just the beginning of a great story."