The 'Read All About It' rapper tweeted from hospital after he found a suspicious lump on his head.
He gave his fans regular updates during his hospital visit earlier today (September 7).
Doctors have cut out a lymph node to be tested for any cancerous cells. He will be informed of the test results next week.
He wrote: "Got the pre anaesthetic on my head so the injection doesn't hurt as much apparently... We'll see.
"Yawn. Can we get this thing out of my head already?"
He later added: "A 5mm x 5mm lymph node.
"Now all I can hope is it isn't cancerous. Won't know until Thursday :("
Green also reassured his fans that he will still attend his gig tonight at the Pilton Party near Glastonbury, Somerset.
The rapper recently declared Simon Cowell a "genius" over his music industry achievements.
Watch the video for Professor Green's new single 'Avalon' below: