I mentioned this to a friend, who opened his hand to show me his Dupuytren's Contracture.
It is quite clearly a Dupuytren's Contracture.
Dr Madman, however, took one look at it and cried, 'Pwobably not cancer! A Dupuytren's Contracture!'
So, to be honest, I'm assuming it's not cancer, and wondering why he felt the need to bring the subject up.