It sounds like a fungus. A good camera repair shop should be able to disassemble the lens and clean it. If it's as minor as it sounds, the repair should be 100% successful. I've had it done on a couple of lenses, and all have remained clean.
Kostas Kavoussanakis wrote: > As I got no interest so far, it seemed to me that I buried my question > under the thread. Let me try again. > > The Kiron 70-210/4 I bought off ebay arrived today. I had a look at > the front element(s) and I see a reflection like a small splash on the > back of the front element or on the second element or sth like that. > Is that Mr Mushroom? Is that a goner? > > Any references on fungal infections and particularly detection? > Otherwise, what could be this problem? > > Not very hopeful, > Kostas