my Ellie had a sebaceous cyst on her back/rump it would come up & i would clear it out when it got "ripe"
originally the vet thought it may be an abscess so put a needle in to draw of any fluid, nothing came out, he gently squeezed the area & some white cottage cheese type gunk came out (light pig-light gunk/ dark pig-dark gunk) No smell to it.
this was taken a month or so after the vet cleared it a little.
the hole area with the white bit in was where the needle was inserted, but this left a weak area to express the gunk without it spreading out under the skin.
the white dot/scabby area was dried up gunk, this would come out of the hole (never healed properly) as a hard scabby lump on top for the rest of the cottage cheese stuff to follow afterwards' was like squeezing a toothpaste tube
does this look like your guineas scabby bit? as Helen suggested it could be a sebaceous cyst like My Ellies.
she had hers about 2.5 to 3 years & it never bothered her much, sometimes she would have a nibble at it & make it bleed a little.
sometimes it needed clearing after a month, other times it would be nearly 3 months. have a vet show you how to clear it properly if it does turn out to be a seb cyst
hope these pics help?
