One of my relatives sows has a large lump on one of its nipples. The lump is pretty solid, cant get pic sorry.
This would be a mammary tumour. Get her to a vet to have it removed if not too big or pig too old, if not drugs to shrink it, probably best to neuter if mammary tumours are starting to form. What age is the pig?
Lumps need a trip to the vets to be examined. Vet will stick a needle in and "pull up" (aspirate) some of the fluid in the lump which should help to determine if ti is benign (harmless) or not.
Guinea pigs aren;t reknowned for tumours/cancer..many of thier lumps are either cysts or beign fatty lipomas....i.e. harmless. However the mammary gland IS a possible site for a nasty tumour so this can;t be ignored and needs to be checked sooner rather than later. If it is a tumour, it can be operated on/removed and there should be no further problem porividng it is got soon enough.
So best approach is to identify a cavy savvy vet if you haven;t already got one and get an appointment for an inspection to put your mind at rest.
Whereabouts are you?
HTH
x
Cumbria Rescues.
Sokel Guinea Pig Rescue
Alston
Tel: 07818885260 / Email / Website
Becklen Guinea Pig Rescue
Penrith
Tel: 07540 870045 / Email / Website
Animal Concern Cumbria
Carlisle
Tel: 01228 593649 / Email / Website
Source: http://www.guineapigrehome.org.uk/gp/centres.asp
Be worth phoning the rescues and asking who they use as there vet!