A complete excisional biopsy (removing the mass altogether) would tell you for sure what exactly this lump IS in order to give you some peace of mind. If this is a dermal (skin) mass, it is quite important to get an exact diagnosis as to what exactly it is - it could be a range of different lumps that can be either benign of malignant.
Best of luck following this up with your Vet and please do let me know what the exact diagnosis of this lump was once all the diagnostics have been carried. Do not panic in the mean time and just get your boy checked out when you next can.
Thank you and please now click ACCEPT.
Dr M D Edwards