Because of the location of the bump, chances ar your dog would need general anesthesia in order to do a biopsy. And, if I'm interpreting you correctly by assuming the lump is around her anus, lumps in this area can be cancerous, but even if they aren't they may bother the dog enough to rub to lick the area to cause irritation and infection. Because of this, it's often better for the animal to remove the lump and send samples of it for histopathology rather than just do a biopsy.
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