Here is a picture of a patient that had a biopsy of a little mole on her 5th toe.  It was not painful but didn’t look normal on examination.  Patient ended up having what is called a dysplastic nevus and they recommended removing the tissue.  This is why biopsies are done to make sure they are not dangerous.  Most of the biopsies I perform come back normal but occasionally they have abnormalities.  As well this patient was referred over to Worcester Dermatology with Dr. Camille Roberts here in Worcester.  
Below you can see an example of the biopsy report from the patient.  If you have any dark spots you are concerned with come in to the office for an evaluation.