The BIRADS scoring system used by Radiologists has a scale from 0 to 5 and is assigned to films to indicate what further investigation is needed. A BIRADS 4 indicates the need for a biopsy to define the nature of the abnormality seen on the exam. 25 to 50% of BIRADS 4 can be something other than malignancy. Regards .....
I think it means this....
Birads 4 means 'not characteristic of' cancer, but there is a reasonable chance. Birads 5 means 'characteristic of cancer'
But not positive.