Why would a doctor mark an ultrasound results 'recall' when there are nodules and cysts present but no action is to be taken as likely benign?

Need followup: Recall suggests that there is no discrete lesion that can be identified that requires biopsy. Nodules suggestive of fibroadenoma and cysts which are duct spaces with fluid do not get biopsies. Follow up requires repeat ultrasound, or even MRI to examine for progression and then deciding if a specific area needs excision for histologic exam.