These include (i) a cystic lesion (as observed in our series, case 13), (ii) when serum prolactin is low (for example when there is suppressed tumour activity due to continued DA use/too short withdrawal period/little active prolactinoma), (iii) technical issues (low tracer activity, co-registration mismatch), (iv) hyperplasia instead of adenoma. Here, PRL is linked to neoplasm.