PRL and myeloid sarcoma: Both PRLs and the central vein sign appear to be specific for MS and have shown specificity for MS comparable and in some cases greater than OCBs: one study of scans from 112 patients with CIS and 35 in a non-MS group taken in routine clinical assessments found that the presence of ≥ 3 lesions with central vein signs or one PRL had high sensitivity (70%) and specificity (86%) for predicting conversion from CIS to MS [107].