title: Does size matter? Positive predictive value of MRI-detected breast lesions as a function of lesion size.
abstract: OBJECTIVE
  The purpose of this study was to determine the impact of lesion size on the positive predictive value (PPV) of biopsy in MRI-detected breast lesions.
  
  
  METHODS
  A retrospective review was performed of 666 consecutive nonpalpable, mammographically occult lesions that had MRI-guided localization. MRI examinations were performed using a 1.5-T magnet. Lesions were measured by the interpreting radiologist before biopsy. Malignancy rate versus lesion size was determined.
  
  
  RESULTS
  The median MRI lesion size was 1 cm (range, 0.3-7.0 cm). Malignancy was present in 149/666 (22%) lesions, of which 80 (54%) were ductal carcinoma in situ (DCIS), 66 (44%) were invasive cancer, and three (2%) were lymphoma. The frequency of malignancy increased significantly (p = 0.0005) with lesion size, with malignancy found in one (3%) of 37 lesions less than 5 mm, 44 (17%) of 254 lesions 5-9 mm, 37 (25%) of 151 lesions 10-14 mm, 21 (28%) of 74 lesions 15-19 mm, and 46 (31%) of 150 lesions 20 mm or larger. Lesions less than 5 mm accounted for 37 (6%) of 666 lesions that had a biopsy and one (< 1%) of 149 cancers (one DCIS). Among lesions less than 10 mm, the likelihood of malignancy was highest in postmenopausal women (22% malignant) and in the extent of disease setting (22% malignant), and lowest in premenopausal women (10% malignant) and in the high-risk screening setting (10% malignant).
  
  
  CONCLUSIONS
  The PPV of biopsy for lesions identified at breast MRI using a 1.5-T magnet significantly increased with increasing lesion size. Biopsy is rarely necessary for lesions smaller than 5 mm because of their low (3%) likelihood of cancer. Further work is needed to develop an algorithm that uses size in addition to other patient and lesion factors to guide biopsy recommendations for MRI-detected breast lesions.
authors.affiliation: Department of Radiology, Breast Imaging Section, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021, USA. libermal@mskcc.org
authors.forename: Laura
authors.initials: L
authors.lastname: Liberman
authors.forename: Gary
authors.initials: G
authors.lastname: Mason
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Morris
authors.forename: D David
authors.initials: DD
authors.lastname: Dershaw
mesh_terms: D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D001943:Breast Neoplasms / Q000473:pathology*; D002278:Carcinoma in Situ / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D011237:Predictive Value of Tests; D012189:Retrospective Studies