Context.-The increasing use of contrast-enhanced magnetic resonance imaging (MRI) of the breast as a valuable adjunct to mammography and ultrasound in the detection of breast lesions, in association with needle core biopsy taken from the suspicious areas, has major workload implications for histopathology laboratories wherever breast MRI is practiced. Objective.-To establish the number of histologic levels necessary for the evaluation of breast MRI-guided needle core biopsy specimens taken from suspicious areas on breast MRI examination. Design.-Retrospective histologic review of a series of breast MRI-guided core needle biopsies, initially examined routinely at 4 levels, in the Pathology Department at Mount Sinai School of Medicine in New York, New York. Results.-Accurate diagnostic classification was possible after examination of the first level in 95.4% of cases. For a small group of patients (4.4%), 4 levels were considered to provide additional useful information, although this information did not alter the diagnosis. In only a single case (0.2%) was it likely that routine examination of 4 levels could have led to an incidental finding of a very small intraductal papilloma (0.15 cm) present only at the second histologic level. However, this incidental finding would have not changed the patient outcome. Conclusions.-Needle core biopsies for MRI-detected abnormalities should be routinely examined at only 1 level. Further levels may be needed in occasional cases to identify more conclusively an associated pathologic abnormality and may be of particular value when assessing atypical intraductal proliferative epithelial lesions. (Arch Pathol Lab Med. 2009; 133: 1961-1964)
