AJR:204, January 2015 211 sions recommended for biopsy are ultimately determined to be benign [7, 8]. Many of the benign enhancing lesions seen on breast MRI are not visualized by mammography or breast ultrasound and, therefore, require the more time-intensive and costly MRI-guided breast biopsy. Furthermore, when benign le- sions do not show distinct benign morpho- logic features and are associated with con- cerning kinetic features, the pathologic findings may be considered discordant and lead to a repeat of the MRI-guided biopsy. Recently, an increase in the MRI detection of benign apocrine lesions and, in particu- lar, cystic apocrine metaplasia (also known as papillary apocrine change or cystic papil- lary apocrine hyperplasia), has been report- ed [7, 9]. Cystic apocrine metaplasia is a sub- set of fibrocystic changes featuring discrete clustered cysts that are lined by apocrine ep- ithelium. The architecture of the apocrine epithelium may be of variable complexity: Breast MRI-Detected Cystic Apocrine Metaplasia: Imaging Features With Microvessel Analysis and Histologic Correlation Roberta M. diFlorio-Alexander 1 Jonathan D. Marotti 2 Jesse S. Bond 2 Mary C. Schwab 2 Vincent A. Memoli 2 Wendy A. Wells 2 Steven P. Poplack 1 diFlorio-Alexander RM, Marotti JD, Bond JS, et al. 1 Department of Radiology, Dartmouth-Hitchcock Medical Center, 1 Medical Center Dr, Lebanon, NH 03756. Address correspondence to R. M. diFlorio-Alexander (Roberta.M.diFlorio-Alexander@Hitchcock.org). 2 Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, NH. Women’s Imaging • Original Research AJR 2015; 204:211–218 0361–803X/15/2041–211 © American Roentgen Ray Society C ontrast-enhanced breast MRI is indicated for screening patients who are at high risk for the devel- opment of breast cancer, deter- mining the extent of disease in newly diag- nosed breast cancer, and evaluating a small subset of breast lesions that are indetermi- nate by other imaging modalities. It has been established that breast MRI is highly sensi- tive for the detection of breast cancer, with most recent studies reporting sensitivity be- tween 89% and 100% [1–5]. Yet, the speci- ficity of breast MRI remains suboptimal. The detection of breast cancer on MRI is largely dependent on the enhancement of the malig- nancy. This enhancement is due to a number of biologic factors, including an increase in vessel number and size, increased vascular permeability, and increased cellularity [6]. However, benign lesions may also show en- hancement on breast MRI. Prior studies have shown that most (60–80%) enhancing le- Keywords: breast, cystic apocrine metaplasia, MRI DOI:10.2214/AJR.14.12869 Received March 19, 2014; accepted after revision May 10, 2014. R. M. diFlorio-Alexander and J. D. Marotti contributed equally to this manuscript. Preliminary results from this study were included in a scientific abstract presented at the United States and Canadian Academy of Pathology annual meeting, March 4, 2013, and published elsewhere (Bond JS, diFlorio-Alexander RM, Memoli VA, Wells WA, Marotti JD. Microvessel density and distribution in MRI-detect- ed benign breast lesions [abstract 119]. Mod Pathol 2013; 26[suppl 2]:31A). Adapted with permission from Nature Publishing Group. OBJECTIVE. The purpose of this article is to characterize the histologic vascular fea- tures and distinguishing MRI features of cystic apocrine metaplasia to better understand im- aging-pathology concordance. MATERIALS AND METHODS. Retrospective review of 261 consecutive MRI-guided biopsy cases was performed. Pathology results were reviewed for all biopsies; cystic apocrine metaplasia was identified as the predominant finding in 19 cases (7%). CD31 immunohisto- chemistry was subsequently performed on the most representative block of cystic apocrine metaplasia, and microvasculature was evaluated using computer-assisted image analysis. The contrast-enhanced MRI examinations correlating with the cystic apocrine metaplasia cases were independently reviewed by two radiologists specializing in breast imaging; lesions were analyzed for morphologic, kinetic, and T2 characteristics. RESULTS. On MRI review, 17 of 19 (89%) lesions were 10 mm or smaller. Washout ki- netics were present in 11 of 19 (58%) lesions, and 14 of 19 (74%) lesions were at least partially hyperintense on T2-weighted sequences relative to adjacent glandular tissue. Cystic apocrine metaplasia had a higher percentage area (mean, 4.1%) of CD31-immunostained microvessels compared with background fibroglandular tissue (mean, 1.2%). CONCLUSION. Cystic apocrine metaplasia should be considered in the differential di- agnosis of a T2-hyperintense enhancing focus or subcentimeter smoothly marginated mass, even if associated with washout kinetics. Cystic apocrine metaplasia contains a statistically significant increase in microvessel area compared with background fibroglandular tissue and fat and, therefore, may be considered a concordant result for this set of imaging findings. diFlorio-Alexander et al. Features of Cystic Apocrine Metaplasia on MRI Women’s Imaging Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved