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EDUCATION EXHIBIT

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Rare Breast Lesions: Correlation of Imaging and Histologic Features with WHO Classification1
ONlINE-ONly CME
See www.rsna .org/education /rg_cme.htmlAbid Irshad, MBBS • Susan J. Ackerman, MD • Thomas L. Pope, MD Christopher K. Moses, MD • Tihana Rumboldt, MD • Beata Panzegrau, MD Mammographers occasionally are surprised by the diagnosis of a rare lesion at breast biopsy. The imaging features of some breast lesions are unfamiliar because they are rarely seen in routine mammographic practice and they are not well described or well documented inthe radiologic literature. Moreover, there may be wide variation in the appearances of rare breast lesions at mammography and ultrasonography (US). In addition, although a few rare breast lesions have a typical imaging appearance, most have mammographic and US features similar to those of breast carcinomas, and a needle biopsy is almost always necessary to obtain a diagnosis. However, even when arare breast lesion is diagnosed on the basis of a needle biopsy, knowledge of the imaging features of such lesions may help the radiologist decide whether the results of pathologic analysis concur with the imaging findings and whether surgical excision is necessary. It is therefore important that radiologists be familiar with the broad spectrum of imaging features of rare breast lesions as well aswith the correlation between their histopathologic features and their current classification according to the World Health Organization classification system.
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lEARNING OBJECTIVES
After reading this article and taking the test, the reader will be able to:
■ Describe

the imaging and histopathologic features of various rare tumors that involve the breast. common US and mammographic featuresof these breast lesions. the need for correlating imaging and histopathologic findings for appropriate management of these lesions.

■ Identify

■ Discuss

RSNA, 2008 • radiographics.rsnajnls.org

TEACHING POINTS See last page
Abbreviations: CC = craniocaudal, GCT = granular cell tumor, MALT = mucosa-associated lymphoid tissue, MLO = mediolateral oblique, PASH = pseudoangiomatous stromalhyperplasia, WHO = World Health Organization RadioGraphics 2008; 28:1399–1414 • Published online 10.1148/rg.285075743 • Content Codes:
1 From the Departments of Radiology (A.I., S.J.A., T.L.P., C.K.M., B.P.) and Pathology (T.R.), Medical University of South Carolina, 169 Ashley Ave, Charleston, SC 29425. Received October 9, 2007; revision requested December 7 and received January 26, 2008;accepted February 25. T.L.P. is a consultant and member of the advisory board of Franklin & Seidelmann; all remaining authors have no financial relationships to disclose. Address correspondence to A.I. (e-mail: irshada@musc.edu).

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RSNA, 2008

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September-October 2008

RG ■ Volume 28 • Number 5

Numerous benign and malignant pathologic entities may involve the breast. In the mostrecent version of the World Health Organization (WHO) system for classification of breast tumors (1), lesions are classified according to their cellular origin (Appendix). In some cases, patients present with symptoms and signs, whereas in other cases a lesion or lesions are found incidentally at imaging. Unless a lesion has a typical benign appearance on mammographic images, breast carcinoma shouldbe included in the differential diagnosis; a tissue biopsy and analysis are required to exclude the diagnosis of breast carcinoma. Fine-needle aspiration and core-needle biopsy remain the standard means for differentiating less aggressive lesions from those that are more aggressive. In addition to frequently diagnosed pathologic entities such as fibrocystic changes, fibroadenomatoid changes,...