Posterior Acoustic Shadowing in Benign Breast Lesions

Transcription

1 Image Presentation Posterior coustic Shadowing in enign reast Lesions Sonographic-Pathologic Correlation Susan P. Weinstein, MD, Emily F. Conant, MD, Carolyn Mies, MD, Geza cs MD, PhD, Steven Lee, MD, Chandra Sehgal, PhD Objective. To show a variety of benign breast lesions that exhibit posterior acoustic shadowing on sonography. Methods. The cases illustrate a variety of pathologic breast conditions that were collected at a referral breast center at a tertiary medical center. Results. variety of pathologic conditions are discussed, with pathologic-imaging correlation. Conclusions. lthough posterior acoustic shadowing is a sonographic feature that is most commonly associated with mammary malignancies, this sonographic finding may also be seen with benign breast lesions. Key words: breast; posterior acoustic shadowing; sonography. Received July 2, 2003, from the Departments of Radiology (S.P.W., E.F.C., S.L., C.S.) and Pathology (C.M., G..), University of Pennsylvania Medical Center, Philadelphia, Pennsylvania US. Revision requested ugust 4, Revised manuscript accepted for publication ugust 13, ddress correspondence and reprint requests to Susan P. Weinstein, MD, Department of Radiology, University of Pennsylvania Medical Center, 1 Silverstein uilding, 3400 Spruce St, Philadelphia, P US. weinstei@oasis.rad.upenn.edu. reast sonography has become an indispensable tool in the evaluation of breast lesions. lthough breast sonography may play many different roles in breast imaging, perhaps one of the more important roles it plays is in lesion characterization. There are sonographic criteria that help guide in differentiating benign lesions from questionable ones that need to undergo biopsy. Some of the typical sonographic features of breast carcinoma include irregular margins, a long axis perpendicular to the skin, a heterogeneous echo texture, and posterior acoustic shadowing. 1,2 lthough 1 or more of these sonographic features may be seen with breast carcinoma, it is important to note that there is an overlap of the sonographic features, and some of these sonographic findings may be seen with benign breast lesions. In this article, we present a spectrum of benign lesions that exhibit posterior acoustic shadowing. lthough some benign lesions cannot be distinguished from malignant lesions on the basis of sonography alone, many of the lesions may be accurately diagnosed on the basis of a combination of sonography, mammography, and history. If biopsy is necessary, with the increased use of percutaneous breast biopsies, understanding the over by the merican Institute of Ultrasound in Medicine J Ultrasound Med 23:73 83, /04/$3.50

2 Posterior coustic Shadowing in enign reast Lesions lap in the sonographic appearance of benign and malignant lesions is particularly important when assessing concordance of the imaging appearance with the pathologic results. Materials and Methods Cases showing a wide variety of pathologic breast conditions were collected from a busy breast imaging center. The cases were evaluated by mammography and sonography. ll the cases had various benign breast conditions that exhibit posterior acoustic shadowing on breast sonography. Shadowing Lesions Fibroadenomas Fibroadenomas are perhaps the most common solid breast masses that undergo biopsy. They may vary greatly in size from microscopic masses to lesions that are larger than 10 cm. Fibroadenomas arise from the terminal ductal lobular unit. The usual fibroadenoma is composed of a benign neoplastic proliferation of stroma balanced by the expansion and stretching of non-neoplastic ductules. It forms a sharply circumscribed mass with an expansile character that compresses adjacent mammary parenchyma. s a consequence of generalized mammary involution, fibroadenomas in postmenopausal women often show atrophy, hyalinizing sclerosis, and calcification. Typically on sonography, fibroadenomas are well circumscribed and have an ovoid or lobular shape. The internal architecture may vary from homogeneous to heterogeneous 3 on sonographic evaluation. Once the fibroadenoma begins to undergo hyalinization, posterior acoustic shadowing may be seen (Figure 1). Up to 30% of noncalcified fibroadenomas may exhibit posterior acoustic shadowing. 1 This sonographic shadowing may be confusing to the imager if not recognized as part of a spectrum of sonographic findings of hyalinized fibroadenomas. In some cases, the shadowing is seen from the margin of the lesion, giving a slightly different appearance than the more typical central shadowing of cancer. dditionally, the degree of shadowing does not appear to be as dense as in the case of some malignancies that exhibit this characteristic, and the posterior wall of the fibroadenoma is often visible as a thin echogenic margin, as shown in our example. Granular Cell Tumors Granular cell tumors are uncommon neoplasms that may arise at any anatomic site; 16% occur in mammary parenchyma or associated soft tissue. 4 Granular cell tumors, first called granular cell myoblastoma, are now known to express markers of neural (Schwann cell) differentiation. lthough nearly always benign in behavior, they can mimic breast malignancies both clinically and on imaging evaluation. On physical examination, they are palpably firm and, because of an Figure 1. iopsy-proved fibroadenoma in a 57-year-old woman., Sonogram showing a hypoechoic nodule with posterior acoustic shadowing. The echogenic sharp posterior margin of the mass (arrow) is shown through the region of shadowing. Typically, the posterior margin is not visible in malignancies that have posterior acoustic shadowing., Medium-power view showing a fibroadenoma with hyalinized stroma. The lesion is well circumscribed (original magnification 100). The epithelium shows mild hyperplasia without atypia. The stroma shows scant cellularity composed of abundant collagen material and bland spindled stromal cells. 74 J Ultrasound Med 23:73 83, 2004

3 Weinstein et al infiltrative character, may become fixed to surrounding tissue and may cause skin retraction or dimpling. 5 Local wide excision is the therapy of choice given the infiltrative and locally aggressive nature of these benign lesions. t pathologic review, sheets and clusters of bland tumor cells are seen. The tumor cells are characterized by bland uniform nuclei with evenly distributed chromatin and conspicuous nucleoli and abundant granular eosinophilic cytoplasm. 6 There should be a lack of mitotic activity in the lesion. 6 Mammographically, an irregular spiculated mass may be seen, 4 as shown in Figure 2, although circumscribed masses also have been described. 5 Sonographically, a hypoechoic mass with posterior acoustic shadowing is often seen. 5 The sonographic image shows an echogenic interface anterior to the hypoechoic lesion. Radial Scars Radial scars are common, seen in up to 28% of mastectomy and large excisional biopsy specimens. Most are microscopic, multiple, and scattered, but some merge into a confluent mass-forming aggregate. Solitary larger ( 1.0- cm) examples may form a palpable mass or one that appears as a discrete lesion on a mammogram. Radial scars are benign lesions of unknown etiology that can mimic a malignancy on imaging and pathologic evaluation. Mammographically, these lesions show spicules originating from a central nidus (Figure 3). Unlike a carcinoma, with spicules originating from a central mass, the radial scar does not have a central mass but rather has a central area of architectural distortion. 7 t times, there may be fat entrapped in the central nidus, resulting in an area of lucency, which may suggest the diagnosis of a radial scar. 7 t pathologic evaluation, the characteristic feature is a central fibroelastotic area, which is surrounded by distorted ducts in a stellate pattern. 8 The microscopic appearance may vary depending on the amount of sclerosis, epithelial proliferation, and ductal distortion and entrapment. 8 Unlike a typical invasive ductal carcinoma, a radial scar may vary in appearance greatly depending on the mammographic projection. t sonographic evaluation, a hypoechoic mass with dense posterior acoustic shadowing may be seen. There are no sonographic features that would distinguish this from a malignancy. 9 The combination of the mammographic and sonographic features may suggest the diagnosis. Even though imaging features may suggest the diagnosis of a radial scar, biopsy is recommended because a definitive diagnosis may not be made on the basis of the imaging findings alone. Figure 2. Granular cell tumor in a 25-year-old woman., Sonogram showing an irregular mass with posterior acoustic shadowing., Pathologic specimen showing a stellate-shaped, 0.8-cm mass that arose in a very fatty region of the breast (original magnification 200). The microscopic pattern is typical: cytologically bland-appearing cells with abundant granular cytoplasm and petite nuclei (arrows) embedded in a dense fibrous stroma. There is a lack of mitotic activity. These features are consistent with the diagnosis of a granular cell tumor. There was subtle spiny infiltration of fat at the periphery, but there was no necrosis or mitotic activity. J Ultrasound Med 23:73 83,

4 Posterior coustic Shadowing in enign reast Lesions Excisional biopsy, rather than core needle biopsy, is recommended because of the risk of associated lesions with this entity, such as atypical ductal hyperplasia, intraductal carcinoma in situ, lobular neoplasia, and tubular carcinoma. 10 Diabetic Mastopathy Diabetic mastopathy was first described in the context of thyroiditis and arthropathy in 1984 by Soler and Khardori. 11 It is an uncommon condition occurring in patients with long-standing diabetes mellitus, although similar pathologic findings occur in nondiabetic persons. It is most often diagnosed in premenopausal women. Patients usually have a poorly defined, firm-tohard, nontender breast mass that can mimic carcinoma. The size may vary considerably from millimeters to several centimeters. 12 Mammographically, a mass is often not seen because of the presence of dense breast tissue. Therefore, sonography is helpful in characterizing the breast mass. t sonographic evaluation, an irregular hypoechoic mass with posterior acoustic shadowing may be seen (Figure 4). Given the clinical history and the sonographic features, the diagnosis of diabetic mastopathy may be suggested, but tissue diagnosis is recommended for confirmation. t gross pathologic evaluation, a discrete mass is usually palpable without being visible. The mass is caused by the dense hyalinized collagenization of intralobular and interlobular stroma populated by sparse enlarged, epithelioid fibrob- Figure 3. Radial scar in a 38-year-old woman., spiculated mass is shown on a spot magnification view in the craniocaudal position., Sonogram showing a small hypoechoic mass with dense posterior acoustic shadowing. There is suggestion of spiculations arising from the hypoechoic mass. radial scar was suspected on the basis of the patient s mammographic and sonographic findings. Gross examination of the tissue showed it to be predominantly fibrous in character, with a firm 0.3-cm nodule at the radiologically identified site. C, This nodule corresponds to a fibroelastotic center (arrow) from which radiates a corona of connective tissue bands and stretched terminal duct-lobular units, typical of a radial scar (original magnification 25). Some of the small ducts are cystically dilated because of local obstruction by this fibrosing process. C 76 J Ultrasound Med 23:73 83, 2004

5 Weinstein et al lasts and myofibroblasts; a ductocentric and lobulocentric lymphocytic infiltrate is often, but not invariably, seen. 4,11 Fat Necrosis Fat necrosis is a benign condition related to prior trauma or surgery. The condition is usually asymptomatic, although patients may have palpable breast masses. The mammographic appearance may be varied depending partly on Figure 4. Diabetic mastopathy in a 37-year-old woman with a 17-year history of insulin-dependent diabetes mellitus. On physical examination, a mobile 3-cm mass was palpated within the left upper inner quadrant. The patient s mammogram showed dense breast tissue without a focal mammographic abnormality., Sonogram showing a poorly marginated mass with posterior acoustic shadowing. iopsy revealed diabetic mastopathy., Medium-power view showing dense, keloidlike fibrosis and a perilobular chronic inflammatory infiltrate composed of small lymphocytes (original magnification 100). Scattered epithelioid myofibroblasts are also present. The combination of these histologic features is consistent with diabetic mastopathy. the remoteness of the inciting event relative to the time of the imaging evaluation. n irregular spiculated mass with or without calcifications, calcifications alone, an oil cyst, or no findings may be seen at mammographic evaluation. On sonography a hypoechoic mass with posterior acoustic shadowing may be seen (Figure 5). In the case of oil cysts, late in the evolution of Figure 5. Fat necrosis in a 43-year-old woman who had a recent history of a left mastectomy and a right breast reduction. The patient had a palpable right breast mass. The mammographic examination revealed no questionable findings., Sonogram showing an area of posterior acoustic shadowing. Given the clinical appearance and the sonographic finding, the patient underwent an excisional biopsy, and the diagnosis of fat necrosis was made., Medium-power view of fat necrosis showing chronic inflammation composed of lymphocytes admixed with foamy macrophages and a giant cell reaction (original magnification 100). J Ultrasound Med 23:73 83,

6 Posterior coustic Shadowing in enign reast Lesions fat necrosis, a circumscribed hypoechoic mass with or without posterior acoustic shadowing may be seen. The thin echogenic rim is usually visible regardless of the presence of the shadowing. Other sonographic appearances of fat necrosis include a complex mass with a mixed echo texture and an intracystic soft tissue mass. 13 lthough the sonographic findings may be quite alarming, the mammographic findings typically are benign appearing and suggestive of the diagnosis (Figure 6). The histologic appearance of fat necrosis similarly varies with the age of the process. Mass-forming lesions are characterized by lymphoplasmacytic inflammation, foamy macrophages, foreign bodytype giant cells, and reparative fibrosis. Postsurgical Scars fter a benign breast biopsy, the breast tissue usually heals without residual perceptible changes. For patients who undergo breast conservation therapy for cancer, there is an increased likelihood of distortion and scarring after surgery and radiation therapy. These findings may be confusing if the appropriate clinical history is not provided. Likewise, for patients who have undergone benign excisional biopsy, the changes seen on the mammogram are usually obvious given the appropriate clinical history, prior comparison films, and even the images from the needle localization procedure. In cases when the appropriate history is not available, a postsurgical scar may mimic a malignancy. t sonographic evaluation, an area of posterior acoustic shadowing may be seen. 1 It has been our experience that the shadowing associated with a scar often has shadowing without a central mass. This lack of a central mass helps differentiate a scar from a carcinoma, which has shadowing arising from a central mass. With scars, the degree of posterior acoustic shadowing may be more prominent in certain planes than in others, as in our example (Figure 7). Occasionally, on sonography a hypoechoic surgical plane margin may be seen extending from the surgical bed to the skin surface. years and speculated on a hormonal etiology. In fact, this process may have several causes, regional or partial mammary involution probably being the most common. 16 Figure 6. Fat necrosis in a 24-year-old woman with a palpable left breast mass. Directed breast sonography was initially performed, revealing several hypoechoic masses with posterior acoustic shadowing., Sonogram showing one of the masses., Mammogram showing several peripherally calcified masses, clearly consistent with fat necrosis. The patient did not recall a history of trauma. Careful correlation with limited mammographic imaging in this young woman helped clarify the exact etiology of the benign yet palpable breast changes. Focal Fibrosis Focal fibrosis is a fairly common condition, accounting for as many as 9% of lesions diagnosed on the basis of core needle biospy. 14 It was first described as a distinct entity by Haagensen, 15 who noted its occurrence during the reproductive 78 J Ultrasound Med 23:73 83, 2004

7 Weinstein et al Focal fibrosis manifests with a range of mammographic and sonographic findings. The mammographic findings include circumscribed masses, asymmetric densities, architectural distortion, and irregular masses. 14,17 Similarly, on sonography the appearance may vary from circumscribed hypoechoic masses to questionable hypoechoic masses with or without posterior acoustic shadowing and posterior acoustic shadowing without definite masses. 14,17 Examples of Figure 7. Postsurgical scar in a 57-year-old woman with a history of benign left breast biopsy. and, Sonograms of the scar site showing dense posterior acoustic shadowing. During dynamic scanning, no central mass was shown. The degree of posterior acoustic shadowing is more prominent in the antiradial direction () than in the radial position (). fibrosis are shown in Figures 8 and 9. Pathologic studies of this entity differ in only 1 respect: the character of the interface of the lesion with surrounding breast. Most describe the process as forming a clinically dominant mass that has microscopically indistinct margins; others say the mass is discrete and sharply circumscribed. 15,18 In fact, both configurations are seen, in parallel with the range of imaging features. Figure 8. Focal fibrosis in a 32-year-old woman with a palpable breast mass. The mammogram revealed dense breast tissue without a questionable focal abnormality., Directed sonogram over the palpable area of concern showing a hypoechoic region with posterior acoustic shadowing. Excisional biopsy was performed, revealing fibrosis., Pathologic examination revealed a discrete mass that was not grossly or microscopically visible; the tissue was composed of paucicellular fibrous tissue with completely atrophic parenchymal structures (original magnification 100). Some fat is evident at the edges of the resected tissue as well as in interposed wispy streaks and small pockets. J Ultrasound Med 23:73 83,

8 Posterior coustic Shadowing in enign reast Lesions y definition, the epithelial components of the fibrocystic change complex are absent. t pathologic evaluation the key features include dense stromal fibrosis with atrophy of ducts and lobules. variable amount of chronic inflammatory infiltrate may be present, composed of small lymphocytes. 13 Sclerosing denosis Sclerosing adenosis is a component of the proliferative fibrocystic change complex that is usually spotty but may coalesce to form a dominant mass on its own (so-called adenosis Figure 9. Focal fibrosis in an 87-year-old woman with a palpable mass in the left breast., Craniocaudal mammograms showing developing density (arrows) in the central breast, which was not seen on a mammogram obtained 2 years earlier (). C, Sonogram showing a poorly defined hypoechoic area with posterior acoustic shadowing. iopsy revealed fibrosis. D, Medium-power view showing dense fibrosis with bundles of collagen and bland spindled stromal cells (original magnification 100). There is a sparse chronic inflammatory infiltrate composed of small lymphocytes. C D 80 J Ultrasound Med 23:73 83, 2004

9 Weinstein et al tumor). It also may occur in the context of radial scars and sclerosing papillomas to create a highly complex imaging and pathologic picture. The condition typically manifests as a mammographic abnormality, although rarely it may manifest as a palpable breast finding. 19 The most common appearance on mammography is a focal group of punctate or amorphous calcifications or a regional cluster of powdery calcifications. However, sclerosing adenosis may also appear as a nodule or a spiculated mass. 20 lthough there is limited information on the sonographic evaluation of sclerosing adenosis, at sonography, posterior acoustic shadowing may be seen, 1,3 as shown in Figure 10. The shadowing may be due to the fibrotic response elicited by this entity. 3 t pathologic evaluation, closely packed benign lobules are seen, composed of distorted acini with surrounding fibrosis. The fibrotic stroma compresses, elongates, and distorts the acini. The normal 2-cell layer of the ductules is retained, although the myoepithelial cell layer is usually hyperplastic. 7 Normal reast Tissue Real-time sonographic evaluation of normal breast tissue may exhibit posterior acoustic shadowing. 1 ecause the ultrasonic transducer scans over the multiple tissue interfaces, such as Cooper ligaments and other connective tissue, posterior acoustic shadowing may result. However, on rescanning and dynamic imaging of the area, particularly in a different plane, the shadowing may resolve or may appear less prominent. dditionally, because the posterior acoustic shadowing is generated by interfaces, there should be no associated mass. This example shows the importance of dynamic real-time scanning in the evaluation of subtle breast lesions. Figure 11 shows shadowing as an artifact that may be seen in normal breast tissue. Figure 10. Sclerosing adenosis in a 45-year-old woman with an area of architectural distortion in the upper outer quadrant., Sonogram showing a vague hypoechoic area with posterior acoustic shadowing (arrows). The degree of posterior acoustic shadowing is not as dense as in carcinomas that have shadows. Wire localization biopsy showed irregularly fibrotic breast tissue without a discrete mass. and C, Microscopic specimens showing a complex combination of proliferative fibrocystic changes dominated by sclerosing adenosis and multiple microscopic radial scars forming confluent nodules and bands of dense fibrosis ( and C, respectively, original magnification 50). Sclerosing adenosis consists of a micronodular proliferation of small mammary acini with prominent spindling myoepithelial cells and fibrosis. The fibrotic stroma compresses, elongates, and distorts the acini. C J Ultrasound Med 23:73 83,

10 Posterior coustic Shadowing in enign reast Lesions Conclusions Sonography is an indispensable tool in the evaluation of breast abnormalities. Posterior acoustic shadowing is a sonographic characteristic that is most commonly associated with breast malignancies. However, it is important to keep in mind that this sonographic finding may also be seen in benign breast masses. The clinical history and mammographic findings, in conjunction with the sonographic findings, will often lead to the correct diagnosis. If core needle biopsy is performed on a lesion with posterior acoustic shadowing, it is important to keep in mind that a specific benign diagnosis, such as a fibroadenoma or diabetic mastopathy, may indeed be concordant with the imaging findings. Figure 11., Sonogram of normal breast tissue showing posterior acoustic shadowing., On reevaluation on the same area, the shadowing is no longer seen. References 1. Mendelson E. The breast. In: Rumack CM, Wilson SR, Charboneau JW (eds) Diagnostic Ultrasound. 2nd ed. St Louis, MO: CV Mosby Co; 1998: Stavros T, Thickman D, Rapp CL, Dennis M, Parker SH, Sisney G. Solid breast nodules: use of sonography to distinguish between benign and malignant lesions. Radiology 1995; 196: Kopans D. Pathologic, mammographic, and sonographic correlation. In: Kopans D (ed). reast Imaging. 2nd ed. Philadelphia, P: Lippincott-Raven; 1998: shton M, Lefkowitz M, Tavassoli F. Epithelioid stromal cells in lymphocytic mastitis: a source of confusion with invasive carcinoma. Mod Pathol 1994; 7: Feder JM, de Paredes ES, Hogge JP, Wilken JJ. Unusual breast lesions: radiologic-pathologic correlation. Radiographics 1999; 19:S11 S Tavassoli F Mesenchymal lesions. In: Tavassoli F (ed). Pathology of the reast. 2nd ed. New York, NY: ppleton & Lange; 1999: lleva DQ, Smetherman DH, Farr GH, Cederbom GJ. Radial scar of the breast: radiologic-pathologic correlation in 22 cases. Radiographics 1999; 19:S27 S Tavassoli F. enign lesions. In: Tavassoli F (ed) Pathology of the reast. 2nd ed. New York, NY: ppleton & Lange; 1999: Cohen M, Sferlazza SJ. Role of sonography in evaluation of radial scars of the breast. JR m J Roentgenol 2000; 174: Cardenosa G. Terminal duct. In: Cardenosa G (ed). reast Imaging Companion. 2nd ed. Philadelphia, P: Lippincott-Raven; 2001: Soler NG, Khardori R. Fibrous disease of the breast, thyroiditis and cheiroarthropathy in type I diabetes mellitus. Lancet 1984; 1: Weinstein SP, Conant EF, Orel SG, Lawton TJ, cs G. Diabetic mastopathy in men: imaging findings in 2 patients. Radiology 2001; 219: Cardenosa G. Stroma. In: Cardenosa G (ed). reast Imaging Companion. 2nd ed. Philadelphia, P: 82 J Ultrasound Med 23:73 83, 2004

11 Weinstein et al Lippincott-Raven; 2001: Rosen EL, Soo MS, entley RC. Focal fibrosis: a common breast lesion diagnosed at imaging-guided core biopsy. JR m J Roentgenol 1999; 173: Haagensen CD. Fibrous disease of the breast. In: Haagensen CD (ed). Diseases of the reast. 2nd ed. Philadelphia, P: W Saunders Co; 1971: Minkowitz S, Hedayati H, Hiller S, Gardner. Fibrous mastopathy: a clinical histopathologic study. Cancer 1973; 32: Revelon G, Sherman ME, Gatewood OM, rem RF. Focal fibrosis of the breast: imaging characteristics and histopathologic correlation. Radiology 2000; 216: Rosen PP. enign mesenchymal neoplasms. In: Rosen s reast Pathology. 2nd ed. Philadelphia, P: Lippincott Williams & Wilkins; 2001: Cardenosa G. Lobules. In: Cardenosa G (ed). reast Imaging Companion. 2nd ed. Philadelphia, P: Lippincott-Raven; 2001: Cyrlak D, Carpenter PM, Rawak N. reast imaging case of the day: florid sclerosing adenosis. Radiographics 1999; 19: J Ultrasound Med 23:73 83,