(Radiographics. 1999;19:S80-S83.)
© RSNA, 1999
Breast Imaging Case of the Day1
Dvora Cyrlak, MD and
Philip M. Carpenter, MD
1 From the Departments of Radiological Sciences (D.C.) and Pathology (P.M.C.), University of California, Irvine Medical Center, 101 The City Drive, Orange, CA 92868-3298. From the 1998 RSNA scientific assembly. Received February 19, 1999; revision requested March 3 and received April 8; accepted April 12. Address reprint requests to D.C.
Index Terms: Breast, calcification, 00.811 • Breast, diseases, 00.313, 00.48 • Fat, necrosis, 00.48
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HISTORY
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A 47-year-old woman presented for routine screening mammography. A lipid cyst had been demonstrated at mammography 3 years earlier.
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FINDINGS
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Initial mammography of the right breast had demonstrated a circumscribed area of lucency with a thin capsule, a finding that was compatible with a lipid cyst (Fig 1). Mammography performed 3 years later no longer demonstrated the lipid cyst but did show new, heterogeneous microcalcifications in the same area (Fig 2).
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Figure 1a. (a, b) Initial craniocaudal (a) and mediolateral oblique (b) mammograms of the right breast demonstrate a circumscribed area of lucency with a thin capsule in the upper outer quadrant (arrow), a finding that is compatible with a lipid cyst. (c) Magnified craniocaudal view of the area of interest shows the lipid cyst to better advantage.
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Figure 1b. (a, b) Initial craniocaudal (a) and mediolateral oblique (b) mammograms of the right breast demonstrate a circumscribed area of lucency with a thin capsule in the upper outer quadrant (arrow), a finding that is compatible with a lipid cyst. (c) Magnified craniocaudal view of the area of interest shows the lipid cyst to better advantage.
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Figure 1c. (a, b) Initial craniocaudal (a) and mediolateral oblique (b) mammograms of the right breast demonstrate a circumscribed area of lucency with a thin capsule in the upper outer quadrant (arrow), a finding that is compatible with a lipid cyst. (c) Magnified craniocaudal view of the area of interest shows the lipid cyst to better advantage.
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Figure 2a. (a, b) Craniocaudal (a) and mediolateral oblique (b) mammograms obtained 3 years after Figure 1 no longer show the lipid cyst. However, new heterogeneous microcalcifications are seen in the same area (arrow). (c) Coned compression magnification craniocaudal view demonstrates the calcifications more clearly.
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Figure 2b. (a, b) Craniocaudal (a) and mediolateral oblique (b) mammograms obtained 3 years after Figure 1 no longer show the lipid cyst. However, new heterogeneous microcalcifications are seen in the same area (arrow). (c) Coned compression magnification craniocaudal view demonstrates the calcifications more clearly.
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Figure 2c. (a, b) Craniocaudal (a) and mediolateral oblique (b) mammograms obtained 3 years after Figure 1 no longer show the lipid cyst. However, new heterogeneous microcalcifications are seen in the same area (arrow). (c) Coned compression magnification craniocaudal view demonstrates the calcifications more clearly.
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DIAGNOSIS: Fat necrosis of the breast.
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DISCUSSION
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Fat necrosis of the breast is a benign inflammatory process that may mimic malignancy clinically, mammographically, and sonographically. It was first described in 1920 by Lee and Adair (1), who reported two cases in which mastectomy was performed for clinically suspicious breast masses without prior biopsy. Fat necrosis is most common in obese, usually middle-aged women with fatty, pendulous breasts and most commonly occurs in a superficial (Fig 1) or periareolar portion of the breast (1–3). The most common causes of fat necrosis are surgery (biopsy, lumpectomy, reduction mammoplasty, implant removal, breast reconstruction) and radiation therapy (2–6). Another important cause is trauma, including blunt chest trauma (3,7), seat belt injury (8), and even minor trauma that the patient may not recollect (in our case, the patient remembered a "black and blue" mark that had "suddenly" developed 3 or 4 years earlier). Anticoagulant therapy with warfarin sodium (Coumadin) (9,10) and calciphylaxis (11) (hypersensitivity to local calcinosis associated with secondary hyperparathyroidism in renal failure) are very rare reported causes.
Typically, fat necrosis is clinically occult and is evident only at mammography (3); occasionally, however, single or multiple masses may be palpated at clinical examination. These masses may be tender or painless and smooth or irregular. Skin retraction, thickening, induration, and ecchymoses may also be present (3,12). In a setting of conservation therapy for breast cancer, the mass may develop in or near the excision scar (13).
The mammographic spectrum of fat necrosis ranges from clearly benign to indeterminate to malignant appearing masses or calcifications (3,12). Mammographically evident masses due to fat necrosis may be radiolucent with a thin, well-defined capsule, both radiolucent and dense with encapsulation (the "mycetoma" appearance) (4,14), dense and circumscribed, ill-defined, or even spiculated (5,6,12).
At ultrasonography, masses are most commonly solid, although they may be complex or cystic. Borders may be discrete or ill-defined. Posterior shadowing or enhancement may be present (15). Masses may be taller than wider (7). Distortion of surrounding architecture may also be present (15).
Calcifications seen at mammography may be clear-cut, benign rings, rims, or coarse macrocalcifications or may manifest as suspicious pleomorphic or even "branching type" microcalcifications (12). In patients with a history of lumpectomy and radiation therapy, calcifications due to posttherapy fat necrosis may manifest at mammography as clustered microcalcifications that are suspicious for malignancy (16).
The pathophysiology of fat necrosis helps explain its mammographic spectrum. At microscopic analysis, disruption of fat cells and hemorrhage with adjacent histiocytes is seen early in fat necrosis. Next, multinucleated histiocytes, lymphocytes, and plasma cells appear and hemosiderin is deposited. Necrotic fat and cellular debris are enclosed by peripherally developing fibrosis. Months or years later, the fibrosis contracts into a scar; the collection of oil or fat may remain (8,14). Older lesions tend to be less cellular and more fibrotic (13). Mammographic findings depend on the degree of fibrosis. Early, less extensive fibrosis is associated with a lipid cyst with a thin, fibrous capsule. With more extensive fibrosis, a spiculated mass that is indistinguishable from carcinoma may develop (8). Calcifications tend to be found in association with fibrosis and represent a relatively late finding (Fig 3). Early calcification of the fibrotic rim of a lipid cyst or collapse of a partially calcified lipid cyst may have an indeterminate mammographic appearance (3). Collapse of a partially calcified lipid cyst is the most likely explanation for the sequence of mammographic findings in the present case (Figs 1, 2).
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Figure 3. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) of a specimen obtained at stereotactically guided core needle biopsy demonstrates necrotic adipocytes centrally. The adipocytes lack cell nuclei and are surrounded by bands of fibrosis. Deeply basophilic calcium deposits are scattered throughout the fibrotic area.
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Although fat necrosis may mimic various manifestations of breast malignancy, needle localized biopsy and core biopsy have demonstrated this finding in only 1.9% and 2.5% of cases, respectively (3,17). In our case, results of stereotactically guided core needle biopsy confirmed the diagnosis of fat necrosis (Fig 3). Fat necrosis at core biopsy of a suspicious mass is considered a concordant finding as long as targeting is optimal and the fat necrosis is a discrete finding at pathologic analysis (17). With microcalcifications, the sensitivity of core biopsy is lower and scrupulous mammographic follow-up becomes crucial.
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Acknowledgments
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The authors thank Niraj B. Rawal, BS, for his assistance in the preparation of this manuscript.
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References
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HISTORY
FINDINGS
