DOI: 10.1148/rg.27si075510
RadioGraphics 2007;27:S37-S51
© RSNA, 2007
Breast Lesions Incidentally Detected with CT: What the General Radiologist Needs to Know1
Monica G. Harish, MD2,
Sheela D. Konda, MD, PhD2,
Heber MacMahon, MB, BCh, and
Gillian M. Newstead, MD
1 From the Department of Radiology, University of Chicago, 5841 S Maryland Ave, MC 2026, Chicago, IL 60637. Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received March 6, 2007; revision requested March 29 and received May 9; accepted May 16. H.M. is a stockholder in R2 Technology, consults for Riverain Medical and MEDIAN Technologies, and receives research support from R2 Technology, Mitsubishi Space Software, General Electric, and Eastman Kodak; G.M.N. is a member of the speakers bureau for Fuji Photo Film and the advisory board for Konica Minolta; all other authors have no financial relationships to disclose.
Address correspondence to S.D.K. (e-mail: Sheela.Konda{at}uchospitals.edu).
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Abstract
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Although breast abnormalities are frequently overlooked at multidetector computed tomography (CT) or inaccurately assessed, multidetector CT can reveal sufficient detail in many cases to allow confident diagnosis. It is important for general radiologists to characterize breast lesions incidentally found at CT as benign, indeterminate, or sufficiently suspicious to warrant further work-up. Irregular margins, irregular shape, and rim enhancement are the features most predictive of malignancy. Postoperative changes in the breast may mimic a malignancy; therefore, it is important to obtain an accurate history as to the timing of biopsy or surgery and to follow the changes in lesion morphology over time. Any mass with benign features at CT requires additional validation of benignity with demonstration of long-term stability or additional diagnostic mammographic work-up with or without sonographic evaluation. Accurate description and classification of breast lesions detected with CT enhance the value of the radiologist’s report and contribute to appropriate case management.
© RSNA, 2007
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LEARNING OBJECTIVES FOR TEST 1
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After reading this article and taking the test, the reader will be able to:
- Identify malignant and benign findings in the breast on CT scans.
- Describe the appearance of the breast at CT in the postoperative setting.
- Discuss how to accurately describe breast lesions incidentally found at CT.
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Introduction
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Mammography is currently the preferred examination for breast cancer screening; however, multidetector computed tomography (CT) often provides the first images of the breast when scanning is performed for pulmonary or cardiac disease. In addition, multidetector CT may provide further characterization of a breast lesion when performed in conjunction with mammography due to its improved contrast resolution, larger field of view, and cross-sectional capability (1,2). Breast lesions may be better imaged with multidetector CT compared with mammography if the breasts are dense (2) or if the lesion is located near the chest wall, and while the breasts are not the primary focus of most scans of the chest, abnormal findings are not uncommon (3,4).
Although dedicated breast imaging will often be required for definitive diagnosis (3), it remains important for the general radiologist to detect and characterize incidentally imaged breast lesions on CT scans as either clearly benign, indeterminate, or sufficiently suspicious as to warrant further work-up. The purpose of this article is to familiarize the reader with the CT appearance of a variety of breast abnormalities and to provide guidelines for interpretation of these lesions on the basis of the breast imaging lexicon that is used for other imaging modalities. The breast abnormalities presented are all larger than 1 cm in size, which is likely a reflection of the fact that the examinations reviewed were performed for other indications and the technology was not optimized for breast imaging. The breast lesions discussed were discovered incidentally, and there is a high likelihood that smaller breast lesions may have been overlooked.
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Malignant Breast Abnormalities
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Multidetector CT and dynamic contrast-enhanced techniques have been used to study features of malignancy in breast tumors (5–8). 
Irregular margins, irregular shape, and rim enhancement are the most highly predictive features for malignancy in these studies (6). A spiculated and irregular margin is the most accurate sign for malignancy (6,8). A washout pattern on postcontrast images had high positive predictive value and sensitivity, although low negative predictive value and specificity (8,9). Diffuse regional enhancement is also shown to have high positive predictive value for malignancy (10). CT also has the advantage of demonstrating the margin of tumor invasion without overlapping tissues, an added advantage over mammography (7). As is also true with breast magnetic resonance (MR) imaging, CT may allow identification of contralateral tumor when CT is performed for staging, with the added advantage of faster imaging and thinner collimation (3,5,7).
Invasive Ductal Carcinoma
Invasive ductal carcinoma is the most common breast cancer, accounting for about 80%–90% of all invasive cancers (11). The cancer usually grows as an irregular mass that is firm at palpation. Mammography may show a dense, spiculated mass sometimes with pleomorphic calcifications (12). There may also be adjacent pleomorphic calcifications representing ductal carcinoma in situ. The mass may be round, irregular, or spiculated at ultrasonography (US) (Fig 1). These cancers commonly produce acoustic shadowing due to fibrosis or tumor extension, although shadowing is not always present. At CT, invasive ductal carcinoma appears as a dense, spiculated mass with marked early and/or peripheral enhancement (Fig 2). The presence of rim enhancement and internal enhancing septations can be suggestive signs. In advanced cases, associated skin thickening, lymphadenopathy, or pleural effusions may be seen (Fig 3).
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Figure 1a. Invasive ductal carcinoma. (a–c) Axial (a) and coronal (b) nonenhanced CT scans and mediolateral mammogram of the left breast (c) show a spiculated, dense, ill-defined mass (arrow in c). (d) US image shows the hypoechoic mass with irregular margins and hypervascularity.
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Figure 1b. Invasive ductal carcinoma. (a–c) Axial (a) and coronal (b) nonenhanced CT scans and mediolateral mammogram of the left breast (c) show a spiculated, dense, ill-defined mass (arrow in c). (d) US image shows the hypoechoic mass with irregular margins and hypervascularity.
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Figure 1c. Invasive ductal carcinoma. (a–c) Axial (a) and coronal (b) nonenhanced CT scans and mediolateral mammogram of the left breast (c) show a spiculated, dense, ill-defined mass (arrow in c). (d) US image shows the hypoechoic mass with irregular margins and hypervascularity.
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Figure 1d. Invasive ductal carcinoma. (a–c) Axial (a) and coronal (b) nonenhanced CT scans and mediolateral mammogram of the left breast (c) show a spiculated, dense, ill-defined mass (arrow in c). (d) US image shows the hypoechoic mass with irregular margins and hypervascularity.
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Figure 2a. Invasive ductal carcinoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show a rim-enhancing irregular mass. (c) Craniocaudal mammogram of the right breast shows that the dense mass (arrow) is ill defined anteriorly.
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Figure 2b. Invasive ductal carcinoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show a rim-enhancing irregular mass. (c) Craniocaudal mammogram of the right breast shows that the dense mass (arrow) is ill defined anteriorly.
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Figure 2c. Invasive ductal carcinoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show a rim-enhancing irregular mass. (c) Craniocaudal mammogram of the right breast shows that the dense mass (arrow) is ill defined anteriorly.
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Figure 3a. Invasive ductal carcinoma. Axial (a) and coronal (b) contrast-enhanced CT scans and craniocaudal mammogram of the left breast (c) show a spiculated mass (arrow) with associated nipple retraction and skin thickening.
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Figure 3b. Invasive ductal carcinoma. Axial (a) and coronal (b) contrast-enhanced CT scans and craniocaudal mammogram of the left breast (c) show a spiculated mass (arrow) with associated nipple retraction and skin thickening.
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Figure 3c. Invasive ductal carcinoma. Axial (a) and coronal (b) contrast-enhanced CT scans and craniocaudal mammogram of the left breast (c) show a spiculated mass (arrow) with associated nipple retraction and skin thickening.
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Invasive Lobular Carcinoma
Invasive lobular carcinoma accounts for 10%–15% of invasive breast cancers. It spreads through the breast parenchyma by means of diffuse infiltration, which may cause little disruption of the underlying anatomic structures (11). The likelihood of bilaterality and multifocality is increased compared to invasive ductal cancers. The mammographic signs are often subtle. A discrete mass is less common than with other malignancies because the tumor may extend into surrounding tissue as a single line of cells. This infiltrative growth pattern may create only subtle architectural distortion at mammography. Microcalcifications are rarely present. CT findings may be non-specific, some cases appearing as an asymmetric soft-tissue density with or without associated skin thickening while others may manifest as a mass (Fig 4).
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Figure 4a. Invasive lobular carcinoma. (a–c) Serial axial contrast-enhanced CT scans, displayed from cranial (a) to caudal (c), show a diffusely infiltrating enhancing area of opacity without a discrete mass (arrow in b). The nodular density lateral to the breast with calcification is likely a benign finding. (d) Axial CT scan of the opposite breast, obtained at the same level as b, shows the subtle asymmetry.
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Figure 4b. Invasive lobular carcinoma. (a–c) Serial axial contrast-enhanced CT scans, displayed from cranial (a) to caudal (c), show a diffusely infiltrating enhancing area of opacity without a discrete mass (arrow in b). The nodular density lateral to the breast with calcification is likely a benign finding. (d) Axial CT scan of the opposite breast, obtained at the same level as b, shows the subtle asymmetry.
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Figure 4c. Invasive lobular carcinoma. (a–c) Serial axial contrast-enhanced CT scans, displayed from cranial (a) to caudal (c), show a diffusely infiltrating enhancing area of opacity without a discrete mass (arrow in b). The nodular density lateral to the breast with calcification is likely a benign finding. (d) Axial CT scan of the opposite breast, obtained at the same level as b, shows the subtle asymmetry.
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Figure 4d. Invasive lobular carcinoma. (a–c) Serial axial contrast-enhanced CT scans, displayed from cranial (a) to caudal (c), show a diffusely infiltrating enhancing area of opacity without a discrete mass (arrow in b). The nodular density lateral to the breast with calcification is likely a benign finding. (d) Axial CT scan of the opposite breast, obtained at the same level as b, shows the subtle asymmetry.
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Secondary Lymphoma of the Breast
Secondary lymphoma of the breast, a manifestation of lymphoma elsewhere in the body, is more common than primary lymphoma, although both are rare. Lymphadenopathy is the most common manifestation of secondary lymphoma involving the breast, seen on mammograms as large, round lymph nodes in the axilla with loss of the fatty hila (Fig 5) (4,11). Secondary breast lymphoma is usually caused by non-Hodgkin lymphomatous infiltration of breast tissue (4). It is a rare cause of an ill-defined mass that resembles invasive ductal cancer at mammography. The borders of the mass may be indistinct due to lymphomatous infiltration into surrounding glandular tissue. If a patient has a primary diagnosis of lymphoma elsewhere in the body and a new ill-defined breast mass, primary breast cancer should still be the leading diagnosis; however, secondary lymphoma should be considered as a differential possibility.
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Figure 5a. Secondary lymphoma of the breast. (a) Contrast-enhanced CT scan shows bilateral marked axillary adenopathy (arrows). (b, c) Bilateral mediolateral mammograms show large dense masses (arrow) in the right (b) and left (c) axillae. The masses are due to lymphadenopathy from secondary lymphoma. (d) Contrast-enhanced CT scan of another patient shows skin thickening with palpable large, irregular masses. The masses demonstrate poor enhancement because the image is from the arterial phase of a pulmonary embolus study.
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Figure 5b. Secondary lymphoma of the breast. (a) Contrast-enhanced CT scan shows bilateral marked axillary adenopathy (arrows). (b, c) Bilateral mediolateral mammograms show large dense masses (arrow) in the right (b) and left (c) axillae. The masses are due to lymphadenopathy from secondary lymphoma. (d) Contrast-enhanced CT scan of another patient shows skin thickening with palpable large, irregular masses. The masses demonstrate poor enhancement because the image is from the arterial phase of a pulmonary embolus study.
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Figure 5c. Secondary lymphoma of the breast. (a) Contrast-enhanced CT scan shows bilateral marked axillary adenopathy (arrows). (b, c) Bilateral mediolateral mammograms show large dense masses (arrow) in the right (b) and left (c) axillae. The masses are due to lymphadenopathy from secondary lymphoma. (d) Contrast-enhanced CT scan of another patient shows skin thickening with palpable large, irregular masses. The masses demonstrate poor enhancement because the image is from the arterial phase of a pulmonary embolus study.
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Figure 5d. Secondary lymphoma of the breast. (a) Contrast-enhanced CT scan shows bilateral marked axillary adenopathy (arrows). (b, c) Bilateral mediolateral mammograms show large dense masses (arrow) in the right (b) and left (c) axillae. The masses are due to lymphadenopathy from secondary lymphoma. (d) Contrast-enhanced CT scan of another patient shows skin thickening with palpable large, irregular masses. The masses demonstrate poor enhancement because the image is from the arterial phase of a pulmonary embolus study.
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Inflammatory Carcinoma
Inflammatory carcinoma is an uncommon, aggressive tumor with early dermal lymphatic invasion and poor prognosis. Clinical diagnosis is based on increased warmth, induration of breast skin, erysipeloid edge (peau d’orange), and nipple retraction. In some cases, inflammatory carcinoma may be indistinguishable from mastitis and abscess but fails to respond to antibiotics (11). Inflammatory carcinoma should be considered in the differential diagnosis when breast edema is accompanied by clinical signs of infection.
Mammography of inflammatory cancer reveals findings of breast edema (skin thickening, diffuse increased breast density, trabecular thickening), a breast mass, asymmetric focal density, microcalcifications, nipple retraction, or axillary adenopathy (Fig 6). The CT appearance is aggressive with marked skin thickening and peripheral enhancement (Fig 6). A discrete mass is often absent with inflammatory cancer (Fig 7). US shows findings of breast edema in 96% of cases, masses in 80%, and dilated lymphatic channels in 68% (Figs 6, 8) (11).
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Figure 6a. Inflammatory carcinoma. (a) Contrast-enhanced CT scan shows an irregular, peripherally enhancing, solid mass with associated skin thickening. (b, c) Craniocaudal mammogram of the right breast (b) and US image (c) show diffuse infiltrative disease.
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Figure 6b. Inflammatory carcinoma. (a) Contrast-enhanced CT scan shows an irregular, peripherally enhancing, solid mass with associated skin thickening. (b, c) Craniocaudal mammogram of the right breast (b) and US image (c) show diffuse infiltrative disease.
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Figure 6c. Inflammatory carcinoma. (a) Contrast-enhanced CT scan shows an irregular, peripherally enhancing, solid mass with associated skin thickening. (b, c) Craniocaudal mammogram of the right breast (b) and US image (c) show diffuse infiltrative disease.
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Figure 7a. Inflammatory carcinoma. (a, b) Contrast-enhanced CT scans (a obtained at a higher level than b) show an irregular, peripherally enhancing, encapsulated, fluid density mass with thick septa and adjacent skin thickening. (c, d) Mediolateral mammogram of the right breast (c) and US image (d) show concordant findings (arrows in c).
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Figure 7b. Inflammatory carcinoma. (a, b) Contrast-enhanced CT scans (a obtained at a higher level than b) show an irregular, peripherally enhancing, encapsulated, fluid density mass with thick septa and adjacent skin thickening. (c, d) Mediolateral mammogram of the right breast (c) and US image (d) show concordant findings (arrows in c).
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Figure 7c. Inflammatory carcinoma. (a, b) Contrast-enhanced CT scans (a obtained at a higher level than b) show an irregular, peripherally enhancing, encapsulated, fluid density mass with thick septa and adjacent skin thickening. (c, d) Mediolateral mammogram of the right breast (c) and US image (d) show concordant findings (arrows in c).
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Figure 7d. Inflammatory carcinoma. (a, b) Contrast-enhanced CT scans (a obtained at a higher level than b) show an irregular, peripherally enhancing, encapsulated, fluid density mass with thick septa and adjacent skin thickening. (c, d) Mediolateral mammogram of the right breast (c) and US image (d) show concordant findings (arrows in c).
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Figure 8a. Inflammatory carcinoma. (a) Contrast-enhanced CT scan shows a solid, irregular, lobular mass (arrows) with surrounding edema of the breast. (b) US image shows the complex, lobulated, echogenic mass against the background of the edematous breast.
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Figure 8b. Inflammatory carcinoma. (a) Contrast-enhanced CT scan shows a solid, irregular, lobular mass (arrows) with surrounding edema of the breast. (b) US image shows the complex, lobulated, echogenic mass against the background of the edematous breast.
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Postoperative Findings
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Many patients undergo CT after surgery or biopsy for staging of their cancer and/or to evaluate progression of disease. Postoperative changes in the breast may mimic a malignant appearance. It is often important to obtain an accurate history as to the timing of biopsy or surgery and to follow the change in lesion morphology over time. Other clues to evaluate postoperative findings include patient symptoms suggesting infection, such as fever, and surrounding surgical changes that may include clips from biopsy or axillary dissection. Abscess formation is uncommon in the postoperative setting.
Hematoma and Seroma
Breast hematomas and seromas can be seen after biopsy, trauma, or surgery (Fig 9). Their diagnosis can be made by correlating the finding to the clinical history. Immediately after surgery or biopsy, the surrounding edema may obscure a hematoma. Hematomas will become smaller over time and eventually resorb and therefore can be distinguished from other masses (Fig 10) (11). An abscess may have a similar appearance at CT, although a clinical history of a fever and an elevated white blood cell count may suggest the diagnosis. As a hematoma resolves, the blood-filled mass changes to serous fluid, forming a seroma. At CT, seromas appear as well-defined, relatively high-attenuation fluid collections. There may be associated calcifications, metallic clips, or air-fluid levels, along with peripheral enhancement after contrast material administration.
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Figure 9. Postoperative hematoma or seroma. Contrast-enhanced CT scan shows an irregular, peripherally enhancing mass with punctate foci of air (short arrows) and an air-fluid level (long arrow).
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Figure 10a. Postoperative hematoma or seroma. (a–c) Serial nonenhanced CT scans show a round postoperative fluid collection (a) that resolves over time (b), leaving a fibrous scar (c). (d) Corresponding craniocaudal mammogram of the right breast shows the irregular, spiculated, high-density mass (arrow) posterior to a linear scar marker.
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Figure 10b. Postoperative hematoma or seroma. (a–c) Serial nonenhanced CT scans show a round postoperative fluid collection (a) that resolves over time (b), leaving a fibrous scar (c). (d) Corresponding craniocaudal mammogram of the right breast shows the irregular, spiculated, high-density mass (arrow) posterior to a linear scar marker.
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Figure 10c. Postoperative hematoma or seroma. (a–c) Serial nonenhanced CT scans show a round postoperative fluid collection (a) that resolves over time (b), leaving a fibrous scar (c). (d) Corresponding craniocaudal mammogram of the right breast shows the irregular, spiculated, high-density mass (arrow) posterior to a linear scar marker.
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Figure 10d. Postoperative hematoma or seroma. (a–c) Serial nonenhanced CT scans show a round postoperative fluid collection (a) that resolves over time (b), leaving a fibrous scar (c). (d) Corresponding craniocaudal mammogram of the right breast shows the irregular, spiculated, high-density mass (arrow) posterior to a linear scar marker.
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Fibrous Scar
Mammograms of biopsy sites during the immediate postoperative period show air and fluid at the site of intervention. As a scar develops, these are absorbed and the surrounding glandular tissue is drawn to a central dense nidus of fibrous tissue (Fig 11). Mammograms show centrally dense spiculated masses with straightening of the surrounding Cooper ligaments and retraction of normal glandular tissue, similar to findings of cancer (Figs 11, 12) (11). In some patients, there is no dense central nidus but rather a focal architectural distortion (Fig 13).
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Figure 11a. Postoperative scar. (a) Nonenhanced CT scan shows a spiculated dense mass. (b) Corresponding craniocaudal mammogram of the right breast shows an area of architectural distortion (arrow) that corresponds to the site of surgical scarring.
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Figure 11b. Postoperative scar. (a) Nonenhanced CT scan shows a spiculated dense mass. (b) Corresponding craniocaudal mammogram of the right breast shows an area of architectural distortion (arrow) that corresponds to the site of surgical scarring.
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Figure 13a. Postoperative scar. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an isolated finding of a spiculated, dense mass. (c) Corresponding craniocaudal mammogram of the left breast shows architectural distortion and surgical clips (arrow) in the area of an earlier lumpectomy.
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Figure 13b. Postoperative scar. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an isolated finding of a spiculated, dense mass. (c) Corresponding craniocaudal mammogram of the left breast shows architectural distortion and surgical clips (arrow) in the area of an earlier lumpectomy.
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Figure 13c. Postoperative scar. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an isolated finding of a spiculated, dense mass. (c) Corresponding craniocaudal mammogram of the left breast shows architectural distortion and surgical clips (arrow) in the area of an earlier lumpectomy.
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If the scar can be shown to occupy a surgical site, then the spiculated appearance is not of concern. In differentiating a scar from cancer, correlating prior biopsy locations from the patient history, reviewing prior images, and noting linear scar markers in the locations of prior biopsy are very important. Masses not corresponding to a postbiopsy scar should be considered suspicious. In addition, any new tissue growth in a previously identified postoperative scar (particularly after cancer resection) should be viewed with suspicion.
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Benign Breast Abnormalities
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Only a few studies have been conducted that investigate reliable indicators of malignancy at breast CT (6,8,9). However, we found no studies that describe features of breast lesions that have a high positive predictive value for benignity on CT scans. Therefore, the absence of malignant features at CT, as described earlier, and familiarity with characteristics of benign masses and calcifications at mammography and benign masses at MR imaging are currently the sole bases for recognizing benign breast lesions at CT. Therefore, until additional studies are conducted, any mass with benign features at CT requires additional validation of benignity with either demonstration of long-term stability and/or additional diagnostic mammographic work-up with or without sonographic evaluation.
Fibroadenoma
Fibroadenoma is the most common benign breast tumor. These benign lesions are most commonly found in women ranging from 15 to 40 years of age and are caused by proliferation of connective tissue within the lobule (13). Multiple fibroadenomas are present in 20% of cases (3). At CT, fibroadenomas appear as circumscribed, round or oval masses (Fig 14) that may demonstrate coarse popcornlike calcifications. Nonenhancing fibrous septations are a specific feature seen in some fibroadenomas at MR imaging; however, this has not yet been confirmed as an imaging characteristic at CT.
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Figure 14a. Biopsy-proved fibroadenoma. (a) Contrast-enhanced CT scan shows an elliptical, well-defined, homogeneously enhancing mass without associated nipple retraction or skin thickening. (b) Craniocaudal mammogram of the left breast shows the circumscribed, lobulated, noncalcified mass (arrow). Postsurgical changes and surgical clips are seen in the retroareolar region. (c) US image shows the solid, circumscribed, parallel, hypoechoic mass.
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Figure 14b. Biopsy-proved fibroadenoma. (a) Contrast-enhanced CT scan shows an elliptical, well-defined, homogeneously enhancing mass without associated nipple retraction or skin thickening. (b) Craniocaudal mammogram of the left breast shows the circumscribed, lobulated, noncalcified mass (arrow). Postsurgical changes and surgical clips are seen in the retroareolar region. (c) US image shows the solid, circumscribed, parallel, hypoechoic mass.
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Figure 14c. Biopsy-proved fibroadenoma. (a) Contrast-enhanced CT scan shows an elliptical, well-defined, homogeneously enhancing mass without associated nipple retraction or skin thickening. (b) Craniocaudal mammogram of the left breast shows the circumscribed, lobulated, noncalcified mass (arrow). Postsurgical changes and surgical clips are seen in the retroareolar region. (c) US image shows the solid, circumscribed, parallel, hypoechoic mass.
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Fibroadenolipoma
Fibroadenolipoma (hamartoma) is an uncommon, often palpable tumor that contains fat and glandular tissue and is often referred to as a "breast within a breast." At CT, fibroadenolipomas appear as a circumscribed, mixed-density lesion that contains macroscopic fat (Fig 15) (12).
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Figure 15a. Fibroadenolipoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an oval, circumscribed mass of mixed soft-tissue and fat density. (c) Craniocaudal mammogram of the right breast shows the fat and soft-tissue density mass with sharply defined margins.
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Figure 15b. Fibroadenolipoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an oval, circumscribed mass of mixed soft-tissue and fat density. (c) Craniocaudal mammogram of the right breast shows the fat and soft-tissue density mass with sharply defined margins.
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Figure 15c. Fibroadenolipoma. (a, b) Axial (a) and coronal (b) contrast-enhanced CT scans show an oval, circumscribed mass of mixed soft-tissue and fat density. (c) Craniocaudal mammogram of the right breast shows the fat and soft-tissue density mass with sharply defined margins.
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Benign Calcifications
Calcifications are an important and common finding in breast tissue. Calcifications can appear with or without an associated lesion, and their morphologies and distribution provide clues as to their cause. Typically, benign calcifications include lucent-centered calcifications, eggshell or rim calcifications, coarse or popcornlike calcifications, large rodlike calcifications, and round calcifications.
In general, larger round or oval calcifications that are uniform in size and shape have a higher probability of being associated with a benign process, whereas smaller, irregular, polymorphic, clustered calcifications heterogeneous in size and morphology are more often associated with a malignant process. Nearly all calcifications currently seen at CT are benign, on the basis of size alone, due to the limited spatial resolution (Fig 16). Uniform large, round calcifications are more likely benign, whereas fine pleomorphic calcifications smaller than 0.5 mm have a higher probability of indicating malignancy and are rarely visualized at CT (11,14). However, as technology advances and spatial resolution improves, malignant calcifications may be visualized more commonly on CT scans in the near future.
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Figure 16a. Benign calcifications. (a–c) Axial (a, b) and coronal (c) contrast-enhanced CT scans show multiple coarse benign-appearing calcifications. (The calcifications shown in a and b are in the same breast. The one shown in a is more lateral; the one shown in b is more medial.) (d) Craniocaudal mammogram of the right breast shows several popcorn calcifications, which are consistent with hyalinized fibroadenomas.
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Figure 16b. Benign calcifications. (a–c) Axial (a, b) and coronal (c) contrast-enhanced CT scans show multiple coarse benign-appearing calcifications. (The calcifications shown in a and b are in the same breast. The one shown in a is more lateral; the one shown in b is more medial.) (d) Craniocaudal mammogram of the right breast shows several popcorn calcifications, which are consistent with hyalinized fibroadenomas.
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Figure 16c. Benign calcifications. (a–c) Axial (a, b) and coronal (c) contrast-enhanced CT scans show multiple coarse benign-appearing calcifications. (The calcifications shown in a and b are in the same breast. The one shown in a is more lateral; the one shown in b is more medial.) (d) Craniocaudal mammogram of the right breast shows several popcorn calcifications, which are consistent with hyalinized fibroadenomas.
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Figure 16d. Benign calcifications. (a–c) Axial (a, b) and coronal (c) contrast-enhanced CT scans show multiple coarse benign-appearing calcifications. (The calcifications shown in a and b are in the same breast. The one shown in a is more lateral; the one shown in b is more medial.) (d) Craniocaudal mammogram of the right breast shows several popcorn calcifications, which are consistent with hyalinized fibroadenomas.
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Lactating Breast
Because postpartum and pregnant women are normally healthy, they require CT examinations in very few cases, such as evaluation for pulmonary emboli. Therefore, the general radiologist has little exposure to the appearance of lactating breasts on a CT scan. The postpartum breast demonstrates diffuse engorgement due to a sudden increase in milk volume and lymphatic and vascular congestion (Fig 17). At CT, lactating breasts show enlarged glands with bilateral cord-and masslike hyperattenuating tissue (15).
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Figure 17. Lactating breasts. Axial contrast-enhanced CT scan shows symmetric hyperattenuating, linear soft-tissue densities in both breasts, an appearance consistent with engorged lactiferous glands.
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Breast CT Lexicon
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Accurate assessment of breast lesions requires standardized terminology to describe and categorize abnormal findings. For mammography, breast US, and breast MR imaging, the Breast Imaging Reporting and Data System lexicon of the American College of Radiology provides the framework for standardized interpretation (16,17). Similarly, breast lesions detected with multidetector CT should be described by using a similar lexicon for succinct and accurate reporting.
After description of the shape (round, oval, lobular, irregular) and margins (circumscribed, microlobulated, obscured, indistinct, spiculated) of the breast mass at CT, findings should be classified according to density in Hounsfield units and categorized as either fat, air, fluid, or soft tissue (Fig 18). If contrast material was administered, the pattern of enhancement should be further characterized if possible as homogeneous, heterogeneous, rim enhancing, central enhancement, or enhancing internal septations (Fig 19). It is important to describe associated findings, as they will help in further characterizing a malignant or benign process. These include edema, skin retraction, nipple retraction, skin thickening (Fig 20), lymphadenopathy, chest wall or skin invasion, presence of a hematoma or blood, architectural distortion, and stability of findings compared to previous CT scans. In summary, accurate assessment of breast lesions at CT includes characterization of the shape, density, pattern of enhancement, and associated findings.
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