Invasive Ductal Carcinoma. Invasive ductal carcinoma is the most common breast cancer and accounts for approximate- ly 90% of all cancers. Also known as invasive ductal carcinoma not otherwise specified (NOS), invasive ductal carcinoma usu- ally grows as a hard irregular mass in the breast (Fig. 4.30; Video 4.10). The classic appearance of invasive ductal carcinoma is a high-density irregular or spiculated mass, occasionally contain- ing or associated with adjacent pleomorphic calcifications repre- senting DCIS. On the mammogram, the mass should be about the same size and density on two orthogonal mammographic views.
Spot compression magnification views may show unsuspected calcifications in or around the mass or unsuspected irregular borders.
Mammographic spiculated masses are often round, irregular, or spiculated on US and commonly produce acoustic shadow- ing as a result of either productive fibrosis or tumor extension.
When present, acoustic spiculation looks like thin radiating lines extending from the tumor into surrounding breast structures, occasionally causing tissue distortion. In a dense white breast, the US spicules are dark against the white glandular tissue.
In a fatty breast, the spicules are white against the dark fatty background.
On MRI, the usual appearance of invasive ductal cancer is a brightly enhancing irregular mass with or without spiculation;
enhancement is initially rapid, with a late-phase plateau or wash- out curve. Rim enhancement and heterogeneous enhancement are other worrisome signs for invasive ductal cancer on MRI.
Invasive Lobular Carcinoma. Invasive lobular carcinoma (ILC) is most commonly seen as an equal-density or high-density noncalcified mass, occasionally showing spiculations or ill-de- fined borders (Fig. 4.31; see also Fig. 4.1). Johnson et al. (2015) and Hilleren et al. (1991) showed that 50% of ILC may have a density equal or lower than surrounding glandular tissue and Mendelson et al. (1989) showed that some ILC may contain lu- cent areas. ILC has a higher rate of bilaterality and multifocality than does invasive ductal cancer. It accounts for less than 10%
of all invasive cancers, but historically it is the most difficult BOX 4.3 Ultrasound Features of Solid Breast
Masses: Malignant versus Benign MALIGNANT
Irregular shape
Not-parallel orientation (taller than wide)
Not-circumscribed margin (indistinct, angulated, microlobulated, and spiculated)
Very hypoechoic Acoustic shadowing Microcalcifications Duct extension Branch pattern
Hard elasticity assessment BENIGN
Oval shape
Parallel orientation (wider than tall) Circumscribed margin
Intense homogeneous hyperechogenicity Four or fewer gentle lobulations
Thin echogenic pseudocapsule/ellipsoid shape No malignant characteristics
Modified from Stavros AT, Thickman D, Rapp CL, et al: Solid breast nodules: use of sonography to distinguish between benign and malignant lesions, Radiology 196:123–134, 1995.
BOX 4.4 American College of Radiology Recom- mendations for Breast Ultrasound Labelinga Right or left breast
Mass position in terms of clock face or quadrant Number of centimeters from the nipple
Scan plane (radial/antiradial and transverse/long) Initials of person performing the scan
Orthogonal images of mass without and with measuring calipers
a2014 ACR Practice Parameter for the Performance of the Breast Ultrasound Ex- amination
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breast cancer to see on mammograms (Box 4.7). ILC gives radi- ologists a bad name because it can be missed by mammography, at a rate reported by Brem et al. (2009) to be as high as 21%. This failure can be partly explained by the growth pattern of the carcinoma. Classically, ILC grows in single lines of tumor cells infiltrating the surrounding glandular tissue and may not pro- duce a mass, making it difficult to see by mammography and dif- ficult to feel by physical examination. It usually does not contain microcalcifications. It often infiltrates the breast, is often seen on only one view, and may cause only subtle distortion of the
surrounding glandular tissue. When actually seen on the mam- mogram, ILC masses are often of equal or higher density than fibroglandular tissue and are seen because of the mass itself or its effect on surrounding tissue, such as architectural distortion and straightening of Cooper’s ligaments. As with any mass, dis- tortion, flattening, and tenting of glandular tissue caused by ILC are most easily seen in locations in which Cooper’s ligaments extend out into surrounding fat, such as in the retroglandular fat or along the edge of the normal, scalloped fibroglandular tissue (see Figs. 4.10 and 4.25).
A
C B
FIG. 4.29 Ultrasound (US)-guided marker placement to correlate nonpalpable US and mammography findings.
(A) A patient with a nonpalpable mass seen only on the mediolateral oblique (MLO) view underwent US, showing an indistinct, not-parallel mass with an echogenic rim and acoustic shadowing. (B) After US-guided core biopsy with marker placement in the mass, a BB skin marker was placed over the skin where US showed the mass. (C) The MLO view shows the mass and marker (arrow) and the skin BB over the mass, proving the US-detected find- ing represents mammographic mass. Biopsy showed invasive ductal carcinoma. Note the metallic linear scar marker on the skin over a previous biopsy.
BOX 4.5 American College of Radiology Breast Imaging Reporting and Data System Mass Reporting Size and location
Mass type and modifiers (shape, margin, and density) Associated calcifications
Associated findings
How changed if previously present Summary and BI-RADS code (0–6)
BI-RADS, Breast Imaging Reporting and Data System.
From American College of Radiology: ACR BI-RADS®—Mammography. In ACR BI-RADS atlas, breast imaging reporting and data system, ed 5, Reston, VA, 2013, American College of Radiology.
BOX 4.6 Differential Diagnosis of Spiculated Masses
Invasive ductal carcinoma Invasive lobular carcinoma Tubular cancer
Postbiopsy scar Radial scar
Fat necrosis (atypical) Sclerosing adenosis
Proliferative fibrocystic change (rare)
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On US, ILC is a hypoechoic, irregular, spiculated, or ill-defined mass that may or may not have acoustic shadowing. When ILC becomes very large, only the acoustic shadowing may be appar- ent; the mass itself can be difficult to see because of its large size. On MRI, ILC looks like a spiculated mass but may have vari- able enhancing patterns; it can look like a mass, like a distortion
of tissue, or like nodular regions connected by strands of tis- sue. Its enhancement kinetics can be similar to those of nor- mal breast tissue and can thus be a cause of false-negative MRI examinations. However, ILC is detected more readily by MRI compared with mammography and US, rendering ILC a com- mon indication for breast MRI when assessing extent of disease.
In a 2015 study, Debald et al. (2015) showed that women with ILC were significantly associated with having other foci of can- cer in the involved breast when evaluated with MRI (p = 0.02).
Tubular Carcinoma. Tubular carcinoma is a generally slow- growing tumor with a bilateral incidence of 12% to 40%. On mammography, tubular cancer is a dense or equal-density spicu- lated mass with occasional microcalcifications (Fig. 4.32). On oc- casion it may be apparent on the previous mammogram because of its slow growth. Although controversial, some pathologists be- lieve that radial scars may be a precursor to tubular carcinoma.
Generally, tubular carcinoma has a good prognosis and a lower
LOGIQ E9
A B C
FIG. 4.30 Spiculated mass: invasive ductal carcinoma. (A) Magnification craniocaudal (CC) mammogram shows a spiculated mass. (B) Tomosynthesis of left CC projection slice (see also Video 4.10) shows spiculations and mi- crocalcifications within the mass more clearly. (C) The corresponding ultrasound shows a hypoechoic mass with indistinct, spiculated margins. Biopsy showed invasive ductal carcinoma.
A B
FIG. 4.31 Spiculated mass: invasive lobular cancer in two different cases. (A) Spot compression craniocaudal mammogram shows a spiculated mass causing distortion (arrow) and flattening of the nipple. Thin straight lines extend from the tumor into subcutaneous fat, indicating its presence. (B) In another patient, there is a spiculated mass (arrow) at the edge of the film at the chest wall on a right mediolateral oblique view. The cancer looks very similar to the rest of the breast tissue and is seen only because of the spiculations extending into the fat, and also because it is a density in “no man’s land” in which there is usually only fat near the chest wall.
BOX 4.7 Features of Invasive Lobular Carcinoma 10% of all breast cancers
Grows in single-cell files
Hardest tumor to see on mammography Often seen on one view
Causes mass or architectural distortion Calcifications not a feature
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incidence of metastases than does invasive ductal cancer. On US, tubular cancers are hypoechoic, irregular masses that occasion- ally produce acoustic shadowing.