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Radial Scar


The term radial scar (RS) was first coined in the 1980s in a German paper by Hamperl. Page and Anderson first suggested using the term radial scar for lesions measuring up to 9 mm and the term complex sclerosing lesion (CSL) for larger lesions. Sloane and Mayers used a 10-mm cutoff for RS and CSL for larger lesions. However, one of the earliest published reports described a lesion as rosettes or proliferation centers, which corresponded to the currently most accepted term of RS . The earliest probable description of RS was in the 1940s by Bloodgood. In the 1970s and later, more attention was paid to these lesions, perhaps due to widespread use of screening mammography. Other terms that have been used include sclerosing papillary proliferation , nonencapsulated sclerosing lesion , infiltrating epitheliosis and benign sclerosing ductal proliferation . Rosen preferred the term radial sclerosing lesion as an all-encompassing descriptive name for these lesions, which show essentially the same overall histological characteristics irrespective of their size. In this chapter, the term RS is used in a general sense for both RSs and CSLs because this term is well accepted and used in both the pathology and the radiology literature.

There are differing views regarding the possible pathogenesis of RSs. Hamperl suggested that an RS is formed by the pulling or entrapment of proliferating ducts into a focus of sclerosis. Andersen and Gram postulated that it is a reaction to trauma with resulting fibrosis and elastosis. Others suggested that RS is a proliferative breast disease as RSs were more commonly found in breasts with fibrocystic changes. In general, most studies focused on the resemblance and association of an RS with premalignant and malignant breast lesions.

The incidence of RSs is difficult to establish from the published literature. Based on breast screening programs including mammography-based screening data, the incidence was approximately 0.1 to 9 per 1,000 screening mammograms. Other screening mammography-based databases show a true increase in recognition of RS in imaging studies, reporting an incidence of approximately 3 to 9 per 1000 mammograms. Conversely, concurrent pathology literature reported a much higher incidence of 1.7% to 28%. The initial pathology literature comprised population-based autopsy series, which probably overestimated the incidence; studies using large population-based cohorts reported an incidence of 4.7% to 7.1 % based on the Nurses’ Health Study, the Nashville Breast Cohort, and the Mayo Clinic Benign Breast Disease Cohort, and these figures most likely represent a relatively true incidence of RS. Recent data indicate that breast tomosynthesis will enhance the detection of an RS.

An RS can mimic invasive carcinoma in both imaging and histology. Therefore, all stellate lesions detected by imaging lead to biopsy. In histological sections, an RS may be the explanation of a radiological spiculated lesion or it may be an incidental finding. An incomplete or partial sampling of an RS, which is often the case in percutaneous core needle biopsy, can pose significant diagnostic challenges. Following are discussions on the microscopic differential diagnosis of RS and an overview of imaging and clinical management of RSs.

Radial Scar

Clinical Presentation

An RS is often subclinical, particularly when it is 5 mm or less in size, but it is increasingly detected with the routine use of more sensitive digital mammography for screening. The characteristic radiological appearance is that of a stellate lesion mimicking invasive carcinoma. In most cases, its presence leads to classification of the mammogram as at least indeterminate or suspicious; that is, Breast Imaging Reporting & Data System (BI-RADS) classification 3 or 4.

The incidence of an RS in imaging studies is difficult to assess in the literature, owing to a change in the mammographic modality from analog to digital. The volume and demographics of the screening population can also affect RS detection rates. However, in the pathology literature the reported incidence varies from a 2-3 percent up to 63% in both benign breast specimens and those containing invasive carcinoma. There is also some confusion regarding the precancerous potential of RS and its direct association with noninvasive and invasive carcinomas. It is reasonable to say that the distribution of an RS is similar in breasts with or without carcinoma.

Clinical Imaging

On mammogram, an RS appears as a stellate lesion with opacity of the central zone, radiating spicules, absence of calcifications, and varying appearance on different projections. The presence of a translucent center and elongated radiating spicules favors an interpretation of an RS, while in contrast, invasive cancers tend to show dense central regions and shorter and relatively straight projections ( Fig. 16.1 ). However, these features are not totally reliable; thus nearly all mammographic stellate lesions are classified as BI-RADS 3 or higher, and a needle biopsy is suggested as the first step in the diagnostic workup.

Fig. 16.1, Mammographic features of a radial scar (RS). ( A ) An RS presents as a stellate lesion (circle) with indistinct borders interdigitating with surrounding fat in the mediolateral view. The center is often translucent but opacity may be seen, as shown here. ( B ) A higher-magnification view shows a heterogeneous center with both density and lucency. Note that the spicules are elongated and of variable length rather than short, as is often the case in invasive cancers. ( C ) This stellate lesion, well developed and measuring larger than 10 mm in craniocaudal view, represents an example of a complex sclerosing lesion. The center is relatively homogeneous and dense and the spicules are long and irregular. ( D ) The stellate lesion of an RS can mimic carcinoma to perfection.

The ultrasound features of RS overlap with those of invasive tumor (i.e., irregular hypoechoic mass with ill-defined borders and posterior acoustic shadowing; Fig. 16.2 ).

Fig. 16.2, Ultrasound features of a radial scar (RS) versus invasive cancer. ( A ) This hypoechoic mass is taller than it is wide with very irregular borders. No internal heterogeneity in echotexture is seen. There is prominent shadowing underneath the lesion. ( B ) Invasive cancer shares several sonographic features with RS, such as irregular borders and shadowing. However, in contrast, the irregular edges are short and stubby, thus giving a more rounded appearance. There is often heterogeneous echoing in invasive cancer with a few calcifications, which appear as intense white areas.

Some radiographers find it easier to visualize an RS on ultrasound than on mammogram. Parenchymal distortion in the absence of a hypoechoic mass is also considered a useful sonographic feature that favors a diagnosis of RS. Other features, such as presence of an echogenic halo, sound attenuation, cysts at the periphery, and complex echotexture, are also seen more often with RSs than with invasive cancers.

In breast magnetic resonance imaging (MRI), features favoring an RS over an invasive cancer include ill-defined lesions without clearly spiculated margins, a homogeneous contrast enhancement pattern, and slow rates of contrast pickup with a continuous increase in intensity without a plateau.

Key Clinical Features

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