Radial scar, or complex sclerosing lesion, is a rosette-like proliferative breast lesion. It is not related to surgical scarring. Some authors however reserve the latter term to lesions over 1 cm 5.
It is an idiopathic process with sclerosing ductal hyperplasia.
Its significance is that it is a mimicker of scirrhous breast carcinoma. Although some classical differential descriptions exist (see below), these cannot be relied on, and the diagnosis must not be made on radiological features alone. Furthermore, there is an association with atypical ductal hyperplasia and carcinoma.
The reported prevalence of radial scars is 0.1-2.0 per 1,000 screening mammograms. Radial scar is very rare in women younger than 40 years and older than 60. Most often in women between 41-60 12-13 .
They are usually not palpable. Clinical examination of the breast containing regions of radial scar is often normal, although in about 25% of cases radial scars can be palpable. They do not cause skin thickening or retraction. Lesions are usually small and detected by mammography when they are at least 5 mm in size. Lesions <1 cm are called radial scars, while larger ones are often referred to as complex or radial sclerosing lesions.
A radial scar is a benign hyperplastic proliferative disease of the breast. Proposed possible causes include localized inflammatory reaction and chronic ischemia with subsequent slow infarction.
Histopathologically radial scars contain hyperplastic tissue cells and a central fibrous core, with radial extension of tubular structures (the spiculated peripheral borders), mimicking infiltrating carcinoma. These tubular formation has two rows of cells, epithelial and myoepithelial 9-10. The malignant potential is two times greater than in the normal population without radial scar 11-12.
In approximately 30% of cases, a radial scar is associated with ductal carcinoma in situ and tubular carcinoma of the breast. The occurrence of these are higher when there is associated atypia on histology.
Other associations include 4:
A radial scar has a spiculated appearance similar to carcinoma, but the centre tends be a translucent, low density area rather than a mass. The breast tissue behind the lesion is almost visible through the lesion. The relative low density of the centre is an important and visible difference between carcinoma and a radial scar.
A carcinoma tends to have a dense centre. With the radial scar there is no dense centre; in fact, the lesion is usually as dense centrally as peripherally. There is no "attempt" at forming a mass in a radial scar.
The spicules running from the centre are in general longer and gracile than those of a carcinoma (look at the image in Case 1 and 2 thoughtfully. These are representative images).
The spicules are described as long and thin with radiating radiolucent linear structures, which against a radiolucent fat background gives a black star or dark star appearance 6. Microcalcifications are possible but rare in a radial scar. However, unlike a carcinoma, features such as skin thickening and retraction are characteristically absent 2. There is no visible scirrhous reaction in the radial scar.
Its mammographic appearance is also similar to a post-surgical breast scar, and can vary markedly with differing projections (i.e. CC versus MLO).
On ultrasound, a radial scar is often ill-defined and disturbs the architecture of surrounding breast parenchyma. The lesion is usually round, oval or lobulated. Variable internal echoes can be found. Some radial scars show retro-acoustic attenuation.
Treatment and prognosis
A radial scar is considered a high risk breast lesion and histological differentiation from associatied carcinoma is required. FNA and core biopsies can underestimate the underlying associated malignancy and are controversial. The lesions are biopsied and removed.
Differential considerations for mammographic appearances include:
- breast cancer: a central mass tends to form. The spicules are shorter and thicker and there is retraction of the parenchyma; however sometimes the invasive lobular carcinoma, due to lack of the E-cadherin and diffuse infiltration of the tumours cells, it can be impossible to distinguish it from radial scar
- post-surgical breast scar: in practice this is rarely if ever a source of confusion. Its really rare to find post-surgical scarring with such long spicules as a radial scar and you also have the history on the technologist notes and if all else fails, the scar on the patient's skin
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