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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 between atypical ductal hyperplasia and carcinoma.
The reported prevalence of a radial scar is 0.1-2 per 1000 screening mammograms. Radial scars are very rare in women younger than 40 years and older than 60 years. They most often occur in women between 41-60 years 12,13.
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 is higher when there is associated atypia on histology.
Other associations include 4:
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 a radial extension of tubular structures (the spiculated peripheral borders), mimicking infiltrating carcinoma. This 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 a radial scar 11,12.
A radial scar has a spiculated appearance similar to carcinoma, but the center tends to be a translucent, low-density area rather than a mass. The breast tissue behind the lesion is almost visible through the lesion. The relatively low density of the center is a relevant and visible difference between carcinoma and a radial scar.
A carcinoma tends to have a dense center. With a radial scar there is no dense center; in fact, the lesion is usually as dense centrally as it is peripherally. There is no "attempt" at forming a mass in a radial scar.
The spicules running from the center are in general longer and gracile than those of a carcinoma, and 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 a radial scar.
Its mammographic appearance is also similar to a post-surgical breast scar and can vary markedly with differing projections (i.e. CC vs 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.
Features are replicated as described in the aforementioned modalities. There will be spiculation and architectural distortion. Non-enhancement of the lesion favors a benign process. Enhancement suggests an underlying malignancy.
Treatment and prognosis
A radial scar is considered a high-risk breast lesion and histological differentiation from associated carcinoma is required. FNA and core biopsies can underestimate the underlying associated malignancy and are controversial.
Historically, if a radial scar was revealed on biopsy, surgical excision was always recommended due to the possibility of a sampling error caused by the eccentric and marginal location of an invasive carcinoma present within the radial scar. Nowadays, according to recent international consensus, therapeutic excision with vacuum-assisted biopsy or excision (VAB or VAE) is advised as the next step. The goal of vacuum-assisted excision is to collect roughly 4 g of tissue to emulate a surgical biopsy without complications 14.
Differential considerations for mammographic appearances include:
a central mass tends to form; the spicules are shorter and thicker and there is retraction of the parenchyma
invasive lobular carcinoma results in a loss of E-cadherin and diffuse infiltration of the tumor cells, and can sometimes be impossible to distinguish from a radial scar
in practice, this is rarely if ever a source of confusion; it is extremely rare to find post-surgical scarring with spicules as long as a radial scar
you also have the history on the technologist notes, and if all else fails, the scar on the patient's skin