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Radial scar (RS) is a well-recognized radiological and pathological benign breast entity with specific characteristics. Generally, the term RS is assigned to such lesions less than 1 cm in diameter, whilst those that are 1 cm or larger are described as complex sclerosing lesions.
Post-mortem studies in the past had revealed the common presence of these lesions in the population, particularly in association with benign breast disease. Despite this, it is only in recent years that the clinical relevance of these lesions has come into prominence, due to the advent of population-based mammographic screening. Whilst RS are ordinarily defined as benign lesions, there is a growing body of evidence which suggests that they show an association with higher risk lesions (atypia and/or malignant changes) and may even be an independent risk factor for the growth of carcinoma in breast tissue.
With this said, there is much conflicting evidence for such associations. Some studies have found that the presence of RS increases the risk of breast cancer, while other studies fail to bring out such an association. One explanation is that radial scars are typically found alongside other breast conditions, which may have resulted in these mixed and perhaps misleading findings. Thus, there existence of a causal relationship between RS and breast cancer is yet to be conclusively determined.
RS are not actually scars, but areas of hardened breast tissue which may distort the normal tissue structure. Most women do not notice any RS-associated symptoms such as palpable lesions, or skin changes (thickening and retraction), unlike in the case of a carcinoma. Due to this, the detection of RS is often an incidental finding during a routine mammogram or investigation for an unrelated breast condition. About a fourth of RS may, however, be palpable.
Mammography may reveal typical though unspecific signs associated with RS. First, RS present as idiopathic and stellate (star-shaped) lesions which are apparently unrelated to surgery or trauma. Though their appearance may be similar to that of a carcinoma, they lack the characteristic dense centre. Instead, an RS shows central radiolucency, because of the fibroelastotic central zone. This tends to be a translucent, low-density area rather than a mass. In fact, the breast tissue beneath the lesion is nearly visible through the lesion which exhibits the same low density centrally and peripherally. This characteristic low central density is an important distinguishing factor between the RS and a carcinoma. The periphery of the lesion consists of long thin spicules (tubular structures) which radiate from the centre, and are in general longer and thinner than those associated with a carcinoma. Together, these characteristics give the lesion the appearance of a dark star.
Despite the fact that RS are generally considered benign lesions, they often present suspicious imaging features that mimic carcinoma. Furthermore, since RS can present with a variety of mammographic characteristics, a mammography should be considered rather as a pre-biopsy diagnostic tool. Detection of RS should be followed by the suggestion of an imaging-guided core needle biopsy (CNB) to exclude the possibility of malignancy. Once the biopsy sample has been examined by a pathologist, surgical excision of these lesions may be advised in order to exclude the possibility of a high-risk lesion (atypia or malignant) that was not detected by the procedure.