Discussion
Architectural distortion –
The breast is a modified skin gland that develops between two layers of the superficial fascia that splits to contain it. It is enveloped by the subcutaneous and the retromammary fat and covered by skin. Blood vessels, nerves and lymphatics are penetrating the fascial layers and the fatty envelope, to reach the skin on one side and the pectoralis muscle on the other. – The breast is attached to the chest wall by its sternal and its clavicular margins, allowing upward and medial displacement and limiting downward and lateral movements. – The breast itself and the glandular tissue, the main component of the breast, are divided into incomplete compartments, by strands of fibrous tissue, described by Cooper more than 150 years ago. These fibrotic planes are the ones that determine the shape of the breast and the distribution of the lobular divisions of the glandular tissue. The extreme variability of the fibrotic structure and subsequently the distribution of the glandular tissue between these planes make mammographic pictures so difficult to interpret. The fibrotic strands of tissue are running from the chest wall to converge at the nipple, being interconnected by secondary branches on their way. At all levels, this fibrotic net is connected to the skin by small additional branches that represent what is described as retinacula cutis. – Apart from giving shape to the breast, these fibrotic structures, support the vascular and ductal components of the gland. The incomplete partition that they provide does not warrant containment of an affliction to a lobular structure. Moreover, along their planes, the fibrotic structures may lead an invasive or an interstitial pathologic process to the skin or to the posterior layer of the fascia and from there, to the pectoralis muscle. – By their convergence toward the nipple, the fibrotic planes determine the flow of breast structures to be directed toward the nipple. Any modification of this normally convergent symmetric flow should be carefully evaluated. Distorted architecture should be regarded with suspicion but it has to be reminded that there are benign processes that may cause architectural distortion. § SUPERIMPOSITION of normal structures, probably the commonest cause for distortion in the daily practice, is usually easy to dismiss. It might be due to insufficient compression of the breast and therefore it is accompanied by additional signs of insufficient compression, like lack of penetration, dropping breast, and asymmetry in one projection. The finding is usually seen in only one projection and to further investigates the distorted region, a retake of the same projection or a spot compression magnification picture of the suspected area might be employed. RADIAL SCAR, (figure 5) an uncommon entity also named, indurative mastopathy, sclerosing duct hyperplasia, or elastosis, has some specific traits that may sometimes indicate the benign nature of the lesion. It is an idiopathic lesion representing a scarring process characterized by lobules trapped in elastic tissue with ducts containing epithelial hyperplasia radiating from the center. It may have the appearance of a spiculated mass but usually the central opacity is missing and the fine, radiating, long lines are interspersed with trapped fat, forming lucent zones near and within the center of the area. A varying appearance in different projections and the absence of a palpable lesion despite a rather large mammographic diameter have also been suggested as typical for this lesion. Albeit characteristic radiologic signs for radial scar seem to exist, they are not sufficiently specific as to deny further investigation. A radiolucent center and elongated radiating spicules were not observed in all radial scar cases and moreover, they were also observed in a minority of matched cancer cases. In most cases the radiolucent center is related at pathologic examination to a fibroelastotic center with entrapped and distorted tubular structures that show a pseudoinfiltrative appearance. Radiating ducts and lobules with varying amounts of ectasia, hyperplasia, and adenosis surrounds the fibroelastoid core. A varying appearance in different projections was infrequently observed and was not typical of radial scar, being seen as frequently in matched cancer cases. The absence of a palpable mass, despite the relatively large diameter of the lesion at mammography, was also frequently observed for radial scar but the reliability of this operator depending sign, is insufficient to deny the need for further investigations. Microcalcifications might be associated to radial scar but their morphology is not specific enough warrant a benign diagnosis. Findings at cytologic examination after fine-needle aspiration did not help clarify the differential diagnosis between radial scar and cancer. No specific cytologic appearance was observed for radial scar and usually even histologic analysis of core biopsy specimens might be unspecific. It can be concluded that although some specific mammographic features may suggest the presence of radial scar, the final differential diagnosis from scirrhous cancer should be based on histologic evidence. At least vacuum assisted biopsy or even surgical biopsy should be advised for all mammographically detected stellate lesions lacking a central mass or having a radiolucent center and thought to represent radial scars. FOCAL BREAST FIBROSIS, (figure 6) an entity mostly discovered in the recent years, by stereotactic breast biopsy, may present itself mostly as a mass but some of the cases, may show as architectural distortion associated to the mass or even as a unique finding. The entity has an uncertain ultrasonographic aspect, showing as hypoechoic, isoechoic or hyperechoic with a peripheral hypoechoic, well-defined or lobulated rim. DISTORTED PARENCHYMAL EDGE a variant of architectural distortion may manifest itself as an actual pulling in, thickening, flattening or straightening of the breast tissue edge, as compared with the corresponding mirror-image tissue of the opposite side (figure 6a). Cancer, benign masses, fibrotic changes or post-surgical scar may all be responsible for this kind of architectural distortion, either on the outer side of the breast tissue, under the subcutaneous fat, or on the inner side of the breast tissue cone, in front of the retromammary fat. The lesion itself, if real, may not be visible due to increased density of the breast tissue, the only sign that might disclose its presence being the desmoplastic reaction, causing distortion of the parenchymal edge. BREAST CANCER (figure 7) that develops in a background of dense breast tissue may be obscured and only the already mentioned desmoplastic reaction distorting the surrounding tissue, may disclose its presence. The same stands true, for early breast cancers that may sometimes manifest themselves as architectural distortion only in the very early stages. The radially oriented filamentous structures represent fibrosis interspersed with tumor extending into the tissue surrounding the cancer. POSTSURGICAL SCARRING (figure 8) made by architectural distortion and increased density may persist for many months following surgery. A local hematoma or seroma, if present following surgery for a benign lesion, may appear as a spiculated mass. In time, they will be eventually reabsorbed, and the breast will heal without any obvious remainder. Postsurgical scar following a benign biopsy is a planar phenomenon when not accompanied by edema or fluid collections and is frequently worrisome in appearance in only one projection. It may not even be evident in an orthogonal view, in contrast to cancer that is usually evident and worrisome in both projections. The scar following a benign biopsy may persist for 6 month to a year and is expected to decrease in size and density on consecutive follow-up studies, eventually disappearing within 1-2 years. On the other hand, a postsurgical scar following a biopsy with malignant results, and added irradiation therapy can persist for 2 to 5 years or longer, due to the delayed healing and added fibrosis caused by the radiation. Such a scar is a tridimensional worrisome finding that should stabilize or improve with time, leaving little evidence of the previous biopsy, but in some women fat necrosis may lead to calcium deposition or a persistent scar. A spiculated area or architectural distortion seen on a mammogram that is done a year or more after surgery, should be carefully correlated with the previous surgical site and with previous mammograms, to asses the changes. Any increase in size, density or local distortion should be regarded with a high degree of suspicion and eventually histologically sampled. BIOPSY OF ARCHITECTURAL DISTORTION is a difficult issue when the lesion does not have a definite central point. Stereotactic localization of a distorted lesion might be hampered by the absence of a focal finding, as the lesion might show different images on the two oblique projections. The precise depth localization (Z-axis) might prove difficult when trying to perform a stereotactic core biopsy or a vacuum assisted biopsy. To get to the correct depth, the very same spot within the lesion has to be marked on both scout pictures. With microcalcifications is usually easy to identify the same grain on both projections, with masses, the approximate center might be found on both pictures but when it comes to architectural distortion, it might be difficult to find the same intersection of fibrotic strands on both pictures. Moreover, a very small cancer may sometimes generate a substantial desmoplastic reaction, making it hard to be certain that the actual lesion has been sampled. § As a provisional conclusion, might be said that if an architecturally distorted lesion is biopsied and the result is benign, skepticism should prevail. The only way to avoid open, surgical biopsy might prove to be vacuum assisted biopsy and very short follow-up at 4-6 month for at least 2 years. Personal and familial anamnesis should be carefully considered. Surgical biopsy and specimen radiography showing the lesion, should be the only way to treat architectural distortion, in cases where doubts about the possibility to precisely localize and remove representative samples will arise.
