CALCIFICATIONS OF BREAST are the smallest structures identified on a mammogram and are always a sign of a past or ongoing breast tissue alteration.
Extremely common, seen in up to 86% of the mammograms, they are usually benign and their frequency increases with age. They may be located anywhere in the breast structures, including skin and interstitial stroma.
Active cell secretion, cellular necrotic debris, inflammation, foreign body reaction, trauma and radiation are the most usual reasons for their formation. Their exact composition remains uncertain. Apatite, calcite, calcium oxalate, oxalic acid, aragonite and traces of aluminium, iron, magnesium, silicon, copper, gold, silver, titanium and some other elements have been identified. Some studies attempted to connect certain compositions or individual elements within calcifications to malignant or benign changes, in order to allow in vivo spectroscopy differentiate malignant from benign breast changes.
Microcalcifications are best-visualized using high-resolution imaging techniques, vigorous compression and radiographic magnification. <> In order to standardize mammographic reporting, reduce confusing breast imaging interpretations and facilitate outcome monitoring, the American College of Radiology implemented the Breast Imaging Reporting and Database System, known as BIRADS (http://www.breastbiopsy.com/birads.html). While dealing with breast calcifications, BIRADS takes into account distribution of the calcifications within a breast and patterns of calcifications, dealing less with basic morphological characteristics of calcifications.
While attempting to analyse breast calcifications, their characteristics have to be taken into account, combinations of these characteristics leading finally to a safe management of a given case. <> However, calcifications may be a sign of benign changes they may also disclose a yet nonpalpable malignant process. When attached to an otherwise “benign-looking” finding, they may reveal, through their characteristics, the true malignant nature of the whole process and on the contrary, by their benign attributes, an otherwise “suspicious-looking” finding may get a less invasive work-up. There are calcifications whose characteristics denote a benign process and other calcifications whose characteristics hint a malignant one. Regardless of the final diagnosis, calcifications should be assessed according to well-established attributes. Shape – Size – Density – Number – Distribution – Location – Associated findings.
SHAPE – The shape of the microcalcifications is probably the most important element in their analysis (fig. 1). They may be punctate, linear, spherical, coarse, cylindrical, smooth, jagged, regular, casting, branching or heterogeneous, with the last three being the most alarming ones.
The erratic growth of a mass and the resulting lack of sufficient blood supply, are the original causes of their emergence. They are in most of the cases, situated within the ductal framework of a cancer and might represent the central primordial structures involved by the neoplastic process. The unpredictable growing process cause the heterogeneity of their shapes by building, dissipating and moulding them, throughout changing the densities and the local pressures of the tissues around them. <> In some cases, the calcifications are secreted within cribriform spaces generated by some cancers, accounting for less characteristic patterns of deposition. As a rule, irregular, comma shaped, angular or branching calcifications, with or without irregular margins are usually due to a malignant process. SIZE – The conditions that favour the appearance of microcalcifications within a malignant process control their size. Being the result of localized randomly distributed and continuous micro-modifications, their size cannot reach large dimensions (fig. 2). Calcifications are often microscopic and seen only by the pathologists but the visible ones may be as small as 0.2 mm. The usual ones, mostly seen on mammograms are not larger than 0.5 mm. but sometimes and especially the casting type may reach sizes up to 1-2 mm. Heterogeneity of their size should be a cause of concern, especially when associated with other suspicion raising elements. DENSITY – Size, shape and chemical composition of the calcifications may influence their radiographic density (fig. 3). Benign processes are usually producing homogeneous, high-density calcifications, while malignancies, by their random evolution, create inhomogeneous, mostly low-density calcifications. NUMBER – A very large number of calcifications may be present within the breast, some having indeterminate characteristics and some clearly benign. The trait we are searching for is aggregation. Aggregation of indeterminate microcalcifications may indicate disease. The rule that five or more microcalcifications within 1 cubic cm. of breast tissue should raise suspicions, may seem arbitrary (fig. 4). Statistically has been proved that less than five microcalcifications grouped together and having benign morphology, have practically no value in indicating a neoplastic process, unless additional suspicious modifications are present. To be suspicious, an isolated cluster of five or more microcalcifications has to be seen within one cubic cm. of breast tissue, on a contact, non-magnified mammogram. There are instances when thousands of microcalcifications may be seen diffusely spread within the breast tissue. The smallest calcifications, forming a cluster or the most densely packed ones are the ones indicating a probably malignant growth. DISTRIBUTION – Calcifications may be distributed in clusters, may fill a segment or may be diffusely scattered over a region, over the entire breast or bilaterally over both breasts (fig. 5, 6). Grouped or clustered calcifications, BIRADS categories 4 or 5 are the most common distribution raising suspicion, although only 25% of them prove to be the result of a malignant process. <> Segmental microcalcifications are distributed within a segmental unit of the breast, including a main duct opening onto the nipple and its branches spreading into the breast. Segmental calcifications may be included in BIRADS categories 2 or 3 if their morphology suggests a past or an ongoing inflammatory process while a suspicious morphology should include them in BIRADS categories 4 or 5. <> Microcalcifications may be the only sign of an intraductal malignant process involving an entire segment, as well as of a multifocal cancer developing as multiple foci of disease within the same ductal unit. Although breast segments are not regular, fixed anatomical structures, contiguous distribution of the calcifications, seen in at least two projections should raise the suspicion of segmental distribution.
Diffusely, scattered calcifications, over a region or the entire breast, have to be at first differentiated from segmental calcifications. True regional and diffusely scattered bilateral microcalcifications are benign, BIRADS categories 2 or 3. <> Linear calcifications are arrayed in a line that may have branching points, but is heading toward the nipple. They may represent an intraductal malignancy spreading through the ductal system and should be included in BIRADS category 4.
It has to be remembered that a focal cluster may be easily overlooked within a breast filled with microcalcifications. When discovered, it has to be separately evaluated starting with spot compression views combined with magnification, until as much information as possible is retrieved and a safe management path is documented.
Multiple groups of microcalcifications spread over the breast are most probably benign, unless there are other characteristics associated with any of the groups that may change the level of suspicion. LOCATION – In order to avoid unnecessary interventions on the breast, the true intramammary location of the calcifications have to be established (fig. 7). Except for cosmetic powders, tattoos and artefacts, dermal calcifications may sometimes have bizarre shapes that may simulate suspicious clusters of microcalcifications. ASSOCIATED FINDINGS – Although calcifications alone are an important sign revealing changes within breast tissue, they may be connected with certain findings that will strengthen or weaken the possibility that they suggest a localized malignant process. Calcifications are usually associated with masses sometimes only with densities or asymmetric breast tissue, all of which may be benign or malignant. They may accompany malignant, benign or post-operative architectural distortion, they may also be associated with dilated ducts or small, invisible cysts. <<>> Analysing breast calcifications may be a laborious process, because all of their characteristics have to be simultaneously taken into account before a conclusion concerning their significance might be reached. <> Morphology alone can in some well-defined instances (popcorn, eggshell or tram-track) point out the benign nature of a breast process. On the other extreme, certain morphologies (branching and casting type) will always be highly suspicious. However, in between there are many morphological possibilities which may not be relied upon to decide whether a certain calcification is the product of a malignant or a benign process. The features of this last category of microcalcifications should be analysed and correlated with the number of elements, their location and distribution within the breast as well as any associated finding, before attempting to include them in a malignant or benign category.
Learning to analyze the individual characteristics of the breast calcifications may be of great help in deciding the real nature of ongoing or past changes within the breast tissue.
The results of this analysis, corroborated with a thorough understanding of other elements or changes within a breast, will usually guide one to a correct decision, allowing a rapid management of a breast finding with a minimum of financial and emotional strain.
