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Radiological aspects

The radiological changes induced by the fat transfer in the breast tissue were one of the points criticized at the beginning of this technique. This is a very important point and that is why we have done several studies to describe in a precise and objective way these modifications. Indeed, some feared that radiological changes after fat transfer could disrupt the diagnosis of a possible breast cancer. 

In 1987, following the publication of Bircoll in the Plastic and Reconstructive Surgery Journal, the American Society of Plastic and Reconstructive Surgeons (ASPRS) condamned the transfer of adipose tissue into the breast. This recommendation was made without scientific argument, just on the advice of a committee. However, in the same year and in the same scientific journal, a retrospective study on mammary tissue changes after breast reduction reported that calcifications were found in 50% of cases at 2 years, and the author insisted that, in the majority of the cases, it was possible to distinguish them from those found in cancer. Breast reduction surgery had not sparked any particular debate. It is interesting to note here that the criticism of some sometimes lacks critical sense!

In fact, any breast surgery can lead to radiological changes (which just deserve to be known by radiologists specializing in breast tissue imaging), such as  placing implants, breast reduction, breast reconstruction, breast liposuction, and even radiotherapy or breast biopsies. In order to study the radiological impact of fat transfers in the breasts we have carried out 3 studies: one after lipomodeling of breasts reconstructed by Latissimus Dorsi Flap, the second after lipomodeling of conservative treatment sequelae, and the third after lipomodeling of native breasts.

As a result of these works, the radiological images after lipomodelling are now well known:

  • the formation of microcalcifications is a physiopathological phenomenon still poorly explained. It seems that any breast surgery can lead to their appearance, for example we can find up to 50% micro calcifications at 2 years after a breast reduction. The radiographic descriptive study based on our experience reports about 16% of microcalcifications postoperatively. The character of these microcalcifications after breast surgery or after fat transfer is benign, and perfectly recognizable +++ by the classification of Le Gall. With the current technology of digital radiography, high-performance ultrasound, and even MRI, radiologists are able to differentiate the calcifications resulting from fat necrosis, from that of cancer; and this is done in an easy manner. To summarize, the appearance of microcalcifications does not seem to be crippling to the fat transfer technique provided that the precise semiology of the microcalcifications secondary to a fat transfer is perfectly mastered by the radiologist.
  • The appearance of cytosteatonecrosis areas is possible but if we strictly respect the technique by transferring the fat in multiple three-dimensional stages, and avoiding to excessively saturate the tissues, it is largely avoidable +++. Modern techniques of adipose tissue transfer performed according to the technique we recommend, give very little clinical cytosteatonecrosis. The appearance of areas of extended clinical cytosteatonecrosis is most often linked to a technical defect of the transfer by non-compliance with the principle of the three-dimensional network, or failure to respect the phenomenon of tissue saturation of the recipient site. On the other hand, the precise radiological examination frequently reveals small areas of cytosteatonecrosis in solid form or in the form of oily cysts +++. In the series that we published in the Plastic and Reconstructive Surgery Journal in 2011, we found 25% of typical images of cytosteatonecrosis. The Carvajal series found 20% images of non-calcified oil cysts and 20% calcified oil cysts. The percentage of cytosteatonecrosis zones appearance does not have any significance in itself and corresponds more to the fineness of description of the radiologist who currently can afford to visualize very small lesions.
  • The radiological presentation of the cytosteatonecrosis cyst (“oil cyst”) is variable and progressive over time. Its description takes the following forms:
  • Initially it is a solid nodule on ultrasound, and invisible to mammography.
  • A few months postoperative, the cytosteatonecrosis takes the form of an oily cyst mostly visible in ultrasound, whose diagnosis is obvious. These cysts can be numerous, most often small.
  • Subsequently, over the months, the thin cystic envelope can calcify and thicken.The areas of cytosteatonecrosis then appear as calcifications. These may be round, regular microcalcifications around the cysts, or ACR 2 clear center macrocalcification if the cyst was under 1 cm in size at first.
  • As we can see, the notion of temporal scalability is very important for mammographic analysis. In addition, the appearance of new images, even postoperative of an adipose tissue transfer, can not always be directly attributed to the transfer itself. In fact, like any normal breast, the grafted breast will continue its evolution with the possibility of spontaneous appearance of calcification, or other images.
  • In any case, the radiological description is perfectly codified and it looks never suspicious. Thus, the image of multiple foci of cytosteatonecrosis of small sizes is finally the only specific image of a transfer of adipose tissue, described as the appearance of images in “soap bubbles” ++, small sizes, scattered , of fine outline, calcified. And even if cytosteatonecrosis (such as microcalcifications) can occur after any type of breast surgery: biopsy, conservative treatment, breast reduction, breast reconstruction, liposuction, it is not, as in the transfer of adipose tissue, a cluster described in “soap bubbles”, but an isolated image.

The mass of mammary gland accessible to the mammographic examination, recognized as being difficult to access, especially for a small breast, is increased after the transfer of adipose tissue, and this automatically increases the probability of discovering new images, especially at the level of the mammary base (pre-pectoral region) usually located at the limit of mammographic analysis. As such, this advantage of improving the possibility of discovering a possible suspicious lesion, is also found in the preoperative detection during the assessment of a possible disturbing image, which could then lead the radiologist to continue the analysis to the level of micro-biopsy, and early detection of breast cancer. Overall, the patient is in a situation of reinforced surveillance and safety during the two years of her management (before and after lipomodelling) and, if there is any doubt, the diagnostic certainty must be provided by the histological analysis obtained by microbiopsy or by macrobiopsy +++. It is important to emphasize here that one should not seek an expert opinion: if in doubt, the certainty must be obtained by histology ++++ (micobiopsy or macrobiopsy). It is the radiologist’s experience that will limit the need for it. Hence the interest of working in collaboration with radiologists trained in these radiological aspects (in this spirit we have organized several conferences on “Breast Imaging and Plastic Surgery”).

Breast density is the measure of the proportion of mammary gland relative to fat tissue in a breast. It is well established in the scientific literature that increased breast density decreases the sensitivity and the specificity of mammography screening. In addition, a high breast density is a real risk factor especially for the  so called breast cancer of “interval”. A meta-analysis of 42 studies found a relative risk (RR) of 1.79 for a density of 5 to 24%, of 2.11 for a density of 25 to 49%, of 2.92 for a density of 50 to 74 % and 4.64 for a density greater than 75%. The results of the study conducted in our team on breast density before / after transfer of adipose tissue into the native breast show no statistically significant difference. Nevertheless, the transfer of fat tissue into the native breast sometimes shows the mammographic appearance of less dense areas postoperatively. These low density zones are not homogenous and have no impact on the international ACR classification of breast density. On the other hand, the passage, for example, from a breast of density II at 30%, to a breast of density II at 48%, is not negligible. This is why we attempted to evaluate this change by assessing the density of comparative mammograms in 3 sub-categories, taking into account the variability of the percentage of density within the same ACR category. Thus, a moderate decrease in breast density has been observed quite often, which is favorable for mammographic reading.

An important point of our work is to be underlined. The comparative study did not show any difference in classification of ACR BI-RADS II modified in 2003 by the “Breast Imaging Reporting and Data System” (BI-RADS) of the “American College of Radiology” (ACR), before and after a transfer of adipose tissue. It seems satisfying to observe that there is no worsening of the difficulty of reading the pictures observed, which implicitly says that all elements, even new ones, are read clearly and unambiguously +++. This is a fundamental point of this comparative radiological study, which shows that the ACR classification of mammograms remains stable before and after transfer of adipose tissue into the native breast and does not pose any problems of interpretation to a radiologist trained in this field +++.

In conclusion, following our works, it is possible to conclude that there is no increase in the difficulty of interpreting mammograms after adipose tissue transfer. Although new radiological images do appear after a transfer of adipose tissue in a little less than half of the cases, the analysis of mammograms does not pose a diagnostic problem for a radiologist experienced in breast imaging. The mammary density remains stable, even if we sometimes perceive a localized attenuation of breast density. The management of postoperative radiological monitoring can no longer be considered as a brake on this technique. With the current technology of digital radiology, high-performance ultrasound, and even MRI, radiologists are able to differentiate the calcifications resulting from fat necrosis from those related to cancer and this in an easy manner. The interpretation of mammograms after surgery is precise and unambiguous when the surgeon has followed a strict surgical procedure. However, it seems crucial for the radiologist specializing in breast imaging to have a specific knowledge of the images induced by lipomodeling. A close collaboration between radiologist and plastic surgeon thus constitutes the keystone of the oncologic safety of breast lipomodeling interventions and fat transfers in the breast +++.