Fat grafting complications: why calcification and cysts form

What complications can occur?

A 2017 review stated that complications of fat grafting are generally few, and named bruising, swelling, pain, infection, necrosis, and calcification ^[1]. Another publication on breast fat grafting stated that if the procedure is not performed properly, fat necrosis, calcification, lumps of fat enclosed in a membrane (cystic lesions), enlarged lymph nodes, distortion of the breast contour, and oversensitivity and itching of the breast or nipple can occur ^[3].

If grafted fat does not receive a blood supply in its new location and fails to survive, it can remain as a firm lump. This is called fat necrosis. When oil released from dead fat cells collects inside a membrane, it becomes an oil cyst, and if calcium builds up over time, it can show up as calcification.

How is fat necrosis defined?

Fat necrosis is a well-known complication after fat grafting and tissue transfer, but a 2014 systematic review found no consistent definition, because the size criteria and timing of assessment varied greatly from study to study ^[4]. The methods used to confirm the diagnosis after examination also varied, ranging from imaging or biopsy to a combination of tests ^[4].

The authors proposed defining fat necrosis as a firm lump under the skin (subcutaneous induration) of 1 cm or larger that can be felt on examination after surgery, has clear borders, and does not go away ^[4]. Fat necrosis can be confirmed through imaging, biopsy, or findings during surgery, and the authors also presented a classification system for grading its severity ^[4].

Rates reported for breast fat grafting

A 2020 systematic review pooled studies of consecutive patients who had breast fat grafting for cosmetic purposes and analyzed 2,073 patients ^[2]. Major complications were rare, at 0.5% for hematoma, 0.6% for infection, and 0.1% for seroma, and no patients needed another operation because of them ^[2]. The most common minor complication was a cyst that could be felt, at 2.0%, and 67% of these were treated by aspiration, in which the contents are drawn out with a syringe ^[2].

On imaging, oil cysts were seen in 6.5%, calcification in 4.5%, and fat necrosis in 1.2% ^[2]. The proportion advised to have additional imaging to rule out malignant (cancerous) changes was 16.4%, and the proportion advised to have a biopsy was 3.2% ^[2]. The authors stated that imaging changes are common but do not appear to lead to findings that require treatment ^[2].

Results of fat grafting after breast cancer surgery

There is also a 2016 systematic review of 2,419 women who had fat grafting for reconstruction after breast cancer treatment ^[5]. Most of the included studies were case series, and for follow-up, mammography was used in 65.2% of the studies, ultrasound in 47.8%, and magnetic resonance imaging (MRI) in 30.4% ^[5].

Reported complications were fat necrosis in 5.31%, benign lesions such as cysts or calcification in 8.78%, and infection in 0.96%, and local recurrence was reported in 1.69% ^[5]. The authors stated that the procedure appears safe from a cancer treatment perspective, but that randomized controlled trials are urgently needed to confirm this ^[5]. Because much of the data had no comparison group, it is difficult to judge the risk from the recurrence figures alone.

Technical principles for reducing complications

Because the results of fat grafting vary and are difficult to predict, many variations have been tried at each stage of harvesting, processing, and injection ^[1]. A 2017 review recommended harvesting with a wide tube and low suction pressure to reduce damage to fat cells, using low-speed centrifugation during processing, and injecting with a thin tube in a fan-shaped pattern, spread over several rounds rather than in a large amount all at once ^[1].

For breast fat grafting as well, the principle has been described that fat should be divided into small amounts and placed in multiple layers, from the chest wall up to the skin ^[3]. It was stated that if the procedure is not performed according to these principles, complications such as the fat necrosis, calcification, and cystic lesions described above can occur ^[3].

If symptoms appear, and what to check during your consultation

In one case report, multiple cysts could be felt 6 months after breast fat grafting, along with asymmetry and pain, and after these were confirmed with ultrasound and MRI, the large lesions were removed surgically ^[3]. If you notice a new lump or pain, it is best not to judge it yourself but to see a doctor. The type and severity of complications vary from person to person.

• The amount of fat injected at one time and how it is divided up
• The plan for regular checkups and imaging after surgery
• The steps for checking a lump if one develops
• Telling the staff about your fat grafting history at breast screenings