For women who underwent silicone implant reconstruction after breast cancer treatment, enlarged internal mammary lymph nodes (IMLNs) can be a cause for concern. However, a new study published in the November issue of Radiology has demonstrated that in most cases, IMLNs spotted on MRI are benign.
“IMLNs identified at implant-protocol breast MR imaging after oncoplastic surgery for breast cancer are overwhelmingly more likely to be benign than malignant,” wrote authors Elizabeth Sutton, MD, of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues. “Imaging follow-up instead of immediate metastatic work-up may be warranted.”
The authors noted an increasing rate of mastectomy, which can be followed by reconstruction using synthetic implants. FDA recommendations call for MRI screening of women receiving silicone gel-filled implants to look for ruptures at regular intervals after implantation.
During this screening, enlarged IMLNs could be uncovered, owing to nonspecific inflammation or silicone migration, but Sutton and colleagues explained that differential diagnosis includes breast cancer or second primary nodal metastases.
Since tissue diagnosis of enlarged IMLNs is difficult, the authors conducted a study of 923 breast cancer patients with silicone implants to assess the rate of malignancy.
Patients underwent postoperative implant-protocol MRI with or without PET/CT from 2000 to 2013. The largest IMLNs were measured, and pathologically proven to be benign or malignant. Those that were stable or showing no signs of disease at one year also were classified as benign.
Overall, 37.6 percent of women in the study had IMLNs, with median short- and long-axis measurements of 0.40 cm and 0.70 cm, respectively. Of the 207 IMLNs with significant follow-up, only one was malignant, with a positive predictive value of 0.005.
Fifty eight patients underwent PET/CT, and 12 had FDG-avid IMLNs, but only one of these was malignant.
“IMLNs are commonly seen at breast MR imaging among women who have undergone silicone implant breast reconstruction. The interpreting radiologist should be aware of this finding and understand that the likelihood that it represents recurrent disease is extremely low, even with FDG avidity,” wrote Sutton and colleagues.