Luca Alessandro Carbonaro MD, Presenter: Nothing to Disclose

Nicola Verardi MD, Abstract Co-Author: Nothing to Disclose

Henrida Kule MD, Abstract Co-Author: Nothing to Disclose

Laura Menicagli MD, Abstract Co-Author: Nothing to Disclose

Giovanni Di Leo, Abstract Co-Author: Nothing to Disclose

Francesco Sardanelli MD, Abstract Co-Author: Consultant, Bracco Group

To describe peculiar MRI features of FN of the breast.

We retrospectively evaluated the MRI exams of 15 patients treated with conservative surgery and radiation therapy from 8 months to 15 years before MRI and of one woman under anticoagulant therapy, for a total of 25 lesions diagnosed as FN at a multimodal final assessment (combination of mammography, ultrasonography, and/or histopathology or fine needle aspiration cytology) and at least one-year negative follow-up. All exams were performed at 1.5 T with a 2D axial STIR sequence (TR/TE/TI=5600/70/150 ms; flip angle 180°) and dynamic 3D coronal or axial gradient echo (GE) T1-weighted sequence (TR/TE=11/4.8 ms; flip angle 25°) before/after intravenous injection of 0.1 mmol/kg of Gd-DOTA or Gd-BOPTA (temporal resolution 111-118 s). We compared the signal intensity (SI) in arbitrary units (au) inside the lesion with that of surrounding fat, applying a region of interest on both STIR and unenhanced GE images. All lesions were also evaluated for morphology and dynamics according to BI-RADS descriptors. Wilcoxon test was used.

Out of 25 lesions, 19 (76%) showed ring enhancement (2 with irregular borders and a washout curve). At STIR sequence, the mean lesion diameter was 13±5 mm (mean±standard deviation); lesions were markedly hypointense (median SI=43 au) in comparison with the suppressed surrounding fat (median SI=204 au) (P=.001), appearing as a “black hole” within the breast. Conversely, at the unenhanced GE sequence, lesions showed a dark periphery in all cases, with irregular margins in 8/25 (32%) while a high SI inside the lesion (median SI=374 au) was observed, not significantly different in comparison with that of surrounding fat (median SI=386 au) (P=.776).

FN may mimic MRI appearance of breast cancer due to irregular margins and peripheral enhancement. The combination of internal high SI at GE images and of a “black hole” at STIR images, never observed for other benign lesions or cancers, is typical of FN. This signal behavior can be related to the high magnetic homogeneity due to the rupture and saponification of long-chain fatty acids in the context of necrosis.

Peculiar features of FN make possible a sure MRI diagnosis, avoiding unnecessary invasive procedures for a definitive diagnosis.

Carbonaro, L, Verardi, N, Kule, H, Menicagli, L, Di Leo, G, Sardanelli, F, MRI of Fat Necrosis (FN) of the Breast: The “Black Hole” Sign at Short Time Inversion Recovery (STIR) Sequence.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8015191.html