Imaging features of soft tissue hibernoma: a review of 73 cases

To review the spectrum of clinical presentations and imaging features of soft tissue hibernoma, emphasizing those which are most characteristic of this diagnosis.

A retrospective review of our institutional pathology and imaging databases from 2004 to 2025 identified 73 soft tissue lesions having a confirmed pathology diagnosis of hibernoma and imaging evaluation. Imaging included MRI (54 cases), CT (29 cases), ultrasound (20 cases), radiography (20 cases), and PET (8 cases).

The 73 soft tissue lesions occurred in 39 males (53.4%) and 34 females (46.6%) from 5 to 75 years of age, with an overall average age and median age of 46 years. Soft tissue lesions measured from 5 to 288 mm in greatest dimension, with a median of 101 mm and a mean of 111.5 mm. Soft-tissue lesions demonstrated characteristic features of T1 shading that was best identified on non-fat-suppressed T1-weighted imaging, which should allow an accurate diagnosis in the majority of soft tissue hibernomatous lesions. The hibernomatous lesions were also delineated on CT, ultrasound, and radiography; however, these modalities did not adequately characterize brown fat to allow a definitive imaging diagnosis. Intestinally, PET imaging, available in 8 patients, demonstrated standardized-uptake-values (SUVmax) averaging 10.4 (range: 3.5-28.1), greater than the conventional PET/CT 2.5 value used as a marker for suggesting malignancy.

Although hibernoma is a relatively uncommon tumor, there are specific imaging features that will allow a confident diagnosis in the majority of cases which arise in soft tissue.