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

OBJECTIVE: To review the spectrum of clinical presentations and imaging features of soft tissue hibernoma, emphasizing those which are most characteristic of this diagnosis. MATERIAL AND METHODS: 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). RESULTS: 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. CONCLUSION: 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.