Intraosseous hibernoma: Two case reports and a review of the literature

Abstract

Intraosseous hibernomas are exceedingly rare tumors with only 35 cases reported worldwide. They are composed of vestigial brown adipose tissue and require biopsy and pathologic analysis for definitive diagnosis. Given their propensity to mimic more insidious malignant neoplasms, early and accurate identification may spare the patient both anxiety and invasive therapeutic interventions. In this report, we present two cases of intraosseous hibernomas and provide a review of current literature to further characterize the clinical, radiographic, and histopathologic parameters of these lesions. Clinicians should consider the diagnosis of intraosseous hibernoma when evaluating patients with characteristic presentations as it may be more prevalent than currently reported.

Keywords: Bone tumor; Intraosseous hibernoma; Orthopedic oncology; Pathology; Radiology.

Fig 1

Case 1. Positron emission tomography (PET) demonstrates subtle radiotracer uptake within the right mid-sacrum (arrow).

Fig. 2

Case 1. (A) Axial T1 pelvis MRI demonstrating a T1 hypointense lesion within the right sacrum (arrow). (B) Sagittal fat-saturated T2 weighted image demonstrating the hyperattenuating lesion within the right sacrum (arrow). (C) Axial fat-saturated T1 pre-contrast image demonstrating the T1 hypointense lesion within the right sacrum (arrow). (D) Axial fat-saturated T1 post contrast MRI demonstrating the 2.1 cm enhancing lesion within the right sacrum (arrow).

Fig. 3

Case 1. Axial CT image obtained during CT guided percutaneous biopsy demonstrating mixed sclerotic lesion within the right sacrum (arrow), which was targeted for biopsy.

Fig. 4

Case 2. (A) Coronal oblique T1 pelvis MRI demonstrating a heterogeneous T1 hypointense lesion within the right sacral ala (arrow). (B) Coronal oblique T2 pelvis MRI demonstrating a heterogenous T2 hyperintense lesion within the right sacral ala (arrow). (C) Coronal oblique fat-suppressed T1 post-contrast pelvis MRI demonstrating an enhancing lesion within the right sacral ala (arrow). (D) Coronal oblique T1 pelvis MRI demonstrating a T1 hypointense lesion within the S1 vertebral body (arrow). (E) Coronal oblique T2 pelvis MRI demonstrating a T2 hyperintense lesion within the S1 vertebral body (arrow). (F) Coronal oblique fat-suppressed T1 post-contrast pelvis MRI demonstrating an enhancing lesion within the S1 vertebral body (arrow).

Fig. 5

Axial CT image obtained during percutaneous biopsy demonstrating a sclerotic right sacral ala lesion (arrow), which was targeted for biopsy.

Fig. 6

(A) Cytology specimen smear Papanicolaou stain (40x) demonstrating round to polygonal brown adipocytes with multivacuolated cytoplasm pushing nuclei to the side. (B) Hematoxylin and eosin (20x) microscopy demonstrating clusters of round to polygonal brown adipocytes with multivacuolated cytoplasm pushing nuclei to the side or indenting the nuclei, sitting next to the eosinophilic lamellar bony trabeculae. (C) Hematoxylin and eosin (40x) microscopy demonstrating clusters of round to polygonal brown adipocytes with multivacuolated cytoplasm pushing nuclei to the side or indenting the nuclei, sitting next to the eosinophilic lamellar bony trabeculae. (D) Immunohistochemical stain (40x) shows the lesional brown adipocytes are positive for S100, which also highlights the multivacuolated cytoplasm. Additional slides (not shown) demonstrated cells to be negative for AE1/AE3 and CD68.