Soft tissue
Adipose tissue tumors
Other benign lesions
Hibernoma
Author: Vijay Shankar, M.D.
Topic Completed: 1 August 2012
Minor changes: 4 January 2022
Copyright: 2002-2022, PathologyOutlines.com, Inc.
PubMed Search: Hibernoma [title]
Table of Contents
Definition / general | Epidemiology | Sites | Clinical features | Radiology images | Case reports | Treatment | Clinical images | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Shankar V. Hibernoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposehibernoma.html. Accessed January 19th, 2022.
Definition / general
- Lipoma containing prominent brown adipocytes that resembles normal brown fat as classic lipoma resembles white fat
Epidemiology
- Rare (2% of lipomas)
- Mean age 26 - 38 years; 60% male
Sites
- Most commonly in axilla, back, mediastinum, shoulder, thigh (Am J Surg Pathol 2001;25:809); also abdominal cavity, arm, breast, paraglottic space, parasacral region, retroperitoneum, spermatic cord
Clinical features
- May produce steroid hormones
Radiology images
Contributed by Mark R. Wick, M.D.
MRI, tricep muscle
Case reports
- 3 month old (Arch Argent Pediatr 2011;109:126)
- 12 year old girl with symptomatic tumor (J Pediatr Hematol Oncol 2008;30:900)
- 25 year old man with mediastinal tumor (J Clin Pathol 2004;57:993)
- 35 year old woman with vulvar tumor (Indian J Pathol Microbiol 2011;54:817)
- 39 year old man with 9 cm thigh mass (Case #245)
- 52 year old woman with mediastinal tumor (Interact Cardiovasc Thorac Surg 2011;12:845)
- 2 hibernomas with p53 overexpression (Arch Pathol Lab Med 2002;126:975)
Treatment
- Excision
- May recur if incompletely excised
Clinical images
Contributed by Mark R. Wick, M.D.
Gluteal cleft
Images hosted on other servers:
Supraclavicular tumor
Gross images
Contributed by Mark R. Wick, M.D.
Images hosted on other servers:
Thigh tumor
Neck tumor
Axilla
Vulva
Microscopic (histologic) description
- Organoid arrangement of uniform large cells resembling brown fat with coarsely granular to multivacuolated cytoplasm that is eosinophilic or pale
- Vacuoles are small and stain for neutral fat
- Nucleus is small, central with no / rare atypia
- Often mixtures of white fat
- May have loose basophilic matrix, features of spindle cell lipoma (if in neck / scalp), only scattered hibernoma cells
- Subtypes: classic, lipoma-like, myxoid (Ann Diagn Pathol 2006;10:104), spindle cell (CD34+)
Microscopic (histologic) images
Contributed by Mark R. Wick, M.D.
Various images
AFIP images
Lobulated pattern
Granular to multivacuolated cytoplasm
Mixed with white fat
Images hosted on other servers:
Granular to multivacuolated cytoplasm
Vascular changes
Neck
Mediastinal
Vulvar
Multivacuolated tumor cells are S100+
Cytology description
- Small, round, brown fat-like cells with uniform, small cytoplasmic vacuoles and regular, small, round nuclei
- Delicate branching capillaries
- Variable mature fat cells (Cancer 2001;93:206)
Positive stains
- S100 (85%), Oil Red O and Sudan Black, CD31 (Arch Pathol Lab Med 2006;130:480)
- Also uncoupling protein 1 / UCP-1
Electron microscopy description
- Resembles brown fat
- Each tumor cell is invested by a basal lamina
- Inverse relationship exists between lipid droplet size and the number of mitochondria per unit of cytoplasm
- Pleomorphic mitochondria with dense matrices or large round mitochondria with transverse lamellar cristae
- Undulating plasmalemmal invaginations, micropinocytotic vesicles, periodic short plasmalemmal densities
- Conspicuous lack of cytoplasmic membrane systems (Hum Pathol 1983;14:677)
Molecular / cytogenetics description
- 11q13-21 rearrangements (also seen in lipomas and liposarcomas)
Differential diagnosis
- Liposarcoma - well differentiated: tumors are deep, have atypia and specific translocations
- Lipoma (classic): lipocytes are not multivacuolated
- Residual brown fat around cervical or axillary lymph nodes: seen in children, not a distinct mass
Additional references
