Journal of Orthopaedic Surgery 2014;22(1):118-21
Hibernoma of the thigh: a report of four cases Bouabid Salim, Chagar Belkacem
Orthopedic Department, Military Hospital of Rabat, Faculty of Medicine Mohamed V University Rabat, Morocco
CASE REPORTS ABSTRACT Hibernoma is a rare benign adypocyte tumour of brown fat. We report on 4 patients with hibernoma of the thigh. Clinical features and magnetic resonance imaging suggested the tumours were liposarcomas, but biopsy yielded the diagnosis of hibernoma. All 4 patients underwent complete excision of the tumour and had no recurrence. Key words: lipoma; thigh
INTRODUCTION Hibernoma (a type of lipoma) is a rare benign tumour of soft tissue. It develops in areas where brown fat persists and manifests as a slow-growing, painless mass. It is difficult to differentiate it from other types of lipoma and hypervascular lesions such as liposarcoma.
Records of 3 women and one man aged 35 to 54 (mean, 46) years with hibernoma of the thigh treated in our hospital between 1994 and 2006 were reviewed (Table). The tumours were located in the posterior (n=1) and anteromedial (n=3) compartments and had existed for 6 to 14 years. The masses were 12 to 22 cm in diameter, firm, painless, non-pulsatile, movable on the surface but fixed to the muscle. The patients had normal C-reactive protein level and no inflammation. Sensorimotor control and all distal pulses were present. In one patient, the tumour expanded rapidly over 6 months and resulted in discomfort during walking and weight loss. Radiography revealed no calcification. In one patient, computed tomography revealed the mass to be hyperintense and heterogeneous, with a zone of central necrosis and no bone abnormality (Fig. 1). In another patient, the mass was hypointense even after contrast enhancement (Fig. 1). In the other 2 patients, magnetic resonance imaging was isointense on T1weighted images and hyperintense on T2-weighted
Address correspondence and reprint requests to: Bouabid Salim, Orthopedic Department, Military Hospital of Rabat, Mohamed V University of Rabat, Morocco. Email: [email protected]
Vol. 22 No. 1, April 2014
Hibernoma of the thigh 119 Table Four patients with hibernomas of the thigh
Sex/age (years)
F/53 M/40
Location
Time from occurrence to presentation (years)
Anterolateral thigh Anterolateral thigh
10
Slow-growing mass
12 6
Rapid increase within 6 months, intense weight loss Slow-growing mass
14
Slow-growing mass
F/35
Posterior thigh
M/54
Anterolateral thigh
(a)
Symptom
Radiological features
Volume (cm)
Histology
Hyperintense with heterogeneous 6x12x18 Hibernoma enhancement Hyperintense on T1- & T2-weighted 6x12x22 Hibernoma images, contrast-enhanced compared to subcutaneous fat Hyperintense on T1- & T2-weight 9x10x14 Lipoma-like images, contrast-enhanced fatsuppressed on T1-weighted images, vessels are noted Hypointense without enhancement 6x6x15 Lipoma-like after contrast injection
Followup (years) 12 2 1
0.6
(b)
Figure 1 Computed tomography showing the hibernoma to be (a) hyperintense with vessels after contrast enhancement and (b) hypointense without contrast enhancement, with vessels within (arrow).
images, with fat saturation (Fig. 2). After injection of Gadolinium, there was diffuse contrast enhancement corresponding to the vascular branches (Fig. 2). All 4 patients underwent biopsy and the histological diagnosis was hibernoma in 2 and ‘lipoma-like’ in the other 2 (Fig. 3). All patients underwent complete excision under local anaesthesia. In one patient, the tumour was hypervascular. At the last follow-up, no patient had recurrence or functional deficit.
DISCUSSION In hibernating animals, brown fat plays an important role in temperature regulation and energy.1 Hibernoma develops from foetal brown fat. In adults, brown fat is mostly located in the shoulder region and neck. It can be encountered at any age, the peak being the third decade,1–3 and it shows a slight female predominance.4,5 Common sites of hibernoma are the shoulder, back, neck, thorax, arm, and abdomen,6,7
Journal of Orthopaedic Surgery
120 B Salim and C Belkacem
(a)
(b)
Figure 2 Magnetic resonance imaging showing the mass to be hyperintense on (a) a T2-weighted coronal image, and (b) a fat-suppressed, contrast-enhanced, T1-weighted axial image, with vessels within (arrows).
Figure 3 Multivacuolated cells with a central pit and eosinophilic cytoplasm (H&E, x400).
and 30% occur in the thigh.8 Hibernomas usually grow slowly but can also grow rapidly, and sometimes cause pain when they compress adjacent structures.9 Some are warm to touch owing to their vascular nature.8 They may be associated with intense weight loss, owing to excessive thermogenesis via intense catabolism of carbohydrate and lipid in brown fat. Body weight returns to normal after their excision.10 The diagnosis is difficult,4 and rarely by radiography.1,11 Ultrasonography reveals hibernomas
to be uniformly hyperechogenic, whereas angiography shows highly vascularised tumours with occasional arteriovenous shunts. Technetium99 scintigraphy yields areas of increased uptake. Computed tomography shows the tumour density to be intermediate between muscle and fat, with possible heterogeneous enhancement after contrast enhancement, and the presence of intratumoral vessels.12,13 In addition, the tumour can be hypointense4,14 or slightly hyperintense,11 compared to the subcutaneous fat. Magnetic resonance imaging enables making a specific diagnosis, using the signal characteristics of soft tissues.15 The masses can be hypointense or isointense on T1-weighted images or isointense or hypointense on T2-weighted images (relative to the fat).11,15 Fatty-suppressed sequences can reveal its vessels.1,16 The Gadolinium enhancement is particularly intense in areas of low signal.16 Signals vary depending on the cellular composition of each hibernoma.17 The differential diagnosis includes lipoma, angiolipoma, malignant fibrous histiocytoma, and liposarcoma.1 Thus, biopsy is necessary to confirm the diagnosis. Percutaneous biopsy confers a haemorrhage risk due to their vascularity.16,18,19 The tumours are encapsulated by a fine translucent film and may adhere to fine trabecular muscle, making them difficult to excise. These adhesions should not be interpreted as features of malignancy.20 The hibernomas are characterised by various levels of differentiation and a mixture of mature
Vol. 22 No. 1, April 2014
adipocytes cells, multivacuolar cells, and round cells, with a central pit and eosinophilic cytoplasm corresponding to the brown fat cells. Hibernomas can be classified into 4 histological variants: typical, spindle, lipoma-like, and myxoid. Cytogenetically, hibernomas are characterised by chromosomal aberrations with a reciprocal translocation involving 9q34 and 11q13 bands t (9;11) (q34; q13).21
Hibernoma of the thigh 121
As hibernomas are very vascular, maintaining haemostasis during surgical excision is important, and they do not degenerate.22 DISCLOSURE No conflicts of interest were declared by the authors.
REFERENCES 1. Atilla S, Eilenberg SS, Brown JJ. Hibernoma: MRI appearance of a rare tumor. Magn Reson Imaging 1995;13:335–7. 2. DeRosa DC, Lim RB, Lin-Hurtubise K, Johnson EA. Symptomatic hibernoma: a rare soft tissue tumor. Hawaii J Med Public Health 2012;71:342–5. 3. Paul MA, Koomen AR, Blok P. Hibernoma, a brown fat tumour. Neth J Surg 1989;41:85–7. 4. Della Volpe C, Salazard B, Casanova D, Vacheret H, Bartoli JF, Magalon G. Hibernoma of the antero-lateral thigh. Br J Plast Surg 2005;58:859–61. 5. Lewandowski PJ, Weiner SD. Hibernoma of the medial thigh. Case report and literature review. Clin Orthop Relat Res 1996;330:198–201. 6. Ahn C, Harvey JC. Mediastinal hibernoma, a rare tumor. Ann Thorac Surg 1990;50:828–30. 7. Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. London: Mosby; 1995:420–3. 8. Lee JC, Gupta A, Saifuddin A, Flanagan A, Skinner JA, Briggs TW, et al. Hibernoma: MRI features in eight consecutive cases. Clin Radiol 2006;61:1029–34. 9. Furlong MA, Fanburg-Smith JC, Miettinen M. The morphologic spectrum of hibernoma: a clinicopathologic study of 170 cases. Am J Surg Pathol 2001;25:809–14. 10. Essadel A, Bensaid Alaoui S, Mssrouri R, Mohammadine E, Benamr S, Taghy A, et al. Hibernoma: a rare case of massive weight loss [in French]. Ann Chir 2002;127:215–7. 11. Dursun M, Agayev A, Bakir B, Ozger H, Eralp L, Sirvanci M, et al. CT and MR characteristics of hibernoma: six cases. Clin Imaging 2008;32:42–7. 12. Anderson SE, Schwab C, Stauffer E, Banic A, Steinbach LS. Hibernoma: imaging characteristics of a rare benign soft tissue tumor. Skeletal Radiol 2001;30:590–5. 13. Murphey MD, Carroll JF, Flemming DJ, Pope TL, Gannon FH, Kransdorf MJ. From the archives of the AFIP: benign musculoskelatal lipomatous lesions. Radiographics 2004;24:1433–66. 14. Balestreri L, Canzonieri V. Case report: Axillary hibernoma—radiological and pathological findings of a rare tumour. Clin Radiol 1998;53:853–5. 15. Datir A, James SL, Ali K, Lee J, Ahmad M, Saifuddin A. MRI of soft-tissue masses: the relationship between lesion size, depth, and diagnosis. Clin Radiol 2008;63:373–80. 16. Fnini S, Arssi M, Hassoun J, Garche A, Largab A. Hibernome of the thigh [in French]. Ann Chir Plast Esthet 2011;56:160–2. 17. Baldi A, Santini M, Mellone P, Esposito V, Groeger AM, Caputi M, et al. Mediastinal hibernoma: a case report. J Clin Pathol 2004;57:993–4. 18. Alahyane A, Bounaim A, Jahid A, Janati IM. Hibernoma of the forearm [in French]. Chir Main 2006;25:166–8. 19. Bilterys L, Versailles L, Ragragui M, Schoofs M. A case of hibernoma of the thigh [in French]. Ann Chir Plast Esthet 1986;31:261–2. 20. Nigrisoli M, Ruggieri P, Picci P, Pignatti G. Case report 489: hibernoma of left thigh. Skeletal Radiol 1988;17:432–5. 21. Turaga KK, Silva-Lopez E, Sanger WG, Nelson M, Hunter WJ, Miettinen M, et al. A (9;11)(q34;q13) translocation in a hibernoma. Cancer Genet Cytogenet 2006;170:163–6. 22. Boudana D, Wolber A, De Lesalle EM, Delaporte E, Martinot-Duquennoy V. Hibernoma: an uncommon adipocytic tumor [in French]. Ann Chir Plast Esthet 2011;56:156–9.
Hibernoma of the thigh: a report of four cases Bouabid Salim, Chagar Belkacem
Orthopedic Department, Military Hospital of Rabat, Faculty of Medicine Mohamed V University Rabat, Morocco
CASE REPORTS ABSTRACT Hibernoma is a rare benign adypocyte tumour of brown fat. We report on 4 patients with hibernoma of the thigh. Clinical features and magnetic resonance imaging suggested the tumours were liposarcomas, but biopsy yielded the diagnosis of hibernoma. All 4 patients underwent complete excision of the tumour and had no recurrence. Key words: lipoma; thigh
INTRODUCTION Hibernoma (a type of lipoma) is a rare benign tumour of soft tissue. It develops in areas where brown fat persists and manifests as a slow-growing, painless mass. It is difficult to differentiate it from other types of lipoma and hypervascular lesions such as liposarcoma.
Records of 3 women and one man aged 35 to 54 (mean, 46) years with hibernoma of the thigh treated in our hospital between 1994 and 2006 were reviewed (Table). The tumours were located in the posterior (n=1) and anteromedial (n=3) compartments and had existed for 6 to 14 years. The masses were 12 to 22 cm in diameter, firm, painless, non-pulsatile, movable on the surface but fixed to the muscle. The patients had normal C-reactive protein level and no inflammation. Sensorimotor control and all distal pulses were present. In one patient, the tumour expanded rapidly over 6 months and resulted in discomfort during walking and weight loss. Radiography revealed no calcification. In one patient, computed tomography revealed the mass to be hyperintense and heterogeneous, with a zone of central necrosis and no bone abnormality (Fig. 1). In another patient, the mass was hypointense even after contrast enhancement (Fig. 1). In the other 2 patients, magnetic resonance imaging was isointense on T1weighted images and hyperintense on T2-weighted
Address correspondence and reprint requests to: Bouabid Salim, Orthopedic Department, Military Hospital of Rabat, Mohamed V University of Rabat, Morocco. Email: [email protected]
Vol. 22 No. 1, April 2014
Hibernoma of the thigh 119 Table Four patients with hibernomas of the thigh
Sex/age (years)
F/53 M/40
Location
Time from occurrence to presentation (years)
Anterolateral thigh Anterolateral thigh
10
Slow-growing mass
12 6
Rapid increase within 6 months, intense weight loss Slow-growing mass
14
Slow-growing mass
F/35
Posterior thigh
M/54
Anterolateral thigh
(a)
Symptom
Radiological features
Volume (cm)
Histology
Hyperintense with heterogeneous 6x12x18 Hibernoma enhancement Hyperintense on T1- & T2-weighted 6x12x22 Hibernoma images, contrast-enhanced compared to subcutaneous fat Hyperintense on T1- & T2-weight 9x10x14 Lipoma-like images, contrast-enhanced fatsuppressed on T1-weighted images, vessels are noted Hypointense without enhancement 6x6x15 Lipoma-like after contrast injection
Followup (years) 12 2 1
0.6
(b)
Figure 1 Computed tomography showing the hibernoma to be (a) hyperintense with vessels after contrast enhancement and (b) hypointense without contrast enhancement, with vessels within (arrow).
images, with fat saturation (Fig. 2). After injection of Gadolinium, there was diffuse contrast enhancement corresponding to the vascular branches (Fig. 2). All 4 patients underwent biopsy and the histological diagnosis was hibernoma in 2 and ‘lipoma-like’ in the other 2 (Fig. 3). All patients underwent complete excision under local anaesthesia. In one patient, the tumour was hypervascular. At the last follow-up, no patient had recurrence or functional deficit.
DISCUSSION In hibernating animals, brown fat plays an important role in temperature regulation and energy.1 Hibernoma develops from foetal brown fat. In adults, brown fat is mostly located in the shoulder region and neck. It can be encountered at any age, the peak being the third decade,1–3 and it shows a slight female predominance.4,5 Common sites of hibernoma are the shoulder, back, neck, thorax, arm, and abdomen,6,7
Journal of Orthopaedic Surgery
120 B Salim and C Belkacem
(a)
(b)
Figure 2 Magnetic resonance imaging showing the mass to be hyperintense on (a) a T2-weighted coronal image, and (b) a fat-suppressed, contrast-enhanced, T1-weighted axial image, with vessels within (arrows).
Figure 3 Multivacuolated cells with a central pit and eosinophilic cytoplasm (H&E, x400).
and 30% occur in the thigh.8 Hibernomas usually grow slowly but can also grow rapidly, and sometimes cause pain when they compress adjacent structures.9 Some are warm to touch owing to their vascular nature.8 They may be associated with intense weight loss, owing to excessive thermogenesis via intense catabolism of carbohydrate and lipid in brown fat. Body weight returns to normal after their excision.10 The diagnosis is difficult,4 and rarely by radiography.1,11 Ultrasonography reveals hibernomas
to be uniformly hyperechogenic, whereas angiography shows highly vascularised tumours with occasional arteriovenous shunts. Technetium99 scintigraphy yields areas of increased uptake. Computed tomography shows the tumour density to be intermediate between muscle and fat, with possible heterogeneous enhancement after contrast enhancement, and the presence of intratumoral vessels.12,13 In addition, the tumour can be hypointense4,14 or slightly hyperintense,11 compared to the subcutaneous fat. Magnetic resonance imaging enables making a specific diagnosis, using the signal characteristics of soft tissues.15 The masses can be hypointense or isointense on T1-weighted images or isointense or hypointense on T2-weighted images (relative to the fat).11,15 Fatty-suppressed sequences can reveal its vessels.1,16 The Gadolinium enhancement is particularly intense in areas of low signal.16 Signals vary depending on the cellular composition of each hibernoma.17 The differential diagnosis includes lipoma, angiolipoma, malignant fibrous histiocytoma, and liposarcoma.1 Thus, biopsy is necessary to confirm the diagnosis. Percutaneous biopsy confers a haemorrhage risk due to their vascularity.16,18,19 The tumours are encapsulated by a fine translucent film and may adhere to fine trabecular muscle, making them difficult to excise. These adhesions should not be interpreted as features of malignancy.20 The hibernomas are characterised by various levels of differentiation and a mixture of mature
Vol. 22 No. 1, April 2014
adipocytes cells, multivacuolar cells, and round cells, with a central pit and eosinophilic cytoplasm corresponding to the brown fat cells. Hibernomas can be classified into 4 histological variants: typical, spindle, lipoma-like, and myxoid. Cytogenetically, hibernomas are characterised by chromosomal aberrations with a reciprocal translocation involving 9q34 and 11q13 bands t (9;11) (q34; q13).21
Hibernoma of the thigh 121
As hibernomas are very vascular, maintaining haemostasis during surgical excision is important, and they do not degenerate.22 DISCLOSURE No conflicts of interest were declared by the authors.
REFERENCES 1. Atilla S, Eilenberg SS, Brown JJ. Hibernoma: MRI appearance of a rare tumor. Magn Reson Imaging 1995;13:335–7. 2. DeRosa DC, Lim RB, Lin-Hurtubise K, Johnson EA. Symptomatic hibernoma: a rare soft tissue tumor. Hawaii J Med Public Health 2012;71:342–5. 3. Paul MA, Koomen AR, Blok P. Hibernoma, a brown fat tumour. Neth J Surg 1989;41:85–7. 4. Della Volpe C, Salazard B, Casanova D, Vacheret H, Bartoli JF, Magalon G. Hibernoma of the antero-lateral thigh. Br J Plast Surg 2005;58:859–61. 5. Lewandowski PJ, Weiner SD. Hibernoma of the medial thigh. Case report and literature review. Clin Orthop Relat Res 1996;330:198–201. 6. Ahn C, Harvey JC. Mediastinal hibernoma, a rare tumor. Ann Thorac Surg 1990;50:828–30. 7. Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. London: Mosby; 1995:420–3. 8. Lee JC, Gupta A, Saifuddin A, Flanagan A, Skinner JA, Briggs TW, et al. Hibernoma: MRI features in eight consecutive cases. Clin Radiol 2006;61:1029–34. 9. Furlong MA, Fanburg-Smith JC, Miettinen M. The morphologic spectrum of hibernoma: a clinicopathologic study of 170 cases. Am J Surg Pathol 2001;25:809–14. 10. Essadel A, Bensaid Alaoui S, Mssrouri R, Mohammadine E, Benamr S, Taghy A, et al. Hibernoma: a rare case of massive weight loss [in French]. Ann Chir 2002;127:215–7. 11. Dursun M, Agayev A, Bakir B, Ozger H, Eralp L, Sirvanci M, et al. CT and MR characteristics of hibernoma: six cases. Clin Imaging 2008;32:42–7. 12. Anderson SE, Schwab C, Stauffer E, Banic A, Steinbach LS. Hibernoma: imaging characteristics of a rare benign soft tissue tumor. Skeletal Radiol 2001;30:590–5. 13. Murphey MD, Carroll JF, Flemming DJ, Pope TL, Gannon FH, Kransdorf MJ. From the archives of the AFIP: benign musculoskelatal lipomatous lesions. Radiographics 2004;24:1433–66. 14. Balestreri L, Canzonieri V. Case report: Axillary hibernoma—radiological and pathological findings of a rare tumour. Clin Radiol 1998;53:853–5. 15. Datir A, James SL, Ali K, Lee J, Ahmad M, Saifuddin A. MRI of soft-tissue masses: the relationship between lesion size, depth, and diagnosis. Clin Radiol 2008;63:373–80. 16. Fnini S, Arssi M, Hassoun J, Garche A, Largab A. Hibernome of the thigh [in French]. Ann Chir Plast Esthet 2011;56:160–2. 17. Baldi A, Santini M, Mellone P, Esposito V, Groeger AM, Caputi M, et al. Mediastinal hibernoma: a case report. J Clin Pathol 2004;57:993–4. 18. Alahyane A, Bounaim A, Jahid A, Janati IM. Hibernoma of the forearm [in French]. Chir Main 2006;25:166–8. 19. Bilterys L, Versailles L, Ragragui M, Schoofs M. A case of hibernoma of the thigh [in French]. Ann Chir Plast Esthet 1986;31:261–2. 20. Nigrisoli M, Ruggieri P, Picci P, Pignatti G. Case report 489: hibernoma of left thigh. Skeletal Radiol 1988;17:432–5. 21. Turaga KK, Silva-Lopez E, Sanger WG, Nelson M, Hunter WJ, Miettinen M, et al. A (9;11)(q34;q13) translocation in a hibernoma. Cancer Genet Cytogenet 2006;170:163–6. 22. Boudana D, Wolber A, De Lesalle EM, Delaporte E, Martinot-Duquennoy V. Hibernoma: an uncommon adipocytic tumor [in French]. Ann Chir Plast Esthet 2011;56:156–9.
