Hibernoma - an unusual presentation Article in The Journal of - PDF document

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/275260504 Hibernoma - an unusual presentation Article in The Journal of Clinical and Scientific Research · April 2013 DOI: 10.15380/2277-5706.JCSR.12.074 CITATION READS 1 23 6 authors , including: Rashmi Patnayak Amit Kumar Chowhan Siksha O Anusandhan University Sri Venkateswara Institute of Medical Sciences 176 PUBLICATIONS 368 CITATIONS 59 PUBLICATIONS 261 CITATIONS SEE PROFILE SEE PROFILE Nandyala Rukmangadha Sri Venkateswara Institute of Medical Sciences 51 PUBLICATIONS 190 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: original article 8 View project case report 2 View project All content following this page was uploaded by Rashmi Patnayak on 06 June 2015. The user has requested enhancement of the downloaded file.

Hibernoma - an unusual presentation Amitabh Jena et al Case Report: Hibernoma - an unusual presentation Amitabh Jena, 1 Rashmi Patnayak, 2 Y. Mutheeswaraiah, 3 A.K. Chowhan, 2 N. Rukmangadha, 2 M.Kumaraswamy Reddy 2 Departments of 1 Surgical Oncology, 2 Pathology and 3 General Surgery, Sri Venkateswara Institute of Medical Sciences, Tirupati ABSTRACT Hibernomas are rare benign tumours of brown adipose tissue. They are usually encountered in young males usually in their third decade of life. A 50-year-old lady presented with a swelling over the right forearm region that was soft, non- tender and was gradually increasing in size over the last one year. The patient underwent surgical excision of the mass which was confirmed to be hibernoma (mixed variant). This case is being reported for documenting the occurrence of hibernoma in a rare location (forearm) and in an older women aged 50 years. Key words: Hibernoma, Forearm, Benign tumour Jena A, Patnayak R, Mutheeswaraiah Y, Chowhan AK, Rukmangadha N, Reddy MK, Hibernoma - an unusual presentation. J Clin Sci Res 2013;2:105-7. INTRODUCTION mediastinum, periaortic and perirenal zones are the areas where brown fat generally persists. 3, 4 Hibernomas are rare benign slow-growing, So hibernomas are preferentially seen in these painless neoplasms composed of brown adi- sites. pose tissue admixed with variable proportion of white adipose tissue without any tendency CASE REPORT for recurrence after complete surgical excision. A 50-year-old lady presented with a swelling Hibernoma are mostly documented in case re- over the right forearm that was non-tender, soft, ports and small series. 1-4 In Armed forces Insti- and gradually increasing in size over the last tute of Pathology/ American Registry of Pathol- one year. With the clinical diagnosis of lipoma ogy Press (AFIP) series, hibernoma comprised the mass was excised completely and the ex- 1.6% of benign lipomatous tumours. 5 They are cised specimen was subjected for histopatho- described mainly in young adults, mostly in the logical examination. On gross pathological ex- third decade of life, with slight male predomi- amination, the specimen was irregular with nance. 6 The reported age range is from 2 to 72 nodular external surface measuring 8  7  2 years. 1,4 Compared to lipoma, which is one of cm. Cut-surface was greasy with yellowish ar- the most common soft-tissue tumours originat- eas (Figure 1). Microscopically the lesion was ing from white adipose tissue, hibernoma is well encapsulated and revealed predominantly listed among the rarest of the adipocytic neo- foetal looking adipocytes with vacuolated plasms. 3 Brown adipose tissue is generally cytoplasm with little intervening fibrous ele- present in the foetus and is gradually replaced ment, a few congested capillaries mild by white adipose tissue with advancing age. In lymphomononuclear infiltrate without the pres- the foetus, brown adipose tissue is noted in vari- ence of mitotic figures and necrosis (Figure 2). ous sites such as the interscapular area, poste- Since the present case showed an admixture of rior abdominal wall, suprailiac and pale and eosinophilic stained multivacuolated peripancreatic adipose tissue and near auto- cells, it was diagnosed as hibernoma (mixed nomic ganglia whereas in adults neck, axilla, variant). Received: 15 November, 2012. Corresponding author: Dr Rashmi Patnayak, Assistant Professor, Department of Pathology, Sri Venkateswara Insti- tute of Medical Sciences, Tirupati, India. e-mail: rashmipatnayak2002@yahoo.co.in 105

Hibernoma - an unusual presentation Amitabh Jena et al ity and mitochondria rich eosinophilic granu- lar cytoplasm and is an important source of non- shivering thermogenesis. 4,5 The size of hibernoma is variable ranging from 1 to 24 cm with an average dimension of 9.3 cm. It is usu- ally yellow to brown in color, lobular and well demarcated with soft, greasy cut surface. 1 Histo -pathologically six variants of hibernoma have been described. They are eosinophilic, pale cell, mixed, spindle cell, myxoid and lipoma like. 5 Figure 1: Cut-section of the excised specimen showing The present case was a mixed variant of lobular, greasy yellowish areas hibernoma with both pale and eosinophilic stained cells. Immunohistochemically they stain variably for S-100 protein. 1,4 Increased expression of p53 protein has earlier been re- ported. 8 The aetiology of hibernoma is unknown, al- though many lesions arise at the sites where brown fat is normally found in hibernating ani- mals and human foetuses or newborns. 5 Ac- cording to one theory proposed, in order to ex- plain the origin of hibernoma, the tumour grows Figure 2: Photomicrograph showing foetal looking starting from some islands of brown adipose adipocytes with vacuolated cytoplasm (arrows) admixed tissue that may persist in the white fat tissue; with lymphomononuclear infiltrate (Haematoxylin and on the contrary, tumoural brown fat cells may eosin,  400) develop from white adipose tissue. 4 DISCUSSION In a large published series 1 the most common Merkl first described this unusual tumour in locations for hibernoma included the thigh, 1906; Gery in 1914 termed it as hibernoma be- shoulder, back, neck, chest, arm, and abdomi- cause of its resemblance to the brown adipose nal cavity/retroperitoneum. Though tissue of the hibernating glands of animals hibernomas are described in the upper extrem- which helps in thermoregulation. 7 Apart from ity in literature, the usual site is upper arm several mammalian animals, it may also be whereas our case presented with a forearm present in non-hibernating animals, such as swelling. We found only one such case in lit- mice, rats, monkeys and humans. 4 Clinically, erature. 6 Ultrastructural features of hibernoma hibernomas typically present as progressive, include investment of each tumour cell by basal painless swellings without localized tenderness lamina, an inverse relationship between lipid as was also seen with the present report. 1,3 droplet size and the number of mitochondria Symptoms are usually because of mass effect per unit of cytoplasm, pleomorphic mitochon- resulting from pressure and displacement. 4 In dria with dense matrices or large round mito- our case no such effects were observed. chondria with transverse lamellar cristae, un- dulating plasmalemmal invaginations, Brown adipose tissue is brown-tan in color and micropinocytotic vesicles, periodic short vascular, microscopically comprising of po- plasmalemmal densities, and a conspicuous lygonal, multivacuolated cells with granular cy- lack of cytoplasmic membrane systems. 9 toplasm and ovoid nucleus. The brown colour Though cytogenetic analyses of hibernomas of hibernoma is said to be due to its vascular- 106