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The tumor, 5 cm  4 cm  3 cm in size, showed tan to light brown fat separated by fine fibrous trabeculae.
Source publication
Hibernoma is a rare benign tumor that arises from the vestiges of fetal brown fat. We present a case of interscapular hibernoma. Computed tomography scan showed a well-circumscribed, hypodense mass with peripheral enhancement, and magnetic resonance imaging revealed intermediate high T1 and T2 signal intensities with incomplete fat suppression. Alt...
Context in source publication
Context 1
... examination of the tumor showed a tan to light brown color separated by fine fibrous trabeculae ( Fig. 3) with lobulated, well-demarcated margins, and measured about 5 cm  4 cm  3 cm in size. On microscopic examination, this tumor was composed of a mixture of brown and white adipose cells (Fig. 4). The brown adipose cells were charac- terized by granular multivacuolated, eosinophilic, round to oval cells with centrally placed nuclei and ...
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Presenting concerns of the patient:
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Citations
... Hibernomas rarely recur and do not meta size (Gabra et al). 6 This was evident in our case since our patient did not exhibit recurrence or any sign of metastasis on follow up. ...
Hibernomas refer to benign tumours of immature adipose tissue known a brown fat. They are most commonly found in areas where brown adipose tissue is still present in adulthood such as the shoulder, back, neck, best, arm and abdomen. This case study describes a 60 year old male who presented with a growing 15 mm lump in the right forearm. On examination, tenderness in the area surrounding the mass was elicited. A magnetic resonance image of the right forearm was performed which reported a large intramuscular lipomatous tumour within the brachioradialis muscle, in close relation to the neuromuscular bundle. Surgical excision was performed successfully. Histology was consistent with a diagnosis of a hibernoma tumour. The patient healed well with no evidence of infection or recurrence on follow up.
... Microscopically, brown adipocytes consist of several small droplets with many mitochondria containing iron, which provides the typical macroscopical color [16]. Since this makes it more oxygen-dependent, brown adipose tissue is also often endowed with many capillaries [17]. In addition, mammals also have white adipose tissue in which the adipocytes contain only a single lipid droplet [16]. ...
... Removal may be complicated by the hypervascularity and adhesion of the translucent film to a muscle [18]. No malignant transformations have been described in the literature, nor have metastases been re- ported [17]. Table 1 gives an overview of the most important characteristics of a hibernoma. ...
A hibernoma is a rare benign soft tissue tumor which may occur in the whole body. In the head and neck region, it occurs only sporadically and is difficult to distinguish clinically and on imaging from malignant tumors. It typically presents as a slow-growing, mobile, non-sensitive mass. Our case report describes an atypical presentation of a hiber- noma with sudden onset of swelling in the left neck and dysphagia symptoms in a 16-year-old girl. One week later, a superinfection was noted with discharge of pus. A magnetic resonance imaging (MRI) showed a cystic solid mass, but no definitive diagnosis could be made. Therefore, surgical excision of the mass was performed which proved to be a hibernoma on anatomopathological examination. Whole-body MRI did not show similar lesions in other locations to the head and neck region. A hibernoma should be included in the differential diag- nosis in patients presenting with a mass in the head and neck region. It is important to differentiate between benign and malignant tumors since the treatment differs. MRI is the imaging of choice and surgical excision is curative. To our knowledge, this is the first description of a hibernoma with an additional rare abscess formation, making the diagnosis even more difficult.
... Cytogenetics may show structural rearrangements of chromosome 11q13-21, subsequently resulting in deletion of tumor suppressor genes MEN1 and AIP [23]. Treatment of hibernomas is complete surgical excision, with no reports of local or distant recurrence [24]. ...
A 15-month old male presented with several months of abdominal distension. After undergoing thorough workup, he was found to have an intraabdominal mass on imaging. He underwent exploratory laparotomy and resection of a mesenteric mass along with a loop of associated small bowel. On pathology, the mass was consistent with a hibernoma. In retrospect, the mass may have been present on prenatal ultrasound.
Hibernomas a rare, adipocytic tumors of brown fat origin. There have been less than 20 cases of pediatric hibernomas reported in the English literature. Moreover, there have been no previous reports of mesenteric hibernomas in children or those recognized on prenatal imaging. While lipomatous abdominal tumors are exceedingly rare in the neonatal population, this case report highlights that unusual volume of intra-abdominal fat seen on prenatal ultrasound may warrant repeat evaluation in the perinatal period.
... Warwick reported that color Doppler ultrasound is the first choice of imaging modality for the diagnosis of soft tissue tumors because the tumor location and the relationship between blood flow and the adjacent tissues can be dynamically observed in real time [14]. Under color Doppler ultrasound, a hibernoma usually presents as a high-echo mass with a clear boundary accompanied by an increase in blood flow within the tumor [15,16]. Angiography shows increased vascularity within the tumor, which is known as the typical tumor blush, and may even display internal arteriovenous shunting [17]. ...
Background
A hibernoma, also known as a brown fat tumor, is a rare benign soft tissue tumor, which originates from brown adipose tissue remaining in the fetus after the gestational period. It is often detected in adult men, presenting as a painless slow-growing mass. Hibernomas of the thigh have been reported; however, motor and sensory disorders caused by the tumors compressing the femoral nerve have not been reported. We report a case of a histopathologically proven hibernoma that induced femoral mononeuropathy.
Case presentation
A 26-year-old man was admitted to the hospital due to a mass, approximately 11.0 × 9.0 × 4.0 cm in size, that had developed 5 years ago in the anterolateral aspect of the proximal thigh. Furthermore, he had a history of hypoesthesia 1 month prior to his admission. He had signs and symptoms of both a motor and sensory disorder, involving the anterior aspect of the right thigh and the medial aspect of the calf, along the distribution of the femoral nerve. During surgery, the femoral nerve was found to be compressed by the giant tumor. The resultant symptoms probably caused the patient to seek medical care. Marginal resection of the mass was performed by careful dissection, and the branches of the femoral nerve were spared. Histopathology examination showed findings suggestive of a hibernoma. At the 4-month follow-up, no femoral nerve compression was evident, and local tumor recurrence or metastasis was not found.
Conclusions
Asymptomatic hibernomas do not require treatment; however, in cases of hibernomas with apparent symptoms, complete marginal surgical excision at an early stage is a treatment option because it is associated with a low risk of postoperative tumor recurrence.
... For this reason, the PET-CT findings of hibernoma are indistinguishable from malignancy, often leading to a false-positive radiologic interpretation and requiring a biopsy to exclude a malignant etiology [10,14,18]. Infact SUV alone may not accurately reflect the malignant potential of soft tissue tumors but might rather implicate cellular components in the lesions [11,12,16]. ...
Introduction
The present study reports the case of an axillary hibernoma in a patient with lobular homolateral breast cancer and multiple endocrine neoplasia type1 (MEN-1).
Hibernoma is a rare benign adipose tissue tumor, and usually manifests as a slowly growing and painless rubbery mass.
These tumors can arise in various sites, but mammary hibernomas remain extraordinarily uncommon. Although hibernomas are metabolically active and therefore “glucose-avid” on fluorodeoxyglucose CT-positron emission tomography (FDG CT-PET), imaging alone is inadequate in providing a reliable diagnosis and definitive differential diagnosis from other malignancy. Only complete surgical excision is diagnostic and, in most cases, curative.
Presentation of case
A 42-years-old woman was followed for MEN-1 syndrome associating with hyperparathyroidism, insulinoma, non-secretory adrenal adenoma and thyroid lump. A FDG CT-PET found high glucid hypermetabolism in thickened elongated area on the front axillary line.
Hibernoma was diagnosed after realization of prophylactic left mastectomy, homolateral sentinel lymph node biopsy and exeresis of the known axillary lesion.
Discussion
Clinical importance lies in distinguishing hibernoma from other benign and malignant breast neoplasms, as well as inflammatory conditions that come into the histologic or radiologic differential. Hibernoma is not currently classified as a non-endocrine tumor related to MEN1, but this association could be not fortuitous for the linkage between modification of Menin protein function and pathogenesis of hibernomas.
Conclusion
Our case deserves extraordinary attention because, not only it’s a case of MEN1 syndrome associated with hibernoma, but in the context of this lesion there are multiple micro-foci of infiltrating lobular carcinoma.
... About 100 cases have been reported in English scientifi c literature but only 10 cases have described in the head and neck region [2] which is rare especially in the neck region. It accounts for 1.6% of benign lipomatous tumors and about 1.1% of all tumors originating from adipose tissue [3]. We present a rare case of intramuscular hibernoma of the neck region in a 28 years old male. ...
... Hibernoma is a rare fetal adipocytic tumor originating from brown fat resembling which fi rst described as brown fat tumor by Meckel in 1906, termed Hibernoma by Gery in 1914 [2,3]. Hibernoma mostly seen in 3 rd , 4 th and 5 th decades of life, higher prevalence in female [3]. ...
... In our patient, it shows a mass which very well circumscribed and homogenous. Th us reported in latest literature, some characteristics remains diffi cult to distinguish with some malignant and rare tumors such as malignant fi brous histocytoma and angliolipoma [3]. ...
... The brown fat has a thermogenesis function, especially in the first years of a child's life, but it regresses with age [1]. In adults, the most common residual areas of brown fat are usually located in the inter-scapular region, mediastinum, retroperitoneum, back, thigh and, sometimes, in head and neck [2][3][4]. Widely, the remaining of brown fat still remains asymptomatic and has no impact on the homeostasis. In rare cases, the remaining tissue can slowly grow, leading to the occurrence of a soft-tissue tumor. ...
Background
Hibernoma is a rare soft tissue tumor stem from persistent fetal brown fat tissue. This benign tumor may occasionally occur in head and neck area and, in most cases, is characterized by an asymptomatic slow growth.
Case presentation
We presented an uncommon case of hibernoma of the posterior cervical triangle occurring in a 30-year-old man referred to the department of otolaryngology. The patient suffered from a right, very painful, and rapidly growing mass since 3 months. MRI examination reported both an infiltrating mass and a homogenous enhancement of an underlying vascularization after the injection of intravenous contrast. According to the risk of sarcoma, a surgical procedure was made to completely excise the mass that was a hibernoma.
Conclusions
Hibernoma may occur with an uncommon clinical presentation imitating malignancy. MRI plays a key role in the differential diagnosis and surgery remains the better therapeutic approach.
... In a review of 17 cases of hibernomas by Mavrogenis et al. the most common location was found to be thigh, followed by buttock and scapula (3). We came across a few reports in the interscapular region similar to our case (6,7) The tumor size of hibernomas may range from 1 to 24 cm with an average diameter of 9.3 cm. A few rare case reports of massive hibernomas have been reported in abdominal wall and neck (8,9). ...
Hibernomas are extremely rare benign tumors of adipose tissue characterized by an admixture of brown fat cells with granular, multivacuolated cytoplasm and white fat cells. Hibernomas account for 1.6% of benign adipose tissue tumors and approximately 1.1% of all adipocytic tumors. Around 10% of these cases are intramuscular. It was initially described in the early 1900s as being composed of brown fat. Hibernomas usually occur in third to fourth decades of life and the most frequent sites being thigh, trunk, shoulder, back etc. Cytological differential diagnoses of hibernoma include well differentiated liposarcoma, myxoid/round cell liposarcoma, chondroid lipoma and benign granular cell tumor. Due to its abundant vascularity evident on angiography, it can sometimes mimic a malignant lesion, from which it needs to be distinguished as complete surgical excision is the only treatment required for a hibernoma. Moreover, it has no malignant or metastatic potential.
We presented a rare case of intramuscular hibernoma of the scapular region in a 34-year-old male, in which cytology was reported as pleomorphic fibrolipomatous malignant lesion.
... Hibernoma is a benign tumour of brown fat that is also known as fetal lipoma, lipoma of embryonic fat and usually is seen in interscapular, neck, axilla, mediastinal and retro-peritoneal regions of adults where vestiges of brown foetal fat persists beyond foetal life [1,2]. Brown adipocyte characterized by small lipid droplets, high mitochondrial content is seen mostly in newborns and in hibernating mammals and is postulated to play a role in thermoregulation [3]. The high iron content within the mitochondria and the rich blood supply imparts the brown colour to the hibernoma [1,3]. ...
... Brown adipocyte characterized by small lipid droplets, high mitochondrial content is seen mostly in newborns and in hibernating mammals and is postulated to play a role in thermoregulation [3]. The high iron content within the mitochondria and the rich blood supply imparts the brown colour to the hibernoma [1,3]. Microscopically, presence of brown adipocyte cells is common to all the four variants namely typical(lobular pattern with uni-vacuolar and multi-vacuolar adipocytes), myxoid (prominent myxoid change), lipoma like (predominantly and spindle cell type. ...
Introduction:
Hibernomas are uncommon benign proliferations arising from the adipocytes of brown fat usually occurring over back, neck, shoulder, and thighs. It is an underreported entity often misdiagnosed as a lipoma.
Case report:
We report a case of an otherwise healthy thirty-four-year-old male who presented with a painless swelling, with no preceding trauma, involving the right shoulder joint of three months duration. MRI revealed it to be a fatty intense lesion arising within the anterior fibers of the right deltoid. The tumor was removed en-masse with wide local excision through the deltopectoral route. The histopathology of the resected tumor was consistent with the diagnosis of hibernoma. The patient recovered the previously hindered movements at the shoulder joint 2 weeks post-operatively.
Conclusion:
Hibernoma should be considered as a differential diagnosis for soft tissue tumors occurring in the above-mentioned sites. It can be completely resected surgically and no recurrences post-excision have been reported till date.
