Journal of Indian Academy of Oral Medicine and Radiology

CASE REPORT
Year
: 2021  |  Volume : 33  |  Issue : 2  |  Page : 230--232

Hibernoma: A rare benign tumor


R Thriveni1, Sunitha Bhosle1, DN S. V. Ramesh1, AH Praveen2,  
1 Department of Oral Medicine and Radiology, AME's Dental College and Hospital, Raichur, Karnataka, India
2 Department of Oral and Maxillofacial Surgery, AME's Dental College and Hospital, Raichur, Karnataka, India

Correspondence Address:
Dr. Sunitha Bhosle
AME's Dental College and Hospital, Raichur - 584 102, Karnataka
India

Abstract

Hibernomas are rare soft-tissue benign neoplasms composed of brown adipose tissue. In 1906, Merkel named these tumors Pseudolipoma, then in 1914, Grey coined the term as Hibernoma because of its similarity to brown fat in hibernating animal species. Symptoms secondary to extrinsic compression of neighboring structures may be present, although these tumors are uniformly benign. Hibernomas may be found anywhere in normal fetal brown fat but are most commonly located in the thigh. The etiology of Hibernomas is unknown. Molecular genetics show mutation in chromosome 11 which encodes the tumor suppressor gene MEN 1 [Multiple Endocrine Neoplasia type 1]. Among all benign lipomatous tumors approximately 1.6% accounts for Hibernomas.



How to cite this article:
Thriveni R, Bhosle S, S. V. Ramesh D N, Praveen A H. Hibernoma: A rare benign tumor.J Indian Acad Oral Med Radiol 2021;33:230-232


How to cite this URL:
Thriveni R, Bhosle S, S. V. Ramesh D N, Praveen A H. Hibernoma: A rare benign tumor. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Dec 6 ];33:230-232
Available from: https://www.jiaomr.in/text.asp?2021/33/2/230/319077


Full Text



 Introduction



Hibernomas are rare soft-tissue benign neoplasms composed of brown adipose tissue. These tumors are slow growing and mostly asymptomatic unless compression of neighboring structures that may cause secondary symptoms.[1] It commonly occurs in the age group between the third and fifth decades.[2] It mostly occurs in the inter-scapular region, superior mediastinum, axillae, retroperitoneum, and the neck where brown fat existed in the fetus and persisted into adult life.[3] According to a retrospective study of 12 years and analysis of 49 published cases from 1976 to 2017, the mean age was 34.3 years (range 17–71). Histopathological analysis revealed the following subtypes. Simple lipoma 11 (47.8%) followed by fibrolipoma 6 (26%), angiolipoma 2 (8.6%), osteolipoma 1 (4.3%), myxolipoma 1 (4.3%), angiomyxolipoma 1 (4.3%), and hibernoma 1 (4.3%).[4] This article presents a rare case of Hibernoma of lower labial mucosa in a 4-year-old female patient.

 Case Report



A 4-year-old female patient reported along with her parents to the Department of Oral Medicine and Radiology with a chief complaint of growth in the lower front lip region for 3 months, growth was peanut- sized initially and has reached the present size in 3 months. The patient gives no history of pain, but a feeling of discomfort because of the growth. Past dental, family, personal and medical history were non-contributory.

On extraoral examination, there was no significant finding and the submandibular and sublingual group of lymph nodes were not palpable. On intraoral examination, a well-defined solitary growth was seen involving the lower labial mucosa anterior to the angle of the mouth which was roughly round to oval in shape, it was measuring approximately 1.5 cm × 2 cm in size. Growth was inflamed and depressed in the middle aspect with mucosa over the growth appearing yellowish white which is either keratinized or fordyce's tissue. Growth was soft in consistency and movable along with the movement of the lip and the overlying mucosa was not pinchable. The surrounding mucosa was normal [Figure 1].{Figure 1}

 Diagnostic Assessment



Based on the history and intraoral findings like a well-defined solitary growth seen involving the lower labial mucosa which was roughly round to oval in shape the provisional diagnosis was given as traumatic retention cyst.

Differential diagnosis was given as:

[INLINE:1]

 Therapeutic Intervention



Excisional biopsy of the swelling was done under local anesthesia. Microscopic examination showed subepithelial stroma with clusters of polygonal cells with granular cytoplasm and vesicular nucleus confirming it as Hibernoma [Figure 2].{Figure 2}

 Follow Up



The patient was recalled after one week for a follow-up check-up [Figure 3].{Figure 3}

 Timeline of History



[INLINE:2]

 Discussion



Hibernoma is a rare begin soft-tissue tumor of brown fat. In hibernating animals as well as in human neonates and fetuses brown fat serves as a thermoregulator.[1] In species that do not hibernate as in the mammalian the brown adipose tissue regresses with age. The lesions show variability in size, and the classic characteristics of a pink/tan/yellow well-demarcated soft-tissue tumor.[5] Hibernoma contains a high concentration of mitochondria and increased vasculature that gives its dark color and differentiates it from white adipose tissue.[3] In adults, brown fat is largely a vestigial tissue, which is located in the inter-scapular region, superior mediastinum, axillae, retroperitoneum, and the head and neck region.[3] Clinically, hibernomas are very slow growing, painless tumors, either presenting as palpable, soft and mobile mass or as an incidental finding at imaging.[2] However sometimes localised increase in skin temperature may be noted due to hypervascularity.

Hibernoma is remarkably rare in children, only a single pediatric case was reported before 2001 and only 9 of 170 cases occurred before 18 years of age.[6] Furlong et al. reported a total of 170 cases of hibernoma, among these cases the age of presentation was 35 years with male predominance.[7]

Although these tumors are benign without any malignant transformation these tumors size may vary from 3-24 cm.[8] Histologically, hibernoma comprises mainly brown fat cells with granular, multivacuolated cytoplasm in addition to varying amounts of white fat cells, spindled cells, and myxoid stroma. Histologically, four subtype variants are present like typical, lipoma-like, myxoid, and spindle cells.[6]

Hibernoma cannot be diagnosed only using radiographic information; however, radiographic information can help in the surgical treatment of the tumor. Computed tomography with intravenous contrast shows a well-defined mass.[1] Magnetic resonance imaging (MRI) reveals Hibernomas with increased signal in both T1- and T2-weighted images.[9] On T1 weighted imaging, hibernomas are less intense when compared to the subcutaneous tissue. Positron emission tomography (PET) can be used as it can detect hibernomas due to the high metabolic activity of brown adipose tissue.[10]

The pathology of hibernoma has been reported in the literature. Macroscopically, hibernomas may be well defined. Microscopically, the tumor may comprise of large multi-vacuolated cells with abundant mature adipose cells and several small branching capillaries may involve with or without significant adipocytic atypia.[10]

As hibernomas are well-defined and do not show infiltration, thus these tumors can be treated by complete surgical excision.[3] There is no recurrence of the tumor but if incomplete excision is done regrowth of the tumor may be present.[6]

 Conclusion



Hibernomas are soft-tissue benign tumors. According to a 12-year study they occur in the mean age of 34 years and is most commonly seen in the inter-scapular region, the head and neck region. But in our case, a pediatric 4-year-old female patient with a hibernoma on the lower labial mucosa was reported which is the most uncommon and rare site and age of occurrence is also rare. Thus, these tumors should be considered in the differential diagnosis of all lipomatous tumors in both the adult and pediatric populations.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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