Hibernomas are usually located in the interscapular region, but may also be encountered in the cervical, thigh or axillary areas. Intra thoracic, intramuscular, abdominal and retroperitoneal lesions have also been described, as well as exceptional locations such as the uterus, breast, popliteal area, cranium, pericardium [1] or mediastinum. Lesions may be multiple or bilateral, are painless, but may cause symptoms related to their mass effect [2] or to their secretory activity, as they are known to sometimes produce steroid hormones. They are usually described as slow growing (but fast growth is also possible) and firm or rubbery and are mostly encountered in adults in their thirties, and differential diagnosis with lipomas and liposarcomas must be taken into consideration, given that clinical presentations of the three pathological entities often overlap [3] [4]. Once the diagnosis of hibernoma is established, the physician does not need to be concerned about malignant transformation or metastasis [5]. However, recurrence is possible, although very rare.

The first step in diagnosing a hibernoma after the clinical suspicion is raised is to perform imaging procedures. A radiography of the affected region will show no bone erosion or calcification. Echography describes hyperechoic tissue, while Doppler imaging highlights the presence of enlarged vessels. Computer tomography scanning describes well vascularized, well circumscribed, heterogeneous, diffusely septated lesions with a possibly incomplete peripheral capsule. Hibernoma signal intensity in magnetic resonance imaging is variable [6], usually high, but slightly inferior to that of subcutaneous tissue [5]. The degree of homogeneity is variable [7]. This method shows diffuse gadolinium enhancement of an otherwise isointense or mildly hypointense tissue formation. Myxoid hibernomas, being richer in water have higher signal intensity on magnetic resonance imaging scans [8]. Fluorodeoxyglucose positron emission tomography shows important radiotracer capture [9] due to the fact that hibernomas contain numerous mitochondria and are metabolically very active. Scintigraphy also reveals high radiotracer uptake with 99mTc-tetrofosmin, 123I-meta-iodobenzylguanidine and 99mTc-methoxyisobutylisonitrile administration. If an angiography is considered to be necessary, it may reveal, besides intense vascularization, the presence of internal arterio-venous shunting [10] which is important information prior to excision.

If clinical and imaging differential diagnosis cannot exclude a malignancy, excision is imperative. Analysis of the surgical specimen reveals a light brown to gray mass of tissue surrounded by a thin capsule [11]. Microscopic examination reveals high -number of mature, multivacuolated or uni vacuolar adipocytes intersecting with brown fat, intense vascularization, and few adipocyte atypia. Tumors may, however, be more or less well differentiated. Immunohistochemical analysis shows a positive cluster of differentiation (CD) 68 and negative CD 34.

In cases where cytogenic analysis reveals the presence of a 11q13 translocation, liposarcoma is improbable [12]. Rearrangements in the 11q13-21 region can be detected using metaphase fluorescent in situ hybridization.

The primary treatment for hibernoma is surgical removal. Since hibernomas are benign, complete excision usually results in a cure. Surgery is generally straightforward, and the prognosis after removal is excellent. In rare cases where the tumor is located in a challenging area, or if the patient has other health concerns, the surgical approach may be adjusted accordingly.

The prognosis for patients with hibernoma is very favorable. Once the tumor is surgically removed, recurrence is rare. Hibernomas do not metastasize (spread to other parts of the body), and patients typically recover fully after surgery. Long-term follow-up is usually not necessary unless there are specific concerns.

The exact cause of hibernoma is not well understood. It is believed to arise from remnants of brown fat tissue that persist into adulthood. There is no known genetic or environmental factor that predisposes individuals to develop hibernomas. They occur sporadically and are not associated with any particular lifestyle or health condition.

Hibernomas are rare, with only a few hundred cases reported in the medical literature. They can occur at any age but are most commonly diagnosed in adults between the ages of 20 and 50. There is no significant gender predilection, meaning they occur equally in males and females. Due to their rarity, hibernomas are often underdiagnosed or misdiagnosed as other types of soft tissue tumors.

Hibernomas originate from brown adipose tissue, which is responsible for thermogenesis (heat production) in the body. Brown fat is more prevalent in infants and decreases with age, but remnants can persist in adults. The tumor is composed of cells that resemble brown fat cells, with abundant mitochondria and a rich blood supply, which contribute to its characteristic appearance on imaging studies.

There are no known measures to prevent hibernoma, as its development is not linked to any modifiable risk factors. Regular medical check-ups and awareness of any unusual lumps or masses can aid in early detection and treatment. Maintaining a healthy lifestyle is always beneficial for overall health, but it does not specifically prevent hibernoma.

Hibernoma is a rare, benign tumor arising from brown fat tissue. It typically presents as a painless mass and is diagnosed through imaging and biopsy. Surgical removal is the treatment of choice, with an excellent prognosis and low risk of recurrence. The cause of hibernoma is not well understood, and it occurs sporadically without known risk factors.

If you have been diagnosed with a hibernoma, it's important to know that this is a benign condition. The tumor is not cancerous and does not spread to other parts of the body. Treatment usually involves surgical removal, which is highly effective. After surgery, most patients recover fully and do not experience any further issues. If you notice any new or unusual lumps, it's always a good idea to consult with your healthcare provider for evaluation.

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