Axillary hibernoma: review of the literature with report of a case examined angiographically

Hibernoma in the thoracic back muscle accompanied by neurilemmoma

Hibernoma is a very rare, benign soft fatty tumor that derived from remnants of fetal brown tissue. The following case of hibernoma break out occurred from a patient who had received surgical resection of neurilemmoma. There has never been a case that reported about hibernoma accompanied by neurilemmoma. It is anticipated that this experience would be helpful to other physicians who are interested in this rare type of tumor.

Hibernoma: Intense Uptake on F18-FDG PET/CT

Hibernoma is a rare benign but metabolically active tumor of brown fat origin, that can have cross-sectional imaging characteristics similar to those of other fat-containing tumors, such as lipomas and liposarcomas, and its presence can lead to false-positive interpretation by exhibiting increased F18-fluorodeoxyglucose (F18-FDG) activity. A 46-year-old woman was diagnosed with dermatofibrosarcoma protuberans underwent F18-FDG positron emission tomography/computed tomography (PET/CT) for detecting recurrence after excision. F18-FDG PET/CT showed incidental intense uptake in the back in addition to increased F18-FDG uptake at the previous lesion site. To our knowledge, this is the first case report of intense F18-FDG uptake in hibernoma in Korea.

Spindle-cell hibernoma: a clinicopathologic comparison of this new variant

Spindle-cell hibernoma is 1 of 4 histologic variants of hibernomas, which are rare lipomatous tumors distinguished from other lipomas by their brown fat component. This article presents a case of a spindle-cell hibernoma that developed in the groin of a 58-year-old man, and is 1 of only 5 known cases of spindle-cell hibernoma published in the scientific literature. Minimal information is available regarding the clinicopathologic characteristics of the 4 hibernoma variants: typical, lipoma-like, myxoid, and spindle-cell. Spindle-cell hibernoma is believed to be the rarest variant, accounting for approximately 2% of hibernomas. The spindle-cell variant predominantly develops in the fourth and fifth decades, with an average age at diagnosis of 42.5 years (range, 28-59 years). It has a male predilection of 4:1. Previously reported only in the posterior neck and scalp, the groin is now added to the sites of spindle-cell hibernoma occurrence. Our patient's tumor demonstrated low-attenuation on computed tomography and contained moderately-attenuating internal septae. Histologically, in addition to the multivacuolated brown fat component common to all hibernomas, spindle-cell hibernoma has a spindle-cell element without vacuolization that is CD34 positive. No prior treatment details are available on this particular variant. Our patient was treated by marginal excision and was disease free through 13 months of follow-up.

Dumbbell-shaped thoracic hibernoma: computed tomography and magnetic resonance imaging findings

Hibernoma is an uncommon, benign soft tissue tumor that arises in brown adipose tissue. The computed tomography (CT) and magnetic resonance imaging (MRI) findings of hibernomas are similar to those of well-differentiated liposarcoma or angiolipoma. We report the unique appearance of a rare thoracic wall hibernoma, which appeared as a dumbbell-shaped lipomatous tumor across an intercostal region. A dynamic contrast-enhanced study on MRI revealed early enhancement, which corresponded to the branching low-signal intensity on T2-weighted images of the mass.

Subpleural Hibernoma

Here we report the case of a 41-year-old man with an asymptomatic, 5-cm, pleural-based mass excised by thoracoscopy. We also review the clinical, radiologic, and pathologic features of hibernomas.

Hibernoma: a case report demonstrating usefulness of MR angiography in characterizing the tumor

Hibernoma is a rare, benign soft-tissue tumor composed of brown fat. In the past, there has been an extensive discussion of the CT attenuation and MRI signal characteristics of hibernomas. However, recent reports have focused upon the tumor vascularity of hibernomas. We describe the only case in the literature which utilizes state of the art contrast enhanced MR angiography to clearly characterize the surface and intratumoral vessels to help confirm the diagnosis of a hibernoma and aid in the preoperative planning.

Hibernoma: MRI features in eight consecutive cases

AIM

To describe the preoperative magnetic resonance imaging findings of eight histologically-proven cases of hibernoma.

MATERIALS AND METHODS

The site, size, and signal characteristics of eight consecutive hibernomas were retrospectively assessed on T1-weighted spin-echo and short T1 inversion recovery (STIR)/fat-saturated T2-weighted fast spin echo magnetic resonance images. Four patients also had gadolinium-enhanced fat-saturated T1-weighted spin echo imaging. Patient age and sex, and duration of symptoms were recorded.

RESULTS

Three female and five male patients with an average age 36 years (range 16-53 years) were included. Seven lesions occurred in the thigh, four in the anterior compartment and three in the posterior compartment. One lesion occurred superficial to the scapula. All cases demonstrated common magnetic resonance imaging findings of a well-defined, heterogeneous mass, slightly or clearly hypo-intense to subcutaneous fat on T1-weighted spin-echo images, with prominent thin low signal bands throughout the tumour. The lesions failed to fully suppress on STIR or fat-saturated T2-weighted images. Only one of the four contrast-enhanced studies demonstrated increased vascularity in the tumour.

CONCLUSION

The MRI findings of a lesion that is diffusely slightly hypointense to surrounding subcutaneous fat, should prompt the operator to consider hibernoma in the differential diagnosis.

Cervical Hibernoma Demonstrating Uptake on Tc-99m Lymphoscintigraphy

A hibernoma is an uncommon, benign tumor composed of brown adipose tissue. It is a rare but documented cause of neck masses. Hibernomas may be first diagnosed not by clinical examination, but incidentally through radiologic tests assessing the metabolic activity of certain tissues. These tumors are by definition benign entities but, given their propensity for growth over time, they require complete extirpation to prevent recurrence. Different radiologic modalities have been used to evaluate hibernomas, including computed tomography scan, magnetic resonance imaging, fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography, and angiography. It is rare for a hibernoma to be discovered through Tc-99m lymphoscintigraphy.

Recurrence and bleeding in hibernomas

Hibernomas are rare, benign, soft tissue tumors of brown fat. Despite being benign, we have experienced recurrent hibernomas and cases of significant bleeding at our institution. The current literature contains case reports of recurrence, and one large series that describes pathologic variants but contains little clinical data. We could not find data on bleeding. We hypothesized that recurrence is related to the resection type and/or the pathologic variant. We also postulated that atypical histologic findings correlate with excessive bleeding during excision. We sought to confirm that the MRI features of hibernomas could distinguish them from lipomas yet place them among lipomatous tumors. We retrospectively reviewed all hibernomas at our institution over 10 years. There were six hibernomas. Two were removed with a marginal excision and four with an intralesional excision. Two recurred after intralesional surgery. Histologic findings were typical for all patients. An MRI was available on only one patient and showed a fatty tumor that was distinguishable from a lipoma. Recurrences occurred after intralesional but not after marginal excisions. Histology could not predict recurrence. Hibernomas have the potential for significant bleeding during surgical excision, as seen in two of our cases.

LEVEL OF EVIDENCE

Prognostic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

From the archives of the AFIP: benign musculoskeletal lipomatous lesions

Benign lipomatous lesions involving soft tissue are common musculoskeletal masses that are classified into nine distinct diagnoses: lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma or lipoblastomatosis, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell lipoma and pleomorphic lipoma, and hibernoma. Soft-tissue lipoma accounts for almost 50% of all soft-tissue tumors. Radiologic evaluation is diagnostic in up to 71% of cases. These lesions are identical to subcutaneous fat on computed tomographic (CT) and magnetic resonance (MR) images and may contain thin septa. Lipomatosis represents a diffuse overgrowth of mature fat affecting either subcutaneous tissue, muscle or nerve, and imaging is needed to evaluate lesion extent. Lipoblastoma is a tumor of immature fat occurring in young children, and imaging features may reveal a mixture of fat and nonadipose tissue. Angiolipoma, myolipoma, and chondroid lipoma are rare lipomatous lesions that are infrequently imaged. Spindle cell and pleomorphic lipoma appear as a subcutaneous lipomatous mass in the posterior neck or shoulder, with frequent nonadipose components. Hibernoma appears as a lipomatous mass with serpentine vascular elements. Benign lipomatous lesions affecting bone, joint, or tendon sheath include intraosseous lipoma, parosteal lipoma, liposclerosing myxofibrous tumor, discrete lipoma of joint or tendon sheath, and lipoma arborescens. Intraosseous and parosteal lipoma have a pathognomonic CT or MR appearance, with fat in the marrow space or on the bone surface, respectively. Liposclerosing myxofibrous tumor is a rare intermixed histologic lesion commonly located in the medullary canal of the intertrochanteric femur. Benign lipomatous lesions may occur focally in a joint or tendon sheath or with diffuse villonodular proliferation in the synovium (lipoma arborescens) and are diagnosed based on location and identification of fat. Understanding the spectrum of appearances of the various benign musculoskeletal lipomatous lesions improves radiologic assessment and is vital for optimal patient management.

Fine-needle aspiration characteristics of hibernoma

BACKGROUND

Hibernoma is a rare, benign lipomatous tumor with features of brown fat. The preoperative diagnosis of hibernoma is difficult at times because its clinical, radiographic, and fine-needle aspiration (FNA) characteristics overlap with those of liposarcoma.

METHODS

The preoperative FNA findings of eight surgically excised hibernomas from seven patients (three men and four women, ages 24-60 years) were reviewed. The cytologic features were compared with the histologic features of the corresponding surgical specimens as well as lipomatous tumors and other lesions that may cause confusion in the differential diagnosis.

RESULTS

The FNA cytologic features of the hibernomas were found to correspond well with their histologic appearance. The FNA findings included small, round, brown fat-like cells with uniform, small cytoplasmic vacuoles and regular, small, round nuclei; delicate branching capillaries; and variable numbers of mature fat cells.

CONCLUSIONS

The FNA cytologic features of hibernoma are characteristic and useful in the preoperative investigation of lipomatous tumors, particularly with regard to excluding a diagnosis of liposarcoma.

Hibernoma of the spermatic cord. The second reported case and literature review

A 23-year-old man was admitted with a 6-month history of a slow-growing mass in the left side of the scrotum. Echography revealed a mixed-density mass that was mainly fatty. The histopathological examination was considered typical of a hibernoma. To our knowledge this is the second case reported.

MRI of a hibernoma

Hibernomas are benign tumors derived from brown fat that most often present as painless, slowly enlarging masses in the interscapular region. Because these lesions have a heterogeneous appearance and contain fat, they mimic liposarcomas on CT and MR, requiring biopsy for definitive diagnosis.

Scalp hibernoma: case report and literature review

Hibernomas are uncommon, benign neoplasms derived from the remnants of fetal brown adipose tissue. A review of the world literature revealed 105 cases, with the interscapular location the most common. Typically, hibernomas are asymptomatic and slow-growing. Adequate treatment usually consists of simple excision. We describe the second documented case of a scalp hibernoma.

Epidural hibernoma as a complication of corticosteroid treatment. Case report

Centripetal fat deposition is a well-recognized consequence of excessive use of corticosteroids, either endogenous or exogenous. Recently, several patients receiving large doses of corticosteroids have suffered compressive myelopathies due to excessive epidural fat collections, labeled "epidural lipomatosis." Two of these have been children, and a third child is reported here. This child was receiving chronic steroids for juvenile rheumatoid arthritis when he presented with such a myelopathy, which was confirmed by metrizamide computerized tomography myelography as well as by surgical exploration. Histological examination revealed that the epidural tissue was a brown-fat tumor or "hibernoma." An epidural hibernoma has not been described previously. The histological and endocrine features of fat in Cushing's syndrome are discussed, and the literature concerning hibernoma and epidural lipomatosis is reviewed.

Hibernomas of the head and neck

Hibernomas are rare tumors derived from brown adipose tissue, a specialized form of fat tissue found in hibernating and nonhibernating animals. Only a minority of reported hibernomas have occurred in the head and neck region. This report describes two cases of cervical hibernomas, one of which was preoperatively diagnosed by the use of fine-needle aspiration biopsy. The clinical and pathologic characteristics of this neoplasm are reviewed. In general, hibernomas are slow-growing tumors with inconclusive evidence for the existence of a malignant variant. A review of the literature supports the conclusion that excision, sparing vital structures, appears to be curative.

Hibernoma. A case report and discussion of a rare tumor

A case report is presented of a large retroperitoneal hibernoma along with the clinical, radiographic, and pathologic findings. Despite the unusual size and location of this hibernoma, the case illustrates the salient features of these rare tumors of brown fat origin. Pitfalls in preoperative diagnosis are discussed. To date, there has been no convincing evidence of malignant potential of this tumor, and total excision remains the treatment of choice.

Cervical hibernoma. Review of the literature and a new case

Hibernoma is the designation for a rare, benign, soft-tissue tumour composed of cells similar to those of brown adipose tissue. Review of the world literature reveals about 80 cases, but only six hibernomas in the cervical region have previously been reported. A case of cervical hibernoma showing descending behaviour is presented, and the histological, histogenetical, and clinical features of hibernomas are discussed. It is stated that the tumours are adequately treated by local excision, as the neoplasms are histologically and clinically benign, but the extensive vascularity may cause troublesome bleeding in some instances.

Hibernoma: ultrastructural observations

A light and electron microscopic study of a hibernoma and a brief discussion of the functional role of brown fat are presented. The multivacuolar cells composing brown fat have central round nuclei with prominent nucleoli. The quantity of mitochondria and lipid droplets in the cytoplasm of the cells varies considerably. The electron microscopic findings of hibernoma include multivacuolated and univacuolated cells with varying numbers of lipid vacuoles, lysosomes, lipofuscin granules, pinocytotic vesicles, and possibly prominent subplasmalemmal condensations. Interesting findings in this case include the presence of amorphous diastase resistant perodic acid (PAS) Schiff positive peripheral cytoplasmic masses which are variable in size and shape. These collections also appear extracellularly. The presence of these masses, presumably composed of neutral mucopolysaccharides, has not, to our knowledge, been recorded previously.