Subpleural Hibernoma

A large thigh hibernoma in a 23-years-old man: Case report

INTRODUCTION AND IMPORTANCE

Hibernomas are benign soft tissue tumors containing prominent brown adipocytes that resemble normal brown fat, they occur in a wide age range (from 2 to 75 years) and make up for about 1 % of all adipocytic tumors <2 % of benign fatty neoplasms. They have traditionally been regarded as benign tumors with no potential for malignancy; due to their similarity in clinical and radiographical presentation, they are often misdiagnosed as malignant tumors like liposarcomas. While these tumors are generally considered non-malignant, their distinctive characteristics and uncommon occurrence make them an intriguing subject for medical study.

CASE PRESENTATION

This article describes the clinical, radiographic, and histologic features of a young patient with a thigh hibernoma compressing the obturator nerve.

CLINICAL DISCUSSION

Hibernomas are more likely to develop in brown fat-enriched areas in newborns, such as the neck, scapular area, armpit, chest, and retroperitoneum. Increased awareness among clinicians and pathologists, coupled with advances in imaging and immunohistochemistry, has enhanced our ability to accurately identify and treat these intriguing tumors.

CONCLUSION

The rarity of hibernomas together with the close resemblance of their radiological features to those of malignant tumors like liposarcomas or atypical lipomatous tumors, make these lesions extremely difficult to identify and often misdiagnosed. Continued research is essential to further our understanding this neoplasm and refine diagnostic and therapeutic approaches.

Hibernoma Mimicking Atypical Lipomatous Tumor: 64 Cases of a Morphologically Distinct Subset

Hibernoma is a benign adipocytic tumor with predilection for subcutaneous tissue of the thigh, upper trunk, and neck of middle-aged adults. 11q13 rearrangement resulting in MEN1/AIP codeletion is characteristic. Hibernomas are composed, in varying proportions, of brown fat cells, mature adipocytes, and microvacuolated lipoblast-like cells. Examples containing predominantly multivacuolated lipoblast-like cells are uncommon and distinction from atypical lipomatous tumor (ALT) is important for clinical management. We herein present the clinicopathologic features of 64 hibernomas histologically mimicking ALT. MDM2 and CDK4 immunohistochemistry as well as MDM2 fluorescence in situ hybridization were performed in a subset of cases. Clinical and follow-up information were obtained from referring pathologists. Thirty-four patients were male and 30 female, with a median age of 43 years (range, 24 to 78 y). The tumors were well circumscribed and mostly deeply located (53/64 cases, 83%) with a median tumor size of 12.9 cm (range, 3.5 to 23 cm) and predilection for the thigh (42/64 cases, 66%). Histologically, large cells with prominent lipoblast-like cytoplasmic fatty vacuoles and small central nuclei were present to a prominent degree in all cases, along with mature univacuolated adipocytes and smaller numbers of large, finely vacuolated cells with eosinophilic granular cytoplasm. Nuclear atypia and mitoses were absent. None of the 39 cases tested showed CDK4 and MDM2 overexpression or MDM2 amplification. Follow-up, available for 16/64 cases (median, 47 mo; range, 1 to 165 mo), revealed no recurrences or metastases. Hibernoma mimicking ALT shows predilection for deep soft tissue, especially in the thigh. These tumors behave in a benign manner and MDM2/CDK4 negativity may be useful in excluding ALT.

Immunohistochemical diagnostic of hibernoma in dog

The diagnosis of hibernoma is uncommon in veterinary medicine. In this report, we present an attempt to confirm hibernoma diagnosed in dogs by applying immunohistochemical tests routinely used in human pathology i.e. antibodies specific to protein S100, protein CD31, or smooth muscle actin (SMA).

Pediatric cervicomediastinal hibernoma: a case report

Hibernoma is a rare lipomatous tumor of brown fat origin. Though uniformly benign in nature these tumors may cause symptoms secondary to extrinsic compression of neighboring structures. Hibernomas may be found anywhere that normal fetal brown fat may be located but are most commonly located in the thigh. We present a case of a hibernoma presenting as an unusual cervicomediastinal mass in a 6-year-old male. This mass was discovered during a diagnostic chest x-ray for pneumonia and treated by resection. Complete surgical resection is considered curative. Hibernoma should be considered in the differential diagnosis of any lipomatous tumor.

Cervical hibernoma, a rare, benign tumor: case report

Hibernomas are rare, benign tumors that contain neoplastic cells that are histologically similar to those of brown adipose tissue. The most common sites of these tumors have been the back and thighs; head and neck involvement has been rare. We describe the case of a 54-year-old woman who presented with a 1-year history of a large, asymptomatic, lateral neck mass. Based on imaging findings and fine-needle aspiration cytology, a hibernoma was suspected, although a liposarcoma could not be ruled out prior to surgery. The mass was completely resected. On postoperative analysis, the tumor was grossly and microscopically consistent with a cervical hibernoma. Although hibernomas are rare, they are important entities and should be considered in the differential diagnosis of a soft-tissue mass of the head or neck.

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.

Intrathoracic hibernoma: report of two cases

Hibernomas are uncommon benign soft tissue tumours mimicking brown fat. The most common anatomic locations include the neck, axilla, mediastinum, periaortic and perirenal zones. Intrathoracic and in particular pleural locations are exceptional. We report two cases of intrathoracic hibernoma with pleural involvement treated by surgical resection.