The Values and Limitations of FDG-PET/CT for Diagnosis of Hibernoma

A Rare Case of Vulvar Hibernoma Treated With Resection

Hibernoma is a rare benign neoplasm of brown adipose tissue most frequently involving the thigh, shoulder, back, and neck. Differentiating this benign entity from other lipomatous tumors such as well-differentiated liposarcoma is essential, given the different surgical approaches and prognosis associated with each diagnosis. It is helpful for the radiologist to recognize the uncommon locations of hibernoma, as well as characteristic imaging features, in order to properly include it in the differential considerations. Here we present a rare case of symptomatic vulvar hibernoma in a 25-year-old woman treated with surgical excision. 

Intrascrotal hibernoma mimicking liposarcoma: A case study

Hibernoma is a rare benign lipomatous tumor derived from brown fat, which is typically found in infants. Specifically, intrascrotal hibernoma is extremely rare with only one case reported to date. We encountered the second case, which was successfully treated with surgical resection without any recurrence at 3 years.

The patient was first misdiagnosed with an intrascrotal liposarcoma preoperatively. Preoperative usefulness of imaging modalities to discriminate hibernomas and liposarcomas is limited due to lack of specific features of hibernomas with its rarity. Here, we report a case of intrascrotal hibernoma in addition to a current literature review.

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Hibernoma is a rare benign lipomatous tumor.

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Specifically, intrascrotal hibernoma is extremely rare with only one case reported to date.

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Preoperative discrimination of hibernomas and lipomatous tumors is difficult.

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A histopathological examination is needed to make a definitive diagnosis of hibernomas.

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Immunohistochemical and FISH analyses should be performed, in cases of intrascrotal hibernoma.

18F-FDG PET/CT imaging features of lipomatous tumors

The objective was to evaluate the ¹⁸F-FDG PET/CT characteristics of lipomatous tumors, and examine features helpful in differentiating benign from malignant tumor subtypes. Patients undergoing ¹⁸F-FDG PET/CT from 01/2005 to 03/2018 with subsequent pathologically confirmed liposarcoma, lipoma, or hibernoma were retrospectively reviewed with IRB approval. A variety of imaging features, including metabolic activity and tumor morphology were noted. 67 tumors were included: 13 lipomas, five hibernomas, 16 atypical lipomatous tumors, 16 dedifferentiated liposarcomas, 15 myxoid liposarcomas, and two pleomorphic liposarcomas. There were 42 males and 23 females, mean age 58.8 ± 13.6 years. Mean SUVmax of lipomas measured 0.8 ± 0.2, atypical lipomatous tumors 2.3 ± 1.2, myxoid liposarcomas 3.0 ± 1.0, hibernomas 11.9 ± 8.4, pleomorphic liposarcomas 13.5 ± 2.9, and dedifferentiated liposarcomas 16.3 ± 11.4. There was no significant difference in metabolism between benign and malignant subtypes (SUVmax 3.9 ± 6.5 versus 7.6 ± 9.2, P = 0.13). There was a significant difference in metabolism between low- and high-grade liposarcoma (SUVmax 2.5 ± 1.2 versus 12.8 ± 10.8, P = 0.0001). 10/13 lipomas, 2/5 hibernomas, and 2/16 atypical lipomatous tumors had no internal soft tissue content. There are overlapping ¹⁸FDG PET/CT features of benign and malignant lipomatous tumors. While liposarcoma grade correlates with SUVmax, malignant lesions (myxoid liposarcomas and atypical lipomatous tumors) may present with low FDG uptake and benign lesions (hibernomas) may demonstrate high metabolic activity. In some instances, a combination of metabolic and morphologic characteristics may narrow the differential diagnosis, or even be diagnostic.

Gastric hibernoma: a novel location and presentation of a rare tumor

We present a case of gastric hibernoma, an unusual tumor with a location novel to the literature. A 39-year-old female presented with one year of upper gastrointestinal bleeding and dysphagia. Gastroenterology performed an esophagogastroduodenoscopy with ultrasound and identified a 6 cm mass within the muscularis propria of the antrum. Computed tomography demonstrated a 9.7 × 7.8 × 4.8 cm³ heterogeneous antral mass with internal septa. A distal gastrectomy with Bilroth I gastroduodenostomy was performed with 4 cm proximal and 2 cm distal margins. Excision was appropriate to make the diagnosis, exclude malignancy, and remove a symptomatic mass. Hibernoma was confirmed by histopathology. These are rare tumors of brown fat named for their resemblance to the thermogenic tissue found in hibernating animals. They typically present as a slowly enlarging mass of the thigh or shoulder. To our knowledge, this is the first presentation of a hibernoma as a submucosal gastric mass.

A Rare Case of Hibernoma Occasionally Identified by 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in a Patient with Lung Cancer

Hibernoma is a benign tumor arising from brown fat tissue. Conventional imaging techniques are not able to differentiate it from other benign lesions or malignant fatty tumors. We report the case of a 73-year-old patient who underwent a thorax computed tomography (CT) and was then referred to our department for metabolic assessment of a solitary lung nodule. An F18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) scan was performed and demonstrated, in addition, a highly metabolic fat-containing lesion mimicking a malignant fatty tumor in the left great pectoralis muscle. The lesion was excised and resulted to be a hibernoma. This case shows that hibernoma can appear as a malignant-like lesion on 18F-FDG-PET/CT scan as per other imaging techniques, and the grade of FDG uptake does not accurately reflect malignancy in this fat-containing tumor. However, 18F-FDG-PET/CT with its whole-body scanning capability may represent a useful imaging tool in identifying, in the course of an imaging study for oncological evaluation, additional incidental findings such as benign fat-containing lesions that may require a surgical approach.