Hibernoma: Intense Uptake on F18-FDG PET/CT

Case Report: All that glitters is not cancer; perihepatic hibernoma with fluctuating FDG uptake on PET/CT

Hibernomas are rare brown fat tumors that garnered attention in the literature with the increasing use of [18F] Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography ([18F] FDG PET/CT) for the staging workup and follow-up of solid malignancies. Despite being benign tumors, they exhibit high metabolic activity due to their thermogenic nature, leading to significant radiotracer uptake on functional imaging. This can pose a challenge in differentiating them from the malignant lesions, especially the fat-containing malignancies such as liposarcoma. Hibernomas are typically found in the thigh, shoulder, back, and neck. Here, we present a unique case of Hibernoma in a patient undergoing PET/CT for melanoma follow-up in an unusual perihepatic location. To the best of the authors' knowledge, this represents the first reported case of a perihepatic hibernoma in the literature. The report also offers a literature review on hibernomas, including the influence of ambient temperature on their metabolism, diagnostic challenges, management strategies, and reports of hibernomas detected on functional imaging with a range of radiotracers. These observations could serve as a valuable clue in identifying hibernomas, potentially aiding in avoiding unnecessary biopsies or resections.

Incidental Detection of Lipomatous Hypertrophy of the Interventricular Septum on FDG PET/CT

ABSTRACT

Cardiac lipomatous hypertrophy is a rare benign condition almost exclusively involving the interatrial septum. Interventricular septum involvement is seldom noted, with only a few documented case reports demonstrating the finding on various modalities such as ECHO, CT, and MRI. FDG PET can be a surrogate marker for lipomatous hypertrophy of the interventricular septum. Here, we describe a case of incidentally detected lipomatous hypertrophy of the interventricular septum on FDG PET/CT in a patient with squamous cell carcinoma of the oropharynx.

Positron Emission Tomography/Computed Tomography Transformation of Oncology: Musculoskeletal Cancers

The past 25 years have seen significant growth in the role of positron emission tomography/computed tomography (PET/CT) in musculoskeletal oncology. Substantiative advances in technical capability and image quality have been paralleled by increasingly widespread clinical adoption and implementation. It is now recognized that PET/CT is useful in diagnosis, staging, prognostication, response assessment, and surveillance of bone and soft tissue sarcomas, often providing critical information in addition to conventional imaging assessment. As individualized, precision medicine continues to evolve for patients with sarcoma, PET/CT is uniquely positioned to offer additional insight into the biology and management of these tumors.

The Usefulness of Short-Interval Sequential FDG PET/CT Studies in Defining the Benignity of Hypermetabolic Lipomatous Tumor

ABSTRACT

We present an interesting case of incidentally detected lipomatous tumor in an oncological patient that could result in a false-positive interpretation by exhibiting intense FDG activity similar to that of a malignant neoplasm. Careful evaluation of FDG uptake changes on sequential short-interval PET/CT studies was helpful in defining the benign nature of the tumor as the hypermetabolism was gradually disappearing obviating the need for a major surgery.

Fat-containing pelvic lesions in females

Pelvic tumors are common in females and have a broad differential diagnosis. The clinical management of pelvic tumors varies widely-from observation to surgical resection-and imaging plays a pivotal role in diagnosis and clinical decision-making in these cases. In particular, imaging can help determine the organ of origin and tissue content of these tumors, which are the most important steps to narrowing the differential diagnosis. Fat has a characteristic appearance and is often easily identified on ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI). The amount and distribution of intralesional fat varies in different types of tumors. Macroscopic intralesional fat is often easily recognized by its hyperechoic appearance on US and low attenuation on CT similar to subcutaneous fat. On MRI, macroscopic fat is hyperintense on T1-weighted (T1W) images, with characteristic signal loss on fat-saturated sequences and India-ink artifact on opposed-phase T1W images. Macroscopic fat is the hallmark of teratomas, which are the most common ovarian neoplasms. Uterine lipoleiomyomas, peritoneal loose bodies, intraperitoneal and extraperitoneal primary lipomatous tumors such as lipoma and liposarcomas, and extra-adrenal myelolipomas are other pelvic masses distinguished by the presence of macroscopic fat. However, the imaging diagnosis of pelvic masses containing minimal or microscopic fat, such as immature ovarian teratomas, steroid cell ovarian neoplasms, and extramedullary hematopoiesis, can present a diagnostic challenge owing to their nonspecific appearance on US or CT. Obtaining MRI with in-phase and opposed-phase dual-echo T1W sequences and depicting chemical shift artifacts can be helpful in distinguishing these lesions.

Incidental Finding of Hibernoma in Prostate-Specific Membrane Antigen PET/CT

ABSTRACT

We reported the case of a 76-year-old man followed up since 2008 for a prostatic adenocarcinoma with pelvic and retroperitoneal nodes. He was initially treated by hormonotherapy with a good biological response. Twelve years after, he demonstrated an increased PSA level up to 10.2 ng/mL. He underwent a 68Ga-PSMA PET/CT, which shown an intense uptake by a left iliac extern mass, suspected of recurrence. The histology concluded in a hibernoma.

Femoral nerve compression caused by a hibernoma in the right thigh: a case report and literature review

BACKGROUND

A hibernoma, also known as a brown fat tumor, is a rare benign soft tissue tumor, which originates from brown adipose tissue remaining in the fetus after the gestational period. It is often detected in adult men, presenting as a painless slow-growing mass. Hibernomas of the thigh have been reported; however, motor and sensory disorders caused by the tumors compressing the femoral nerve have not been reported. We report a case of a histopathologically proven hibernoma that induced femoral mononeuropathy.

CASE PRESENTATION

A 26-year-old man was admitted to the hospital due to a mass, approximately 11.0 × 9.0 × 4.0 cm in size, that had developed 5 years ago in the anterolateral aspect of the proximal thigh. Furthermore, he had a history of hypoesthesia 1 month prior to his admission. He had signs and symptoms of both a motor and sensory disorder, involving the anterior aspect of the right thigh and the medial aspect of the calf, along the distribution of the femoral nerve. During surgery, the femoral nerve was found to be compressed by the giant tumor. The resultant symptoms probably caused the patient to seek medical care. Marginal resection of the mass was performed by careful dissection, and the branches of the femoral nerve were spared. Histopathology examination showed findings suggestive of a hibernoma. At the 4-month follow-up, no femoral nerve compression was evident, and local tumor recurrence or metastasis was not found.

CONCLUSIONS

Asymptomatic hibernomas do not require treatment; however, in cases of hibernomas with apparent symptoms, complete marginal surgical excision at an early stage is a treatment option because it is associated with a low risk of postoperative tumor recurrence.

Axillary Hibernoma in woman with Lobular breast cancer and MEN1 syndrome: A case report

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There is no uniformly accepted indication to perform the correct management of hibernoma.

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Only the complete surgical resection of the known axillary lesion, could be diagnostic and, in most case, curative.

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A full multidisciplinary team is essential to focus on all aspects for the management of hibernoma and MEN-1 syndrome.

Introduction

The present study reports the case of an axillary hibernoma in a patient with lobular homolateral breast cancer and multiple endocrine neoplasia type1 (MEN-1).

Hibernoma is a rare benign adipose tissue tumor, and usually manifests as a slowly growing and painless rubbery mass.

These tumors can arise in various sites, but mammary hibernomas remain extraordinarily uncommon. Although hibernomas are metabolically active and therefore “glucose-avid” on fluorodeoxyglucose CT-positron emission tomography (FDG CT-PET), imaging alone is inadequate in providing a reliable diagnosis and definitive differential diagnosis from other malignancy. Only complete surgical excision is diagnostic and, in most cases, curative.

Presentation of case

A 42-years-old woman was followed for MEN-1 syndrome associating with hyperparathyroidism, insulinoma, non-secretory adrenal adenoma and thyroid lump. A FDG CT-PET found high glucid hypermetabolism in thickened elongated area on the front axillary line.

Hibernoma was diagnosed after realization of prophylactic left mastectomy, homolateral sentinel lymph node biopsy and exeresis of the known axillary lesion.

Discussion

Clinical importance lies in distinguishing hibernoma from other benign and malignant breast neoplasms, as well as inflammatory conditions that come into the histologic or radiologic differential. Hibernoma is not currently classified as a non-endocrine tumor related to MEN1, but this association could be not fortuitous for the linkage between modification of Menin protein function and pathogenesis of hibernomas.

Conclusion

Our case deserves extraordinary attention because, not only it’s a case of MEN1 syndrome associated with hibernoma, but in the context of this lesion there are multiple micro-foci of infiltrating lobular carcinoma.

Quantitative Musculoskeletal Tumor Imaging

The role of quantitative magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) techniques continues to grow and evolve in the evaluation of musculoskeletal tumors. In this review we discuss the MRI quantitative techniques of volumetric measurement, chemical shift imaging, diffusion-weighted imaging, elastography, spectroscopy, and dynamic contrast enhancement. We also review quantitative PET techniques in the evaluation of musculoskeletal tumors, as well as virtual surgical planning and three-dimensional printing.

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.

Pure Uterine Lipoma on 18FDG PET/CT: Rare But Easy to Diagnose

Tumors of the uterus are extremely uncommon. Pure lipomas of the uterus are very rare, and only a few cases have been reported. We are presenting a case of a post-menopausal lady, a survivor of right breast cancer who had an 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18FDG PET/CT) for evaluation of a suspected right lung nodule. The scan was negative for hypermetabolic abnormality. However, a hypodense and non-metabolic lesion was seen in the fundus of the uterus. On subsequent hysterectomy, it was found to be a pure lipoma.

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.

Fat-Containing Hypermetabolic Masses on FDG PET/CT: A Spectrum of Benign and Malignant Conditions

OBJECTIVE

This article focuses on identifying the imaging appearances of hypermetabolic fatty masses and masslike lesions on PET/CT and understanding the diagnostic challenges radiologists may face while interpreting findings of these lesions on PET/CT. This article provides an approach to aid in the diagnosis of these lesions and the appropriate management of patients.

CONCLUSION

Both malignant and benign fat-containing masses and masslike lesions can show hypermetabolic activity on PET/CT. Although the differential diagnosis is broad, clinical history, anatomic location, and knowledge of anatomic variants and imaging features can help radiologists avoid misinterpretation of benign fatty lesions as malignancy.

Hibernoma Showing High Uniform Accumulation on an 18F-Fluorodeoxyglucose Positron Emission Tomography Scan: A Case Report

Background

Hibernoma is a rare, benign, soft tissue tumor arising from brown fat that cannot be distinguished from other lipogenic tumors on computed tomography and magnetic resonance imaging (MRI) scans. On the other hand, the image of hibernoma on ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) is different from that of other lipogenic tumors. However, fewer studies have investigated the typical features of hibernoma on PET scans. We present the case of a hibernoma that was incidentally detected on ¹⁸F-FDG-PET.

Case Presentation

A 48-year-old Asian man underwent ¹⁸F-FDG-PET for routine follow-up of gastric cancer. The patient reported a painless soft mass on the upper arm that had persisted for several years. On ¹⁸F-FDG-PET, the mass showed a maximum standardized uptake value of 9.6. The mass showed high intensity on T1- and T2-weighted MRI scans, and showed focally enhanced septa after gadolinium administration. The mass was surgically resected. Histopathologically, the mass was composed of brown adipose cells characteristic of hibernoma. His postoperative course was uneventful, and there was no local recurrence at the final 24-month follow-up.

Conclusion

Hibernoma showed strong uniform accumulation on ¹⁸F-FDG-PET, suggesting that ¹⁸F-FDG-PET would be a useful modality for the differential diagnosis of hibernoma versus other lipogenic tumors.

Top five lesions that do not need referral to orthopedic oncology

Patients with potential bone and soft tissue tumors can be challenging for orthopedic surgeons. Lesions that appear benign can still create anxiety for the clinician and patient. However, attention to a few key imaging and clinical findings is enough to correctly diagnose five of the most common bone and soft tissue lesions: lipoma, enchondroma, osteochondroma, nonossifying fibroma, and Paget disease. Accurate identification of these lesions should be within the scope of most orthopedic surgeons and, because most of these patients will not need surgical treatment, referral to orthopedic oncology will not typically be required.