Non-Radiographic Risk Factors Differentiating Atypical Lipomatous Tumors from Lipomas

Contrast-enhanced ultrasound reveals perfusion differences between benign lipoma and semi-malignant atypical lipomatous tumors: A prospective clinical study

PURPOSE

Soft tissue tumors (STT) are difficult to diagnose accurately, and distinguishing between benign and malignant tumors is challenging. Lipoma is the most common STT, while atypical lipomatous tumors (ALT) can dedifferentiate into malignant lipomatous tumors like grade 1 liposarcoma and require more radical therapy. This study aims to investigate the potential of contrast-enhanced ultrasound (CEUS) to differentiate between lipoma and ALT based on tumor perfusion.

MATERIALS AND METHODS

We prospectively examined 52 patients who were scheduled for biopsy for suspected lipoma or ALT. The CEUS examination was performed using SonoVue as a contrast agent to quantify tumor perfusion using VueBox V7.1 software. Peak enhancement (PE), rise time (RT), wash-in perfusion index (WiPI), and wash-out rate (WoR) were used to assess contrast enhancement inside the STT.

RESULTS

Among 50 tumors examined, 30 were lipomas, and 20 were ALTs. We found significant differences in perfusion between lipomas and ALTs (PE: 49.22 ± 45.75 a.u. vs. 165.67 ± 174.80; RT: 23.86 ± 20.47s vs. 10.72 ± 5.34 s; WiPI: 33.06 ± 29.94 dB vs. 107.21 ± 112.43 dB; WoR: 2.44 ± 3.70 dB/s vs. 12.75 ± 15.80 dB/s; p<.001). ROC analysis of PE resulted in a diagnostic accuracy of 74% for the detection of an ALT, and 77% for the detection of a lipoma.

CONCLUSION

CEUS may enhance the differential diagnosis of benign lipomas and ALTs, with ALTs showing higher levels of perfusion. If larger prospective studies confirm these findings, CEUS could enhance diagnostic accuracy, guide surgical planning, and potentially reduce unnecessary treatments for patients presenting with ambiguous lipomatous tumors like lipoma or ALT.

The value of a new diagnostic strategy for adipocytic soft tissue tumors in adults: A retrospective study

INTRODUCTION

The distinction between lipoma and well-differentiated liposarcoma (WDLPS), or "atypical lipomatous tumor" (ALT), is crucial as it impacts patient management. A group of European experts led by Benjamin Moulin recently issued a consensus report to define the role of radiology in managing these lesions. It describes an algorithm defining the criteria prompting a diagnostic biopsy of deep lipomatous tumors of the limbs and chest wall. The primary aim of this study was to evaluate the algorithm's diagnostic performance.

MATERIALS AND METHODS

Between 2012 and 2019, all biopsies of deep fatty tumors of the limbs or chest wall with a pre-biopsy MRI assessment were recorded at our institution. The MRI scans were reviewed by two radiologists. Each lesion was classified according to biopsy status by applying the algorithm of the European panel. The algorithm's diagnostic performance was assessed by calculating the sensitivity, specificity, positive predictive value and negative predictive value. Inter-rater agreement was also assessed.

RESULTS

Of the 156 tumors in our study, 148 (94.9%) required a biopsy, and the algorithm's sensitivity for detecting ALT/WDLPS was 100% with specificity of 6.3% and a PPV of 20.3%. Inter-rater agreement was almost perfect with a kappa value of 0.882.

CONCLUSION

The European algorithm demonstrates perfect sensitivity, an important criterion for a screening examination such as MRI in this setting. The algorithm's low specificity, however, emphasizes the need for further studies to redefine the optimum size cut-off value, especially for lesions without atypical criteria or an anatomical location at risk of post-surgical recurrence.

A scoring system combining clinical, radiological, and histopathological examinations for differential diagnosis between lipoma and atypical lipomatous tumor/well-differentiated liposarcoma

This study evaluated the diagnostic accuracy of clinical, radiological, and histopathological examinations for differential diagnosis between atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDLS) and lipoma, and aimed to develop a new combined scoring system for the preoperative diagnosis of ALT/WDLS. Eighty-nine lipomas and 56 ALT/WDLS were included and their clinical characteristics, magnetic resonance imaging (MRI) findings, histological findings by hematoxylin and eosin (HE) staining were investigated. Then, univariate and multivariate logistic regression analyses were performed for the findings, and a combined scoring system consisted of predictive factors of ALT/WDLS was developed. The univariate and multivariate logistic regression analyses revealed that tumor location (lower extremity), deep site, size (> 11 cm), thick septa (> 2 mm), enhancement of septa or nodular lesions, and lipoblasts were significantly different for the diagnosis of ALT/WDLS. We developed a combined scoring system based on the six predictive factors (total 0-16 points, the cutoff was 9 points). The area under the curve was 0.945, and sensitivity was 87.6% and specificity was 91.1% by the receiver operating characteristics curve. This combined scoring system does not require special equipment and reagents such as fluorescence in situ hybridization (FISH), and anyone can use it easily in many medical institutions with high diagnostic accuracy.

Recent Advancement in Atypical Lipomatous Tumor Research

After Evans and colleagues identified the lipomatous tumor with a well-differentiated liposarcoma in a subcutaneous location or within a muscle layer, namely, atypical lipomatous tumor (ALT), this malignancy has been investigated to clarify the characteristics of clinical behavior and genomic changes. As one of the important issues for clinicians, it is a hot topic of how to distinguish ALT from benign lipoma in the clinical aspect. Recent studies revealed novel findings to clarify the risk factor for the diagnosis of ALT and molecular targets for the treatment of ALT. Clinical characteristics of superficial-type ALT well reflect the subcutaneous location of the tumor and are slightly different compared to deep-type ALT, such as tumor size. In addition, there has been a recent discovery of novel findings in ALT-related genes, namely, HMG2A (high mobility group protein 2a), YEATS4 (YEATS domain containing 4), and CPM (Carboxypeptidase M). Recent updates on treatment for advanced ALT are well developed including immunotherapy and conducting clinical trials. Finally, this review introduces one of the hot topics of ALT research focused on epigenetic changes: their attention in recent updates on clinical characteristics and the novel discovery of related genes, treatment, and epigenetic modifications in atypical lipomatous tumors.

Lipomas of the Brachial Plexus: A Case Series and Review of the Literature

BACKGROUND

Lipomas are common benign tumors. When they develop in proximity to peripheral nerves, they can cause neurologic symptoms secondary to mass effect. Previous reports have shown symptom resolution after removal of lipomas compressing various upper extremity peripheral nerves. However, brachial plexus lipomas are relatively rare. Our multidisciplinary experience with brachial plexus lipoma resection is reviewed in the largest case series to date.

METHODS

A retrospective chart review of all patients undergoing resection of brachial plexus lipomatous tumors between 2006 and 2016 was performed. Patient demographic data, diagnostic imaging, clinical presentation, operative details, surgical pathology, and clinical outcomes were reviewed.

RESULTS

Twelve brachial plexus lipomatous tumors were resected in 11 patients: 10 lipomas, 1 hibernoma, and 1 atypical lipomatous tumor. The most common tumor location was supraclavicular (50%), followed by axillary (42%), and proximal medial arm (8%). The most common brachial plexus segment involved was the upper trunk (50%), followed by posterior cord (25%), lateral pectoral nerve (8%), lower trunk (8%), and proximal median nerve (8%). Most patients presented with an enlarging painless mass (58%). Of the patients who presented with neurologic symptoms, symptoms resolved in the majority (80%).

CONCLUSIONS

Brachial plexus lipomas are rare causes of compression neuropathy in the upper extremity. Careful resection and knowledge of brachial plexus anatomy, which may be distorted by the tumor, are critical to achieving a successful surgical outcome with predictable symptom resolution. Finally, surveillance magnetic resonance imaging may be warranted for atypical lesions.

Differentiating atypical lipomatous tumors from lipomas with magnetic resonance imaging: a comparison with MDM2 gene amplification status

Background

To evaluate the diagnostic value of MR imaging for the differentiation of lipomas and atypical lipomatous tumors (ALT) in comparison with histology and MDM2 amplification status.

Methods

Patients with well-differentiated lipomatous tumors (n = 113), of which 66 were diagnosed as lipoma (mean age 53 years (range, 13–82); 47% women) and 47 as atypical lipomatous tumor (ALT; mean age 60 years (range, 28–88); 64% women), were included into this study using histology and MDM2 amplification status by fluorescence in situ hybridization (FISH) as standard of reference. Preoperative MR images were retrospectively assessed by two radiologists for the following imaging features: maximum tumor diameter (mm) as well as the affected compartment (intramuscular, intermuscular or subcutaneous), septa (absent, thin (< 2 mm) or thick septa (> 2 mm) with nodular components); contrast enhancing areas within the lipomatous tumor (< 1/3 of the tumor volume, > 1/3 of the tumor volume);

Results

Of the 47 patients with ALT, 40 (85.1%) presented thick septa (> 2 mm) and this finding significantly increased the likelihood of ALT (OR 6.24, 95% CI 3.36–11.59; P < 0.001). The likelihood of ALT was increased if the tumor exceeded a maximum diameter of 130.0 mm (OR 2.74, 95% CI 1.82–4.11, P < 0.001). The presence of contrast enhancement in lipomatous tumors significantly increased the likelihood of ALT (Odds ratio (OR) 2.95, 95% confidence interval (CI) 2.01–4.31; P < 0.001). Of the lipomas, 21.1% were located subcutaneously, 63.6% intramuscularly and 15.2% intermuscularly. On the other hand, none of the ALTs were located subcutaneously, the majority was located intermuscularly (87.3%) and a small number of ALTs was located intramuscularly (12.7%).

Conclusions

Our results suggest that using specific morphological MR imaging characteristics (maximum tumor diameter, thick septa and contrast enhancement) and the information on the localization of the lipomatous tumor, a high sensitivity and substantial specificity can be achieved for the diagnosis of lipomas and ALTs.

Lipoma in dogs under primary veterinary care in the UK: prevalence and breed associations

Background

Lipomas are masses of mesenchymal origin, comprising of adipocytes, and are often clinically unremarkable but can be alarming to owners. Although lipomas are reportedly common in dogs, no studies have specifically investigated risk factors associated with their occurrence. This study was a large-scale retrospective analysis of electronic patient records of dogs attending practices participating in VetCompass™. Univariable and multivariable logistic regression methods were used to evaluate associations between risk factors and primary-care veterinary diagnosis of lipoma.

Results

From 384,284 dogs under veterinary care during 2013 at 215 primary practice clinics in the UK, there were 2765 lipoma cases identified giving a one-year prevalence of 1.94% (95% CI: 1.87–2.01). Breeds with the highest lipoma prevalence included Weimaraner (7.84%, 95% CI 6.46–9.40), Dobermann Pinscher (6.96%, 95% CI 5.67–8.44), German Pointer (5.23%, 95% CI 3.93–6.80), Springer Spaniel (5.19%, 95% CI 4.76–5.66), and Labrador Retriever (5.15%, 95% CI 4.90–5.41). Dogs with an adult bodyweight equal or higher than their breed/sex mean had 1.96 (95% CI 1.81–2.14, P <  0.001) times the odds of lipoma compared with dogs that weighed below their breed/sex mean. The odds of lipoma increased as adult bodyweight increased. Increased age was strongly associated with increasing odds of lipoma. Compared with dogs aged 3.0 to < 6.0 years, dogs aged 9.0 - < 12.0 years had 17.52 times the odds (95% CI 14.71–20.85, P <  0.001) of lipoma. Neutered males (OR: 1.99, 95% CI 1.69–2.36, P <  0.001) and neutered females (OR: 1.62, 95% CI 1.37–1.91, P <  0.001) had higher odds than entire females. Insured dogs had 1.78 (95% CI 1.53–2.07, P <  0.001) times the odds of lipoma compared with uninsured dogs.

Conclusions

Lipomas appear to be a relatively common diagnosis in primary-care practice. Certain breeds were identified with remarkably high lipoma prevalence, highlighting the risk that owners should be prepared for. Lipoma predisposition of larger bodyweight individuals within breed/sex suggests that being overweight or obese may be a predisposing factor but would need further work to confirm.

Gastric cancer metastatic to neck lipoma: a case report with imaging consideration

A 71-year-old man visited our hospital for examination of a soft neck mass. Computed tomography and magnetic resonance imaging scans showed a well-circumscribed large lipomatous tumor with multiple nodules inside. Atypical lipomatous tumor or lipoma involving the lymph nodes was considered. Pathological examination of the surgical specimen suggested typical lipoma including multiple metastatic foci from gastric cancer. Subsequent endoscopy revealed a gastric tumor, which was histologically proven to be signet-ring cell carcinoma. Considering these findings, this case was diagnosed as tumor-to-tumor metastasis to lipoma. We present the first such case with imaging and clinical characteristics.