Imaging of soft-tissue tumors

Rare retroperitoneal giant sacral schwannoma: A case report

Schwannomas localized in the sacrum are relatively infrequent, accounting for 1-5% of all spinal axis schwannomas; they present with vague symptoms or are symptomless, so often grow to a considerable size before detection. Sacral schwannomas occasionally present with enormous dimensions, and these tumors are termed giant sacral schwannomas. However, their surgical removal is challenging owing to an abundant vascularity. The present study retrospectively analyzed the clinical and follow-up data of a patient with a giant sacral schwannoma. The patient experienced numbness in the left buttock and lower extremity, with radiating pain in the sole of the foot that had persisted for 3 years. A presacral mass was found by computed tomography examination 6 months after the stool had become thin. A tumor resection was performed using the anterior abdominal approach. A schwannoma was diagnosed by postoperative pathology. The postoperative course was uneventful, with the complete resolution of symptoms during the 21-month clinical follow-up. Overall, the present study reports the case of a giant sacral schwannoma with pelvic pain that was resected without complications and also discusses its successful management. Additionally, the study presents a systematic review of the literature. We consider that the surgical treatment of giant sacral schwannomas with piecemeal subtotal excision can achieve good outcomes, avoiding unnecessary neurological deficits.

Assessment of Calcaneal Spongy Bone Magnetic Resonance Characteristics in Women: A Comparison between Measures Obtained at 0.3 T, 1.5 T, and 3.0 T

BACKGROUND

There is a growing interest in bone tissue MRI and an even greater interest in using low-cost MR scanners. However, the characteristics of bone MRI remain to be fully defined, especially at low field strength. This study aimed to characterize the signal-to-noise ratio (SNR), T2, and T2* in spongy bone at 0.3 T, 1.5 T, and 3.0 T. Furthermore, relaxation times were characterized as a function of bone-marrow lipid/water ratio content and trabecular bone density.

METHODS

Thirty-two women in total underwent an MR-imaging investigation of the calcaneus at 0.3 T, 1.5 T, and 3.0 T. MR-spectroscopy was performed at 3.0 T to assess the fat/water ratio. SNR, T2, and T2* were quantified in distinct calcaneal regions (ST, TC, and CC). ANOVA and Pearson correlation statistics were used.

RESULTS

SNR increase depends on the magnetic field strength, acquisition sequence, and calcaneal location. T2* was different at 3.0 T and 1.5 T in ST, TC, and CC. Relaxation times decrease as much as the magnetic field strength increases. The significant linear correlation between relaxation times and fat/water found in healthy young is lost in osteoporotic subjects.

CONCLUSION

The results have implications for the possible use of relaxation vs. lipid/water marrow content for bone quality assessment and the development of quantitative MRI diagnostics at low field strength.

Impact of CT and MRI in the diagnostic workup of malignant triton tumour-a monocentric analysis and review of the literature

OBJECTIVES

Malignant triton tumours (MTTs) are rare but aggressive subtypes of malignant peripheral nerve sheath tumours (MPNSTs) with a high recurrence rate and 5-year survival of 14%. Systematic imaging data on MTTs are scarce and mainly based on single case reports. Therefore, we aimed to identify typical CT and MRI features to improve early diagnosis rates of this uncommon entity.

METHODS

A systematic review on literature published until December 2022 on imaging characteristics of MTTs was performed. Based on that, we conducted a retrospective, monocentric analysis of patients with histopathologically proven MTTs from our department. Explorative data analysis was performed.

RESULTS

Initially, 29 studies on 34 patients (31.42 ± 22.6 years, 12 female) were evaluated: Literature described primary MTTs as huge, lobulated tumours (108 ± 99.3 mm) with central necrosis (56% [19/34]), low T1w (81% [17/21]), high T2w signal (90% [19/21]) and inhomogeneous enhancement on MRI (54% [7/13]). Analysis of 16 patients (48.9 ± 13.8 years; 9 female) from our institution revealed comparable results: primary MTTs showed large, lobulated masses (118 mm ± 64.9) with necrotic areas (92% [11/12]). MRI revealed low T1w (100% [7/7]), high T2w signal (100% [7/7]) and inhomogeneous enhancement (86% [6/7]). Local recurrences and soft-tissue metastases mimicked these features, while nonsoft-tissue metastases appeared unspecific.

CONCLUSIONS

MTTs show characteristic features on CT and MRI. However, these do not allow a reliable differentiation between MTTs and other MPNSTs based on imaging alone. Therefore, additional histopathological analysis is required.

ADVANCES IN KNOWLEDGE

This largest published systematic analysis on MTT imaging revealed typical but unspecific imaging features that do not allow a reliable, imaging-based differentiation between MTTs and other MPNSTs. Hence, additional histopathological analysis remains essential.

Contrast-enhanced ultrasound guided core needle biopsy for soft tissue tumors: Accuracy and applicability

OBJECTIVE

To evaluate the effectiveness of contrast-enhanced ultrasound (CEUS) guided core needle biopsy (CNB) in diagnosing soft tissue tumors (STTs) and to identify the conventional ultrasonography (US) features of STTs that are recommended for CEUS-guided CNB.

MATERIALS AND METHODS

A retrospective study was conducted on 123 patients with surgically confirmed STTs. Before surgeries, all subjects underwent CNB under the guidance of US or CEUS. The histopathological results of surgical specimens were considered as the gold standards. A successful biopsy diagnosis was defined as the pathological subtypes obtained by biopsy consistent with the gold standard. The diagnostic yields were compared between the US and CEUS groups, and the diagnostic yields based on various conventional US features of STTs were also compared between the two groups.

RESULTS

Sixty-seven cases underwent US-guided CNB and fifty-six cases underwent CEUS-guided CNB. The clinical, biopsy, and conventional US characteristics revealed no significant difference between the two groups. The diagnostic yield of the CEUS group was statistically higher than that of the US group (p = 0.011). In the CEUS group, more STTs with the anechoic areas were identified after CEUS examination (p = 0.031). Furthermore, the diagnostic yields based on the conventional US features of STTs, including deep fascia layer (p = 0.010), a maximum diameter ≥5 cm (p = 0.037), rough margin (p = 0.016), heterogeneous echotexture (p = 0.017), and absence of anechoic area (p = 0.013), were significantly different between the two groups, and the CEUS group exhibited higher diagnostic yields.

CONCLUSION

CEUS-guided CNB was found to be an efficient method for STTs diagnosis. It is particularly recommended for STTs with the following conventional US features, including location in deep fascia layer, a maximum diameter ≥5 cm, rough margin, heterogeneous echotexture, or absence of anechoic area.

Prediction of histopathologic grades of myxofibrosarcoma with radiomics based on magnetic resonance imaging

PURPOSE

To develop a radiomics-based model from preoperative magnetic resonance imaging (MRI) for predicting the histopathological grades of myxofibrosarcoma.

METHODS

This retrospective study included 54 patients. The tumors were classified into high-grade and low-grade myxofibrosarcoma. The tumor size, signal intensity heterogeneity, margin, and surrounding tissue were evaluated on MRI. Using the least absolute shrinkage and selection operator (LASSO) algorithms, 1037 radiomics features were obtained from fat-suppressed T2-weighted images (T2WI), and a radiomics signature was established. Using multivariable logistic regression analysis, three models were built to predict the histopathologic grade of myxofibrosarcoma. A radiomics nomogram represents the integrative model. The three models' performance was evaluated using the receiver operating characteristics (ROC) and calibration curves.

RESULTS

The high-grade myxofibrosarcoma had greater depth (P = 0.027), more frequent heterogeneous signal intensity at T2WI (P = 0.015), and tail sign (P = 0.014) than the low-grade tumor. The area under curve (AUC) of these conventional MRI features models was 0.648, 0.656, and 0.668, respectively. Seven radiomic features were selected by LASSO to construct the radiomics signature model, with an AUC of 0.791. The AUC of the integrative model based on radiomics signature and conventional MRI features was 0.875. The integrative model's calibration curve and insignificant Hosmer-Lemeshow test statistic (P = 0.606) revealed good calibration.

CONCLUSION

An integrative model using radiomics signature and three conventional MRI features can preoperatively predict low- or high-grade myxofibrosarcoma.

Rare giant schwannoma of superficial peroneal nerve on the dorsum of foot

Schwannoma is a benign tumour of Schwann cells originating from myelin sheath of axons of the nerves. It is usually seen in the vestibular region, very rarely found in extremity regions. Schwannomas are termed 'Giant' when they measure more than five centimetres in a minimum of one dimension. Giant schwannomas in the foot and ankle region are extremely uncommon. Only eight cases of such a condition are reported. This is a case report of a giant schwannoma found arising from the superficial peroneal nerve in the dorsolateral aspect of the foot. This swelling was excised completely and the diagnosis was confirmed by histopathology.

Reduction in Acquisition Time and Improvement in Image Quality in T2-Weighted MR Imaging of Musculoskeletal Tumors of the Extremities Using a Novel Deep Learning-Based Reconstruction Technique in a Turbo Spin Echo (TSE) Sequence

Background: The aim of this study was to assess the technical feasibility and the impact on image quality and acquisition time of a deep learning-accelerated fat-saturated T2-weighted turbo spin echo sequence in musculoskeletal imaging of the extremities. Methods: Twenty-three patients who underwent MRI of the extremities were prospectively included. Standard T2w turbo inversion recovery magnitude (TIRMStd) imaging was compared to a deep learning-accelerated T2w TSE (TSEDL) sequence. Image analysis of 23 patients with a mean age of 60 years (range 30−86) was performed regarding image quality, noise, sharpness, contrast, artifacts, lesion detectability and diagnostic confidence. Pathological findings were documented measuring the maximum diameter. Results: The analysis showed a significant improvement for the T2 TSEDL with regard to image quality, noise, contrast, sharpness, lesion detectability, and diagnostic confidence, as compared to T2 TIRMStd (each p < 0.001). There were no differences in the number of detected lesions. The time of acquisition (TA) could be reduced by 52−59%. Interrater agreement was almost perfect (κ = 0.886). Conclusion: Accelerated T2 TSEDL was technically feasible and superior to conventionally applied T2 TIRMStd. Concurrently, TA could be reduced by 52−59%. Therefore, deep learning-accelerated MR imaging is a promising and applicable method in musculoskeletal imaging.

Serendipitous Discovery of a Benign Obturator Nerve Schwannoma: Case report with a brief clinical review

Schwannomas are typically benign tumours of the peripheral nerves. However, they seldom arise from the obturator nerve. We report a case of an uncommon swelling (2.5 × 3.5 cm) in a 65-year-old male cadaver, found during a routine dissection session for first Bachelor of Medicine and Surgery students in the Department of Anatomy, Kasturba Medical College, Manipal, India, in 2019. It was seen originating from the left obturator nerve in the pelvis at the level of the sacral promontory. Histopathological investigation revealed a schwannoma. The hypocellular tumour was arranged in a sweeping fascicle pattern with patches of myxoid degeneration. Obturator schwannomas, though rare, can exist in cadavers, as seen in the present case. Hence, it should be considered as a differential diagnosis for clinical cases of pelvic masses and eliminated only after thorough radiological examination. Knowledge about the existence of such schwannomas is therefore essential.

Radiologic-Pathologic Correlation of Primary Retroperitoneal Neoplasms

An earlier incorrect version of this article appeared in print. The online version is correct.

Primary Site Identification of Soft-Tissue Mass: Things to Know in MRI Assessment

The spectrum of soft-tissue mass is varied, including neoplastic and nonneoplastic/inflammatory lesions. However, soft-tissue tumors have similar imaging findings and, therefore, the diagnosis of soft-tissue mass is challenging. Although careful assessment of the internal characteristics on imaging can often narrow the differential diagnoses, the differential diagnosis may be out of the question if identification of the soft-tissue mass origin is missed. The purpose of this article is to review the imaging findings and the essential anatomy to identify the primary site of the soft-tissue mass, and discuss the associated potential pitfalls. In order not to fall into a pitfall, recognition of characteristic imaging findings indicating the origin of the soft-tissue mass and anatomical knowledge of the normal tissue distribution are necessary. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Intrinsic Laryngeal Lipoma Treated with Transoral CO₂ Laser Microsurgery: An Unusual Case Report

Patient: Female, 28-year-old

Final Diagnosis: Intrinsic laryngeal lipoma

Symptoms: Dyspnoea

Medication: —

Clinical Procedure: —

Specialty: Otolaryngology

Schwannoma of the foot: report of four cases and literature review

Schwannoma is a soft tissue tumor that rarely presents in the foot. Patients are usually asymptomatic, but in some cases symptoms typically result from the mass effect and direct involvement of the nerve and surrounding tissue. We report on four consecutive cases. The first patient was a 57-years-old female that referred symptoms similar to the Morton’s neuroma with a mass arising from the medial plantar nerve. The second patient was treated for a schwannoma in the plantar area. The third case was a female with a schwannoma arising from the sural nerve and the fourth patient had a tumor arising from the medial plantar nerve. All patients underwent surgical excision and histological evaluation. No signs of neurological deficit or recurrence were observed at final follow-up. Purpose of the study was to define clinical features, optimal management and outcome of schwannomas of the foot, through an accurate review of the literature. (www.actabiomedica.it)

Probabilistic classification of tumour habitats in soft tissue sarcoma

The purpose of this work is to propose a method to characterize tumour heterogeneity on MRI, using probabilistic classification based on a reference tissue. The method uses maps of the apparent diffusion coefficient (ADC), T₂ relaxation, and a calculated map representing high-b-value diffusion-weighted MRI (denoted simDWI) to identify up to five habitats (i.e. sub-regions) of tumours. In this classification method, the parameter values (ADC, T₂ , and simDWI) from each tumour voxel are compared against the corresponding parameter probability distributions in a reference tissue. The probability that a tumour voxel belongs to a specific habitat is the joint probability for all parameters. The classification can be visualized using a custom colour scheme. The proposed method was applied to data from seven patients with biopsy-confirmed soft tissue sarcoma, at three time-points over the course of pre-operative radiotherapy. Fast-spin-echo images with two different echo times and diffusion MRI with three b-values were obtained and used as inputs to the method. Imaging findings were compared with pathology reports from pre-radiotherapy biopsy and post-surgical resection. Regions of hypercellularity, high-T₂ proteinaceous fluid, necrosis, collagenous stroma, and fibrosis were identified within soft tissue sarcoma. The classifications were qualitatively consistent with pathological observations. The percentage of necrosis on imaging correlated strongly with necrosis estimated from FDG-PET before radiotherapy (R²  = 0.97) and after radiotherapy (R²  = 0.96). The probabilistic classification method identifies realistic habitats and reflects the complex microenvironment of tumours, as demonstrated in soft tissue sarcoma.

Non Lipomatous Benign Lesions Mimicking Soft-tissue Sarcomas: A Pictorial Essay

The incidental finding of soft tissue masses is a challenge for the radiologist. Benign and malignant lesions can be differentiated relying on patient history, symptoms and mostly with the help of imaging. Ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) become fundamental in order to distinguish these lesions but the radiologist needs to know the main characteristics of benign soft tissue masses and sarcomas. Herein, we present a pictorial review of lesions mimicking soft tissue sarcomas features.

Whole-tumor apparent diffusion coefficient (ADC) histogram analysis to differentiate benign peripheral neurogenic tumors from soft tissue sarcomas

BACKGROUND

Apparent diffusion coefficient (ADC) histogram analyses have been used to differentiate tumor grades and predict therapeutic responses in various anatomic sites with moderate success.

PURPOSE

To determine the ability of diffusion-weighted imaging (DWI) with a whole-tumor ADC histogram analysis to differentiate benign peripheral neurogenic tumors (BPNTs) from soft tissue sarcomas (STSs).

STUDY TYPE

Retrospective study, single institution.

SUBJECTS

In all, 25 BPNTs and 31 STSs.

FIELD STRENGTH/SEQUENCE

Two-b value DWI (b-values = 0, 1000s/mm2 ) was at 3.0T.

ASSESSMENT

The histogram parameters of whole-tumor for ADC were calculated by two radiologists and compared between BPNTs and STSs.

STATISTICAL TESTS

Nonparametric tests were performed for comparisons between BPNTs and STSs. P < 0.05 was considered statistically significant. The ability of each parameter to differentiate STSs from BPNTs was evaluated using area under the curve (AUC) values derived from a receiver operating characteristic curve analysis.

RESULTS

The mean ADC and all percentile parameters were significantly lower in STSs than in BPNTs (P < 0.001-0.009), with AUCs of 0.703-0.773. However, the coefficient of variation (P = 0.020 and AUC = 0.682) and skewness (P = 0.012 and AUC = 0.697) were significantly higher in STSs than in BPNTs. Kurtosis (P = 0.295) and entropy (P = 0.604) did not differ significantly between BPNTs and STSs.

DATA CONCLUSION

Whole-tumor ADC histogram parameters except kurtosis and entropy differed significantly between BPNTs and STSs.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

[Imaging and biopsy of soft tissue tumors]

Soft tissue tumors represent a special challenge in interdisciplinary cooperation. Malignant tumors require a multimodal therapy concept so that patient treatment in a specialized tumor center is recommended. The task of the surgeon in close cooperation with the radiologist is the resection of the tumor in sano with the required safety margin. The aim of diagnostic imaging is to describe the primary expansion of the tumor size and a possible tumor infiltration of adjacent compartments. The most important diagnostic imaging for this purpose is magnetic resonance imaging (MRI), especially T1-weighted fat-suppressed gadolinium-enhanced sequences. Together with T2-weighted sequences a reliable differentiation between necrosis and vital tumor tissue is possible, which enables a targeted biopsy of vital tumor tissue. For the differentiation between benign and malignant soft tissue tumors and for determination of histological differentation a core needle biopsy, either computer tomography-guided or under sonographic control and increasingly more by MRI guidance, is currently the gold standard in most tumor centers. A representative biopsy from vital tumor tissue leads to the diagnosis with a very high degree of certainty.

A 3D MR-acquisition scheme for nonrigid bulk motion correction in simultaneous PET-MR

PURPOSE

Positron emission tomography (PET) is a highly sensitive medical imaging technique commonly used to detect and assess tumor lesions. Magnetic resonance imaging (MRI) provides high resolution anatomical images with different contrasts and a range of additional information important for cancer diagnosis. Recently, simultaneous PET-MR systems have been released with the promise to provide complementary information from both modalities in a single examination. Due to long scan times, subject nonrigid bulk motion, i.e., changes of the patient's position on the scanner table leading to nonrigid changes of the patient's anatomy, during data acquisition can negatively impair image quality and tracer uptake quantification. A 3D MR-acquisition scheme is proposed to detect and correct for nonrigid bulk motion in simultaneously acquired PET-MR data.

METHODS

A respiratory navigated three dimensional (3D) MR-acquisition with Radial Phase Encoding (RPE) is used to obtain T1- and T2-weighted data with an isotropic resolution of 1.5 mm. Healthy volunteers are asked to move the abdomen two to three times during data acquisition resulting in overall 19 movements at arbitrary time points. The acquisition scheme is used to retrospectively reconstruct dynamic 3D MR images with different temporal resolutions. Nonrigid bulk motion is detected and corrected in this image data. A simultaneous PET acquisition is simulated and the effect of motion correction is assessed on image quality and standardized uptake values (SUV) for lesions with different diameters.

RESULTS

Six respiratory gated 3D data sets with T1- and T2-weighted contrast have been obtained in healthy volunteers. All bulk motion shifts have successfully been detected and motion fields describing the transformation between the different motion states could be obtained with an accuracy of 1.71 ± 0.29 mm. The PET simulation showed errors of up to 67% in measured SUV due to bulk motion which could be reduced to less than 10% with the proposed motion compensation approach.

CONCLUSIONS

A MR acquisition scheme which yields both high resolution 3D anatomical data and highly accurate nonrigid motion information without an increase in scan time is presented. The proposed method leads to a strong improvement in both MR and PET image quality and ensures an accurate assessment of tracer uptake.

Perspectives in molecular imaging through translational research, human medicine, and veterinary medicine

The concept of molecular imaging has taken off over the past 15 years to the point of the renaming of the Society of Nuclear Medicine (Society of Nuclear Medicine and Molecular Imaging) and Journals (European Journal of Nuclear Medicine and Molecular Imaging) and offering of medical fellowships specific to this area of study. Molecular imaging has always been at the core of functional imaging related to nuclear medicine. Even before the phrase molecular imaging came into vogue, radionuclides and radiopharmaceuticals were developed that targeted select physiological processes, proteins, receptor analogs, antibody-antigen interactions, metabolites and specific metabolic pathways. In addition, with the advent of genomic imaging, targeted genomic therapy, and theranostics, a number of novel radiopharmaceuticals for the detection and therapy of specific tumor types based on unique biological and cellular properties of the tumor itself have been realized. However, molecular imaging and therapeutics as well as the concept of theranostics are yet to be fully realized. The purpose of this review article is to present an overview of the translational approaches to targeted molecular imaging with application to some naturally occurring animal models of human disease.

Case presentations and review of plexiform schwannoma in the foot

Plexiform schwannoma is a soft tissue tumor that rarely presents in the lower extremity. We have reported on 2 cases of plexiform schwannomas that occurred in the foot and ankle. Owing to the relative obscurity of this condition in the lower extremity, we have also provided an overview of plexiform schwannomas and discussed the differences between this and other suspicious nodular soft tissue masses. The first patient was a 38-year-old female, who had a soft tissue mass located on the lateral aspect of her right foot that became symptomatic. The second patient was an 11-year-old male, who had a symptomatic soft tissue mass on the plantar aspect of his right foot. Both patients underwent surgical excision of the tumor.

Massive, well-differentiated liposarcoma of the axilla

We present a case of well-differentiated liposarcoma (WDL) involving the right proximal arm and axilla in a 66-year-old Filipino male. The patient first noticed the lesion 18 years ago, and it subsequently slowly progressed in size. MR and CT imaging interpreted the lesion as likely being a WDL, a diagnosis that was confirmed by histology.

Contrast-enhanced ultrasound findings in soft-tissue lesions: preliminary results

OBJECTIVES

There is currently no widely available, minimally invasive first-level examination that allows physicians to identify soft-tissue lesions that are likely to be malignant. The aim of this pilot study was to explore the potential suitability of dynamic contrast-enhanced ultrasound (DCE-US) for this purpose.

MATERIALS AND METHODS

23 patients were referred to the Veneto Oncological Institute for work-up of superficial soft-tissue lesions. Fourteen lesions were examined with CEUS and enhancement kinetics was analyzed. Subsequently, all lesions were surgically removed and subjected to histological analysis.

RESULTS

The 14 lesions included in the study were histologically classified as malignant (n = 7) or benign (n = 7, including 3 schwannomas). A statistically significant difference between benign and malignant lesions was found in terms of mean times to peak enhancement intensity (p = 0.03) but not mean filling times (FT). When schwannomas were analyzed as a separate group, their mean FT was found to be significantly different from that of the other benign lesions (p = 0.001) and from that of the group comprising other benign lesions as well as malignant lesions (p < 0.005).

CONCLUSIONS

CEUS with analysis of contrast-enhancement kinetics is a relatively low-cost, minimally invasive imaging technique, which appears to be a potentially effective first-level method for identifying suspicious soft-tissue masses.