Differentiation of benign from malignant musculoskeletal lesions using MR imaging: pitfalls in MR evaluation of lesions with a cystic appearance

Society of skeletal radiology position paper - recommendations for contrast use in musculoskeletal MRI: when is non-contrast imaging enough?

The following White Paper will discuss the appropriateness of gadolinium administration in MRI for musculoskeletal indications. Musculoskeletal radiologists should consider the potential risks involved and practice the judicious use of intravenous contrast, restricting administration to cases where there is demonstrable added value. Specific nuances of when contrast is or is not recommended are discussed in detail and listed in table format. Briefly, contrast is recommended for bone and soft tissue lesions. For infection, contrast is reserved for chronic or complex cases. In rheumatology, contrast is recommended for early detection but not for advanced arthritis. Contrast is not recommended for sports injuries, routine MRI neurography, implants/hardware, or spine imaging, but is helpful in complex and post-operative cases.

A case report of primary myxoid liposarcoma mimicking as a parotid cystic lesion

RATIONALE

Myxoid liposarcoma (MLS) is an extremely rare tumor of the salivary gland and it arises from undifferentiated pluripotent mesenchymal cells. We report a rare case of a primary MLS in the parotid gland.

PATIENT CONCERNS

The patient was a 49-year-old female who presented with a hard fixed mass in the left parotid region.

DIAGNOSIS

On computed tomography and MR images, this tumor has a low attenuation center with a thick enhancing wall and ill-defined margins. The absence of high-signal-intensity foci on T1-weighted images makes a MLS indistinguishable from most other soft-tissue masses. Pathologically, the tumor was diagnosed as MLS.

INTERVENTIONS

The patient received total parotidectomy with facial nerve preservation and selective neck dissection.

OUTCOMES

Immediate facial nerve function was House Brackmann Grade III and recovered within 3 months after the surgery. Follow-up period is 57 months and there was no recurrence until now.

LESSONS

In this report, we report a rare case of primary MLS mimicking a cystic lesion of the parotid gland.

Machine Learning in the Differentiation of Soft Tissue Neoplasms: Comparison of Fat-Suppressed T2WI and Apparent Diffusion Coefficient (ADC) Features-Based Models

Machine learning has been widely used in the characterization of tumors recently. This article aims to explore the feasibility of the whole tumor fat-suppressed (FS) T2WI and ADC features-based least absolute shrinkage and selection operator (LASSO)-logistic predictive models in the differentiation of soft tissue neoplasms (STN). The clinical and MR findings of 160 cases with 161 histologically proven STN were reviewed, retrospectively, 75 with diffusion-weighted imaging (DWI with b values of 50, 400, and 800 s/mm²). They were divided into benign and malignant groups and further divided into training (70%) and validation (30%) cohorts. The MR FS T2WI and ADC features-based LASSO-logistic models were built and compared. The AUC of the FS T2WI features-based LASSO-logistic regression model for benign and malignant prediction was 0.65 and 0.75 for the training and validation cohorts. The model's sensitivity, specificity, and accuracy of the validation cohort were 55%, 96%, and 76.6%. While the AUC of the ADC features-based model was 0.932 and 0.955 for the training and validation cohorts. The model's sensitivity, specificity, and accuracy were 83.3%, 100%, and 91.7%. The performances of these models were also validated by decision curve analysis (DCA). The AUC of the whole tumor ADC features-based LASSO-logistic regression predictive model was larger than that of FS T2WI features (p = 0.017). The whole tumor fat-suppressed T2WI and ADC features-based LASSO-logistic predictive models both can serve as useful tools in the differentiation of STN. ADC features-based LASSO-logistic regression predictive model did better than that of FS T2WI features.

Simple Stepwise Approach to Differentiate Cyst-Like Soft-Tissue Masses by Using Time-Resolved Magnetic Resonance Angiography

This retrospective study aimed to differentiate cyst-like musculoskeletal soft-tissue masses by using time-resolved magnetic resonance angiography (MRA). During May 2015 to November 2019, patients with cyst-like soft-tissue masses examined through contrast-enhanced MRI followed by histologic diagnosis were included. The masses were classified into vascular lesions, solid lesions, and true cysts. Size, T1 hyperintensity, T2 composition, perilesional edema, time-resolved MRA, and static internal enhancement were assessed. The time-resolved MRA manifestations were classified into vascular pooling, solid stain, and occult lesion. Imaging predictors for each type of mass were identified through logistic regression and were used to develop a diagnostic flowchart. A total of 80 patients (47 men; median age, 42 years) were included, with 22 vascular lesions, 38 solid lesions, and 20 true cysts. The T2 composition, time-resolved MRA, and static internal enhancement were significantly different among the masses. Vascular pooling on time-resolved MRA was the sole predictor of vascular lesions (odds ratio = 722.0, p < 0.001). Solid stain on time-resolved MRA was the sole predictor of solid lesions (odds ratio = 73.6, p < 0.001). Occult lesion on time-resolved MRA (odds ratio = 7.4, p = 0.001) and absence of static internal enhancement (odds ratio = 80.0, p < 0.001) both predicted true cysts, while the latter was the sole predictor of true cysts after multivariate analysis. A diagnostic flowchart based on time-resolved MRA correctly classified 89% of the masses. In conclusion, time-resolved MRA accurately differentiates cyst-like soft-tissue masses and provides guidance for management.

Imaging musculoskeletal soft tissue infections

Musculoskeletal soft tissue infections are not uncommonly encountered in both the clinic and Emergency Department setting. The clinical diagnosis is not always evident as these infections can have variable presentations depending on the duration and depth of disease extension through the soft-tissue layers. Imaging often plays an important role in diagnosing the infection, defining the extent of involvement, directing tissue sampling, and in monitoring treatment response. After initial radiographs, ultrasound (US) is often the next modality utilized to evaluate patients with suspected soft tissue infections given its low cost, availability, portability, and potential for real-time guidance of fluid aspiration. The widespread use of cross-sectional imaging with magnetic resonance imaging (MRI) and computed tomography (CT) has greatly increased the radiological diagnosis in conditions where US may be limited. In addition, CT and MRI allow a thorough evaluation of disease extension, including assessment of joint spaces, tendons, and osseous changes indicative of bone involvement. This review will focus on the radiological findings of soft tissue infections on US, CT, and MRI.

Case report: urinoma in the proximal thigh mimicking a soft tissue neoplasm

Soft tissue tumors form a heterogeneous group of benign and malignant lesions. Those with a high fluid content may be particularly challenging in diagnosis. We present a 78-year-old man with a dolorous, progressive mass in the adductor region of the lower left extremity. At the end of a long diagnostic pathway, the pseudocystic tumor was eventually identified as a urinoma, caused by a prostatosymphyseal fistula that had occurred as a late complication of transurethral resection of the prostate. Our finding represents a rare variant of soft tissue tumors in the lower extremities, which MR-based urography can help to reveal.

Diagnostic performance of diffusion-weighted (DWI) and dynamic contrast-enhanced (DCE) MRI for the differentiation of benign from malignant soft-tissue tumors

BACKGROUND

A wide range of specificity values for the differentiation of benign and malignant soft-tissue tumors show the limitations of conventional MRI features. The data obtained by quantitative analysis of diffusion-weighted image (DWI) and dynamic contrast-enhanced (DCE) MRIs would provide more objective results, especially in terms of cellularity and perfusion.

PURPOSE

To evaluate the diagnostic efficacies of DWI and DCE MRI for the differentiation of malignant and benign soft-tissue tumors.

STUDY TYPE

Retrospective.

SUBJECTS

In all, 136 patients (68 females, 68 males; age range 18-86 years, mean age 57.2 years) with soft-tissue tumors.

FIELD STRENGTH/SEQUENCE

3 T, DWI, DCE.

ASSESSMENT

Tumor sizes, margins, locations, the presence of involvement in bone or neurovascular bundle, peritumoral edema, heterogeneity, and tumor necrosis were investigated on conventional MR images. On DWIs, visual signal drops were assessed and ADC (apparent diffusion coefficient) values were measured. K^trans , K_ep , V_e , and iAUC values, and time-concentration curve (TCC) types were determined using DCE images.

STATISTICAL TESTS

The data were statistically analyzed to determine the abilities to differentiate benign and malignant tumors using the chi-square test, two-sample t-test, and receiver operating characteristic (ROC) analysis.

RESULTS

Seventy-three cases were malignant and 63 benign. Age (mean ages of benign/malignant tumors, 51.75/61.86 years; P = 0.0002) and gender (F:M = 40:23 [benign], F:M = 28:45 [malignant], P = 0.003) influenced the distinction between benign and malignant. Sizes, margins, neurovascular bundle involvement, peritumoral edema, and heterogeneity of the tumors on conventional MR images and DCE parameters (K^trans , K_ep , V_e , and iAUC, and TCC plots) obtained from focal region of interest within a narrow volume of interest significantly differentiated benign and malignant lesions (all P < 0.0001, except V_e [P = 0.0004]). For DWI with ADC mapping, all ADC values and visually signal drops were also significant (P < 0.0001).

DATA CONCLUSION

DWI and DCE-MRI and derived variables were significantly helpful in discriminating benign and malignant soft-tissue tumors complementary to conventional MRI.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:798-809.

Does fluid collection impact radiotherapy outcomes after wide excision of lower extremity soft tissue sarcoma?

Background

Fluid collection (FC) of lymph or blood may accumulate at the site of excision after surgery for soft tissue sarcoma, with reported incidence rates from 10% to 36%. The purpose of this study is to analyze the impact of FC on local recurrence (LR) and wound complication rates after adjuvant postoperative radiotherapy (PORT) in lower extremity soft tissue sarcoma (LE-STS).

Methods

Eighty-eight patients diagnosed with LE-STS were curatively treated with wide excision and PORT. FC developed in 51.1% of patients. Full FC volumes were included in the irradiation field throughout the full course of PORT for 36 patients (80.0%). A median of 61.2 and 63 Gy was prescribed for patients with and without FC, respectively.

Results

After a median follow-up of 4.3 years, patients with and without FC had 5-year local control rates of 77.7% and 90.8% (P = 0.105). Eight patients with FC had LR, of which six patients had recurrent tumors at or within 4 cm of the FC wall and three of these patients had out-of-field LR. Wound complication occurred after RT in 3 (6.7%) of 45 patients with FC and 1 (2.3%) of 43 patients without FC.

Conclusions

FC presents a potential risk for increased LR, particularly near the FC wall. Based on reasonable wound complication rates, we suggest the need and feasibility of fully including FC volumes in the irradiation field.

Detection of soft-tissue abscess: Comparison of diffusion-weighted imaging to contrast-enhanced MRI

PURPOSE

To compare the diagnostic performances of diffusion-weighted imaging (DWI)-combined magnetic resonance imaging (MRI) performed without intravenous contrast material with gadolinium contrast material-enhanced (CE) MRI for diagnosing soft-tissue abscesses.

MATERIALS AND METHODS

In all, 119 patients (mean age: 56 years) with skin and soft-tissue infection who underwent contrast-enhanced MRI with DWI (b = 0-800) were included. Two readers independently reviewed both image sets-nonenhanced conventional MR images (NECI)+DWI, and NECI+contrast enhanced fat-suppressed T₁ -weighted imaging (CEFST₁ )-for the presence of abscess. To compare the diagnostic performance for diagnosing abscess between NECI+DWI, and NECI+CEFST₁ , McNemar tests for sensitivity and specificity, and areas under the receiver-operating characteristic curves (AUC) analyses, were performed. Interobserver agreements (κ) were calculated for each image set.

RESULTS

Forty of 119 patients were confirmed with abscess. Sensitivity and specificity were 90.0% and 88.6% for NECI+DWI, and 82.5% and 89.9% for NECI+CEFST₁ in reader 1, whereas 77.5% and 88.6% for NECI+DWI, and 80.0% and 84.8% for NECI+CEFST₁ in reader 2, respectively. There was no significant difference in sensitivities and specificities between NECI+DWI and NECI+CEFST₁ (reader 1: P = 0.453, P = 0.999, reader 2: P = 0.999, P = 0.453, respectively). Likewise, AUC analyses demonstrated no significant difference between NECI+DWI and NECI+CEFST₁ (P = 0.53 in reader 1, P = 0.97 in reader 2). Interobserver agreement between the two readers was substantial in both image sets: 0.80 (NECI+DWI), and 0.76 (NECI+CEFST₁ ).

CONCLUSION

Noncontrast-enhanced MRI with DWI has comparable diagnostic performance to contrast-enhanced MRI for diagnosing soft-tissue abscesses.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:60-68.

Clinical relevance of the apparent diffusion coefficient value of metastatic bone tumours on diffusion-weighted MRI images: differences according to the types of primary tumour, the affected bones, and clinical factors

AIM

To evaluate whether the apparent diffusion coefficient (ADC) of metastatic bone tumours on diffusion-weighted magnetic resonance imaging (MRI) images differs according to the type of primary cancer, the affected bone, and clinical factors.

MATERIALS AND METHODS

For this retrospective study, two radiologists reviewed MRI images, including ADC maps, of 67 patients (M:F=38:29; median age, 48 years) who were diagnosed with bone metastasis by means of histological or clinical confirmation. The primary tumours included 29 lung adenocarcinomas, 15 invasive ductal adenocarcinomas of the breast, 13 hepatocellular carcinomas, six prostatic carcinomas, and four renal cell carcinomas. ADC values of the metastatic tumour were compared according to the type of primary malignancy, the affected bone, and the age and sex of the patient using Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction. In addition, pre-contrast CT images were available in 38 of 67 patients; a subanalysis of the CT radiodensity and ADC values were performed with Spearman correlation.

RESULTS

The mean, standard deviation, and minimum and maximum values of the ADC of metastatic bone tumours did not differ significantly according to type of primary malignancy, the affected bone, or clinical variables (p>0.1). The ADC value was not significantly correlated with CT radiodensity (p=0.24). Intra- and interobserver agreements for the mean ADC values were excellent (intra-observer: p=0.98; interobserver: p=0.98).

CONCLUSIONS

Assessment of the ADC value of metastatic bone tumours is not reliable for differentiation of the type of primary cancer.

MRI of lesser metatarsophalangeal joint plantar plate tears and associated adjacent interspace lesions

OBJECTIVE

To identify the variety of second and third intermetatarsal space (IS) lesions that may coexist with and without adjacent metatarsophalangeal joint (MTP) plantar plate (PP) tears.

MATERIALS AND METHODS

One hundred forefoot MRIs in 96 patients with metatarsalgia obtained between 30 September 2011 and 21 July 2012 using 1.5- or 3-T MRI were retrospectively reviewed in consensus by two MSK radiologists and one podiatrist (DPM). MRI was evaluated for second and third MTP PP tear and the presence/nature of second and third IS lesions. Second and third IS neuromas were measured in transverse (trans) dimension.

RESULTS

A total of 40 PP tears were identified: 36 at the second and 4 at the third MTP. Second MTP PP tear was identified in 33% of females and 40.5% of males. In the 63 female feet there were 21 second MTP PP tears, all of which also had second IS lesions: pericapsular fibrosis (16), bursitis (4), and ganglion (1). In the 37 male feet there were 15 second MTP PP tears, 14 of which had second IS lesions: pericapsular fibrosis (8), bursitis (5), and ganglion (1). There was no definite second IS neuroma adjacent to any second MTP PP tear. In females without PP tear, there were 24 second (3 mm trans average) and 43 third IS neuromas (4.1 mm trans average). In males without PP tear, there were 9 second (3.4 mm trans average) and 16 third IS neuromas (4.1 mm trans average).

CONCLUSIONS

MTP PP tears occurred in 40% of our cases, 90% of which occurred at the second MTP. Almost all coexisted with non-neuromatous second IS lesions.

Myxoid liposarcoma of the spermatic cord: US and MR imaging findings

We report a patient with myxoid liposarcoma of the spermatic cord in whom combined use of both ultrasound (US) and MRI helped to suggest the diagnosis. The lesion was solid at US and vascularized at color Doppler. T1-weighted MRI did not show fat within it; on T2-weighted images it had high signal intensity, with a cyst-like appearance. It is known that fat-poor myxoid liposarcomas with high water content may mimic a cystic lesion on non-contrast-enhanced MR; then, a combination of MRI findings, suggesting a cyst, and of US findings, showing the mass was actually solid and vascularized, allowed preoperatively the diagnosis of fat-poor myxoid liposarcoma.

Imaging evaluation of musculoskeletal tumors

In this chapter, we review different imaging modalities, including radiography, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and nuclear medicine scintigraphy, and their application to musculoskeletal neoplasm. Advantages and limitations of each modality are reviewed, and suggestions for imaging approach are provided.

"Cystic"-appearing soft tissue masses: what is the role of anatomic, functional, and metabolic MR imaging techniques in their characterization?

Although conventional MR imaging with contrast-enhanced T1-weighted sequences is of paramount importance for evaluating soft tissue masses, noncontrast MR sequences have emerged that facilitate their characterization. In this article, the utility and pitfalls of conventional MR imaging with T1-weighted, fluid-sensitive, and contrast-enhanced sequences will be discussed, along with that of functional (diffusion weighted imaging) and metabolic (proton MR spectroscopy) non-contrast-enhanced techniques for the purpose of soft tissue mass characterization. In particular, we discuss the application of these techniques to differentiating neoplastic or inflammatory masses that have high fluid content from benign cysts, as this distinction is a common pitfall of conventional sequences.

Musculoskeletal tumors: how to use anatomic, functional, and metabolic MR techniques

Although the function of magnetic resonance (MR) imaging in the evaluation of musculoskeletal tumors has traditionally been to help identify the extent of disease prior to treatment, its role continues to evolve as new techniques emerge. Conventional pulse sequences remain heavily used and useful, but with the advent of chemical shift imaging, diffusion-weighted imaging, perfusion imaging and MR spectroscopy, additional quantitative metrics have become available that may help expand the role of MR imaging to include detection, characterization, and reliable assessment of treatment response. This review discusses a multiparametric approach to the evaluation of musculoskeletal tumors, with a focus on the utility and potential added value of various pulse sequences in helping establish a diagnosis, assess pretreatment extent, and evaluate a tumor in the posttreatment setting for recurrence and treatment response.

Malignant soft tissue tumors of the biceps muscle mistaken for proximal biceps tendon rupture

Tears of the proximal long head of the biceps tendon are among the most common tendon tears in the body. In most cases, the diagnosis is easily determined based on the history and physical examination. However, malignant soft tissue tumors can simulate proximal biceps tendon tears. Although tumors simulating tears of the distal biceps tendon at the elbow have been reported, to the authors' knowledge, no previous cases of tumors simulating or being mistaken for proximal biceps tendon tears have been reported.This article describes 2 cases of malignant sarcomas initially mistaken for tears of the long head of the biceps tendon. In the first case, a 62-year-old woman developed swelling in her arm after feeling a twinge in her shoulder. A magnetic resonance imaging scan was misread as a biceps tendon tear and not treated by the examining physician. In the second case, a mass appeared with little trauma in the brachium of a 70-year-old man. On physical examination, the mass was hard to palpation. In each case, biopsy revealed a soft tissue sarcoma. Both patients underwent wide excision with radiation and are currently disease free. These 2 cases emphasize the importance of obtaining a good history and of performing a thorough shoulder and arm examination in patients with deformities consistent with tears of the long head of the biceps tendon.

Pediatric soft tissue sarcomas

After a brief discussion of the rarity of soft tissue sarcomas in children and of the limited ability of magnetic resonance imaging to provide a tissue diagnosis, this article discusses the incidence, presentation, treatment, prognosis, and imaging characteristics of the more common and unusual pediatric soft tissue sarcomas. It begins with extensive discussion of rhabdomyosarcoma, synovial sarcoma, and congenital/infantile fibrosarcoma. It then presents a more abbreviated discussion of uncommon tumors such as alveolar soft part sarcoma, epithelioid sarcoma, extraosseous Ewing's sarcoma, granulocytic sarcoma, hemangiopericytoma, liposarcoma, malignant fibrous histiocytoma, malignant peripheral nerve sheath tumor, and undifferentiated sarcoma.

Differences in sonographic features of ruptured and unruptured epidermal cysts

OBJECTIVES

This study aimed to report the differences in sonographic features of ruptured and unruptured epidermal cysts.

METHODS

We reviewed and analyzed the sonographic features of superficial epidermal cysts of in 2 subgroups of 46 patients: 20 with ruptured cysts and 26 with unruptured cysts. All lesions were diagnosed either by excisional biopsy or by debridement biopsy. Sonographic features used in the analysis included tumor size, location, echo texture, pericystic changes, boundary, and shape on gray scale sonography and lesion vascularity on color Doppler sonography. Pathologic examinations were reviewed with emphasis on differences between ruptured and unruptured epidermal cysts.

RESULTS

Unruptured epidermal cysts showed significantly higher frequencies of an oval shape, presence of a halo, well-circumscribed boundaries, and lack of blood flow signals (P < .05). In contrast, ruptured cysts usually had a lobulated shape, a slightly poorly defined or poorly defined boundary, the absence of a halo, and intermediate grades of lesion vascularity. The lesion sizes and sonographic features, including dermal attachment, a hypoechoic echo texture, posterior acoustic enhancement, and the presence of intralesional hyperechoic strips and hypoechoic debris, showed no significant differences between the groups (P > .05). In pathologic studies, acute and chronic inflammatory reactions, more prominent microvessels, and abscess formation in the adjacent stromal tissue, the lesions, or both could be detected in the 20 ruptured epidermal cysts but not in the unruptured cysts.

CONCLUSIONS

This research shows that recognition of different sonographic features is helpful for differentiating ruptured and unruptured epidermal cysts.

Epidermal cysts in the superficial soft tissue: sonographic features with an emphasis on the pseudotestis pattern

OBJECTIVES

The purposes of this study were to report the sonographic features of superficial epidermal cysts with an emphasis on the characteristic pseudotestis appearance and to highlight the spectrum of ancillary findings.

METHODS

The medical records and sonographic studies of all cases of surgically proven epidermal cysts (n = 42) from January 2005 through December 2009 were reviewed. Twenty-six epidermal cysts (62%) that appeared on sonography as ovoid nodules with homogeneous low to medium echoes, simulating a testicle, were included in the pseudotestis group. The other 16 epidermal cysts (38%) without the pseudotestis pattern were included in the nonpseudotestis group. The age, sex, lesion size, length to width ratio, sonographic appearances, and frequencies of rupture and infection were compared between the groups.

RESULTS

Epidermal cysts in the nonpseudotestis group presented as heterogeneously echoic or lobulated nodules or had a concentric ring or target appearance. There were no significant differences in the age, sex, lesion size, and length to width ratio between the groups. The pseudotestis group had significantly higher frequencies of intralesional bright echogenic reflectors and filiform anechoic areas than the nonpseudotestis group (P < .01). There were no significant differences in the associated ancillary sonographic features, including posterior acoustic enhancement, dermal attachment, focal dermal protrusion, and frequencies of rupture and infection between the groups.

CONCLUSIONS

In this study, two-thirds of the superficial epidermal cysts had a characteristic pseudotestis pattern on sonography, whereas the others could be suspected by recognition of the ancillary sonographic findings, including dermal attachment and focal dermal protrusion or a distinctive concentric ring or target pattern.

Soft-tissue tumors and tumorlike lesions: a systematic imaging approach

Soft-tissue lesions are frequently encountered by radiologists in everyday clinical practice. Characterization of these soft-tissue lesions remains problematic, despite advances in imaging. By systematically using clinical history, lesion location, mineralization on radiographs, and signal intensity characteristics on magnetic resonance images, one can (a) determine the diagnosis for the subset of determinate lesions that have characteristic clinical and imaging features and (b) narrow the differential diagnosis for lesions that demonstrate indeterminate characteristics. If a lesion cannot be characterized as a benign entity, the lesion should be reported as indeterminate, and the patient should undergo biopsy to exclude malignancy.

MR imaging of urgent inflammatory and infectious conditions affecting the soft tissues of the musculoskeletal system

Soft tissue infections and inflammatory conditions of the musculoskeletal system are a group of disorders commonly seen by emergency room physicians and radiologists. Many of these entities can either be limb- or life-threatening. Magnetic resonance imaging is currently the best imaging modality to evaluate these conditions. In this review, the characteristic imaging findings of cellulitis, abscess formation, necrotizing fasciitis, pyomyositis, diabetic ischemic infarction, acute and exertional compartment syndromes, and rhabdomyolysis will be emphasized as well as imaging factors that can help to differentiate these disorders.

Post-operative imaging of soft tissue sarcomas

Soft tissue sarcomas are uncommon malignancies that have a high risk of local recurrence despite adequate initial surgery. The aim of follow-up imaging with any malignancy is to detect recurrence promptly so that treatment can be instigated at the earliest possible opportunity. In this review article, we discuss the imaging modalities that can be employed to detect local recurrence following surgery for an extremity soft tissue sarcoma. The role of radiographs, computed tomography, magnetic resonance imaging and positron emission tomography is reviewed followed by a discussion on the imaging modalities useful in the detection of metastatic disease. Finally, we present a robust pathway that is suggested for the follow-up of patients with an extremity soft tissue sarcoma.

Soft-tissue tumors evaluated by line-scan diffusion-weighted imaging: influence of myxoid matrix on the apparent diffusion coefficient

PURPOSE

To compare the apparent diffusion coefficients (ADCs) of myxoid and nonmyxoid soft-tissue tumors using line-scan diffusion-weighted imaging (LSDWI), and to investigate the myxoid matrix influence on ADCs of soft-tissue tumors.

MATERIALS AND METHODS

This study enrolled 44 patients with soft tissue tumors. They were divided into two groups: one with myxoid-containing soft-tissue tumors (N = 23) and the other with nonmyxoid soft-tissue tumors (N = 21). The 44 patients were also classified histologically into 26 with malignant soft-tissue tumors and 18 with benign soft-tissue tumors. LSDWI was performed using b values of 5 and 1000 second/mm(2). The ADCs of the tumors were calculated and compared for myxoid and nonmyxoid tumors and for benign and malignant tumors.

RESULTS

The ADC (mean +/- SD) was 1.92 +/- 0.41 x 10(-3) mm(2)/second in myxoid containing tumors, whereas the ADC was 0.97 +/- 0.33 x 10(-3) mm(2)/second in nonmyxoid tumors. The ADCs of the myxoid and nonmyxoid tumors were significantly different (P < 0.01). The ADCs were 1.45 +/- 0.59 x 10(-3) mm(2)/second in malignant tumors and 1.50 +/- 0.64 x 10(-3) mm(2)/second in benign tumors. The ADCs of benign and malignant soft-tissue tumors were not significantly different.

CONCLUSION

The ADCs of myxoid-containing soft-tissue tumors were significantly higher than those of nonmyxoid soft-tissue tumors. The myxoid matrix influences ADCs of both benign and malignant soft-tissue tumors.

Soft tissue masses with “cyst-like” appearance on MR imaging: distinction of benign and malignant lesions

The purpose of this study was to assess the reliability of MR imaging features in distinguishing between benign and malignant soft tissue masses that have a "cyst-like" appearance (hypointense to muscle on T1-weighted and hyperintense on T2-weighted or fluid-sensitive MR sequences). MR imaging features of 40 patients with histologically proven soft tissue masses (27 benign and 13 malignant lesions) that were hypointense to muscle on T1-weighted and hyperintense on T2-weighted or fluid-sensitive MR sequences were analysed to see if a distinction could be made between benign and malignant lesions. There were 23 females and 17 males (mean age, 56 years; age range, 23-82 years). MR imaging features analysed for statistical significance included lesion size, lesion homogeneity, presence of lobulation, depth in relation to fascia and border definition. Clinical assessment included the age and sex of the patient and location of the lesion. Statistically significant MR imaging features favouring a diagnosis of a malignant lesion included larger average dimension of the mass (P < or = 0.004), larger greatest dimension of the mass (P < or = 0.028) and heterogeneity of the lesion on T1-weighted sequences (P = 0.017). The most statistically significant predictor of malignancy was the larger average dimension of the mass.

Chondroid lipoma of the trunk: MRI appearance and pathologic correlation

Chondroid lipoma is a rare tumour of adipose tissue, bearing a strikingly close pathologic resemblance to myxoid liposarcoma and extraskeletal myxoid chondrosarcoma. Unlike these malignant tumours, chondroid lipoma has a non-aggressive behaviour and does not require radical treatment. Although repeatedly reported in the proximal extremities and limb girdles, this rare entity may less frequently be observed in the trunk. We describe the imaging findings of a chondroid lipoma in the trunk and provide a discussion on the radiologic-pathologic correlation and differential diagnosis.

Soft-Tissue Tumors: Value of Static and Dynamic Gadopentetate Dimeglumine–enhanced MR Imaging in Prediction of Malignancy

PURPOSE

To prospectively evaluate static and dynamic gadopentetate dimeglumine-enhanced magnetic resonance (MR) imaging relative to nonenhanced MR imaging in differentiation of benign from malignant soft-tissue lesions and to evaluate which MR imaging parameters are most predictive of malignancy, with associated interobserver variability.

MATERIALS AND METHODS

One hundred forty consecutive patients (78 male patients [median age, 51 years], 62 female patients [median age, 53 years]) with a soft-tissue mass underwent nonenhanced static and dynamic contrast material-enhanced MR imaging. Diagnosis was based on histologic findings in surgical specimens (86 of 140), findings at core-needle biopsy (43 of 140), or results of all imaging procedures with clinical follow-up (11 of 140). Multivariate logistic regression analysis was used to identify the best combination of MR imaging parameters that might be predictive of malignancy. Subjective overall performance of two observers was evaluated with receiver operating characteristic analysis.

RESULTS

For subjective overall diagnosis, area under the receiver operating characteristic curve, a measure for diagnostic accuracy, was significantly larger for combined nonenhanced and contrast-enhanced MR imaging than it was for nonenhanced MR imaging alone, with no significant difference between observers. Multivariate analysis of all lesions revealed that combined nonenhanced static and dynamic contrast-enhanced MR imaging parameters were significantly superior to nonenhanced MR imaging parameters alone and to nonenhanced MR imaging parameters combined with static contrast-enhanced MR imaging parameters in prediction of malignancy. The most discriminating parameters were presence of liquefaction, start of dynamic enhancement (time interval between start of arterial and tumor enhancement), and lesion size (diameter). Results for extremity lesions were the same, with one exception: With dynamic contrast-enhanced MR imaging parameters, diagnostic performance of one observer did not improve.

CONCLUSION

Static and dynamic contrast-enhanced MR imaging, when added to nonenhanced MR imaging, improved differentiation between benign and malignant soft-tissue lesions.

The MR imaging appearances and natural history of seromas following excision of soft tissue tumours

Fluid collections (seromas) may accumulate at the site of surgery following excision of musculoskeletal soft tissue tumours. The aim of this retrospective study was to review the magnetic resonance (MR) imaging features of postoperative seromas identifying changes over time on follow-up scans. A total of 170 MR scans from 80 patients were reviewed showing one or more seromas. All patients had undergone previous surgery for a musculoskeletal soft tissue tumour. The typical MR appearances of a seroma were shown to be a well-defined oval or rounded (54%) soft tissue mass, arising at the site of previous surgery, with a thin, dark pseudocapsule, surrounding soft tissue oedema (80%), homogeneous contents that are hypointense (relative to adjacent muscle) on T1-weighted images (74%) and hyperintense on T2-weighted and STIR images (79%). Approximately one-quarter of cases revealed atypical features including hyperintense contents on T1-weighted (26%) and/or heterogeneous contents on T2-weighted images (21%), reflecting the breakdown of blood products and organization of the fluid collection. A distinctive fine feathery pattern arising from the inner surface of the seroma or from septations was identified in 10% of cases. In those patients who underwent one or more follow-up scans, the volume of the seromas decreased in 66% cases, remained unchanged in 15% and increased in 19%. Seromas are not an uncommon finding (<10% of cases) following surgery for a soft tissue tumour. The majority of cases show the typical MR features of a fluid collection. The pitfalls in differentiating an atypical seroma from a recurrent soft tissue sarcoma are discussed.

The MRI features and treatment of scapulothoracic bursitis: report of four cases

Among cases of soft tissue tumours arising between the inferior angle of the scapula and thoracic wall, scapulothoracic bursitis has rarely been reported. All the reported cases were surgically treated and there have been no reports about the results of conservative treatment observed for a long period. Therefore, we retrospectively evaluated the clinical findings, magnetic resonance imaging (MRI) features, and treatment procedures in order to elucidate the differential diagnosis for, and efficacy of, conservative treatment. The patients were those who consulted our department of orthopedic surgery from 1994 to 1998 with complaints of thoracic back tumours. The patients were 2 men and 2 women whose ages ranged from 46 to 66 years. The tumour locations, MRI findings and treatments were evaluated. The cysts appeared in the inferior angle of the scapula with the shoulder flexed and adducted. There was neither pain nor tenderness, local heat nor redness. The cysts were elastic hard, fluctuating, and less mobile and the margins were well circumscribed by palpation. The diameters were from 6 x 6 cm to 20 x 15 cm. On MR imaging, the cysts were located between the serratus anterior muscle and the chest wall. Slightly high signal intensity on T1WI, high on T2WI and fluid-fluid levels were seen in the cysts in three cases. For the treatment, in one case we performed multiple aspirations until a reduction appeared to occur. The average aspirated contents of the cyst were 100 mL to 200 mL and were bloody-serous. In two cases no special treatments were employed, and in one case the tumour was surgically removed because it was unresponsive to aspiration. In the three cases with conservative treatment, the follow-up time was 8, 9 and 25 months, respectively. The tumours had disappeared in all cases at the time of the final follow-up. High signal intensities on T1 and T2 weighted images, and fluid-fluid level on T2 weighted images were very useful MRI features for the diagnosis of scapulothoracic bursitis. Our observations indicate that conservative treatment can be successful and surgery is not necessary except for cases with pain, excessive friction, or dysfunction.

Sonography of ankle Ganglia with pathologic correlation in 10 pediatric and adult patients

OBJECTIVE

We describe the sonographic imaging characteristics of ankle ganglia with pathologic correlation in 10 patients.

CONCLUSION

Foot and ankle ganglia exhibit a spectrum of sonographic appearances from round and completely anechoic masses to hypoechoic, multilobulated, multiseptated masses with dependent debris. All the ganglionic cysts examined in our study showed posterior acoustic enhancement without solid nodules on sonography.

Forefoot pain involving the metatarsal region: differential diagnosis with MR imaging

Many disorders produce discomfort in the metatarsal region of the forefoot. These disorders include traumatic lesions of the soft tissues and bones (eg, turf toe, plantar plate disruption, sesamoiditis, stress fracture, stress response), Freiberg infraction, infection, arthritis, tendon disorders (eg, tendinosis, tenosynovitis, tendon rupture), nonneoplastic soft-tissue masses (eg, ganglia, bursitis, granuloma, Morton neuroma), and, less frequently, soft-tissue and bone neoplasms. Prior to the advent of magnetic resonance (MR) imaging, many of these disorders were not diagnosed noninvasively, and radiologic involvement in the evaluation of affected patients was limited. However, MR imaging has proved useful in detecting the numerous soft-tissue and early bone and joint processes that occur in this portion of the foot but are not depicted or as well characterized with other imaging modalities. Frequently, MR imaging allows a specific diagnosis based on the location, signal intensity characteristics, and morphologic features of the abnormality. Consequently, MR imaging is increasingly being used to evaluate patients with forefoot complaints. Radiologists should be familiar with the differential diagnosis and MR imaging features of disorders that can produce discomfort in this region.

Relationship between sonographic and pathologic findings in epidermal inclusion cysts

PURPOSE

We evaluated the sonographic findings in epidermal inclusion cysts and related them to the pathologic findings.

METHODS

We retrospectively reviewed the sonograms and pathology specimens of 24 patients with pathologically proven epidermal inclusion cysts. We evaluated the lesions for shape, size, internal echogenicity, posterior sound enhancement, and presence of color Doppler signals. We classified the masses into 5 sonographic types according to their internal echogenicity. The relationship between the sonographic types and the pathologic findings was examined.

RESULTS

The masses were ovoid or spherical in 17 cases (71%), lobulated in 5 (21%), and tubular in 2 (8%). The longest diameter ranged from 1 to 6 cm (mean, 3.1 cm). Twenty-three cases (96%) were associated with posterior sound enhancement. Color Doppler signals were absent in 20 cases, but some vascularity was noted in 4 ruptured epidermal cysts, in areas of granulation tissue. The most common sonographic type was a hypoechoic lesion with scattered echogenic reflectors (10 cases). Sonographic findings were related to the lamellation of keratin debris and the granulation tissue secondary to rupture. Most cases with a lobulated configuration (4 of 5) or color Doppler signals (4 of 4) were ruptured cysts.

CONCLUSIONS

Epidermal inclusion cysts most often appeared sonographically as a hypoechoic mass containing variable echogenic foci without color Doppler signals. Ruptured epidermal cysts, however, may have lobulated contours and show color Doppler signals, mimicking a solid mass.

Magnetic resonance imaging of musculoskeletal soft tissue masses

The role of MR imaging in the evaluation of children with large, deep, or infiltrative soft tissue masses is to characterize and determine the extent of the lesion for treatment planning. There are a small number of soft tissue tumors with MR imaging appearances characteristic enough to allow a specific diagnosis, obviating biopsy. In the remaining cases with nonspecific imaging appearances, MR imaging is used for anatomic staging, but tissue sampling is still required for determining histology and grading.

MR imaging of bone oedema: mechanisms and interpretation

Widespread use of MRI now allows the routine identification of previously unevaluated traumatic bone marrow oedema and haemorrhage. Similar marrow oedema is identified in patients with tumours, hyperaemia and medullary congestion. Patterns and extent of traumatic bone marrow oedema and haemorrhage are dictated by mechanism. Diffusion techniques may allow precise evaluation of severity of injury. Illustrative examples and discussion are presented. Eustace, S. (2001). Clinical Radiology56, 4-12.

Myxoid liposarcoma: appearance at MR imaging with histologic correlation

Although myxoid liposarcoma is a subtype of liposarcoma, it may be difficult to establish the correct diagnosis with magnetic resonance (MR) imaging due to the lack of fat signal intensity. Without the administration of gadolinium contrast material, the tumor may even mimic a cystic tumor. A spectrum of MR imaging abnormalities occur in myxoid liposarcoma, depending on the amount of fat and myxoid material, the degree of cellularity and vascularity, and the presence of necrosis. Most myxoid liposarcomas have lacy or linear, amorphous foci of fat. Some myxoid liposarcomas appear to be cystic at nonenhanced MR imaging, although they enhance like other solid masses at contrast material-enhanced MR imaging. The enhancing areas within the tumor represent increased cellularity and vascularity; the nonenhancing areas represent necrosis, reduced cellularity, and accumulated mucinous material. Gadolinium-enhanced imaging is important in differentiating myxoid liposarcoma from benign cystic tumors. Characterization of the tumor with MR imaging plays an important role in the management of myxoid liposarcoma.

Tissue characterization in the female pelvis by means of MR imaging

Pelvic imaging techniques such as computed tomography and ultrasonography provide a limited capability for tissue characterization. Fat, fluid, and calcification, for example, can be identified on the basis of parameters such as x-ray attenuation, echogenicity, and sound attenuation. Because of the many tissue parameters, such as T1, T2, magnetic susceptibility, and chemical shift, that contribute to signal intensity, magnetic resonance (MR) imaging may afford an ability to identify a wider array of specific tissues. The purpose of this article is to review the ability of MR imaging to help identify various types of soft tissue and to provide an approach to interpretation of MR images of the female pelvis through tissue characterization. Lipid, fluid, hemorrhage, smooth muscle, fibrosis, solid malignant tissue, and hydrated soft tissue (including edema, mucin, and myxomatous tissue) have typical MR imaging properties, and their presence in a mass can often be established on MR images. Consideration of the tissue composition of various pathologic processes in the pelvis can result in more systematic approaches to image interpretation and thus narrow the differential diagnosis.

Magnetic resonance imaging of musculoskeletal tumors: skeletal and soft tissue masses

The purpose of this article is to review the MRI characteristics of musculoskeletal tumors, including skeletal and soft tissue masses. MRI has become the premier imaging modality for the evaluation of musculoskeletal tumors because of its excellent soft tissue contrast, its sensitivity to bone marrow and soft tissue edema, and its multiple imaging planes. In a substantial subset of cases, MRI can provide a diagnosis or a short differential diagnosis, while certain tumors have no distinguishing signal characteristics. MRI of musculoskeletal tumors can also be challenging, because the MRI appearance of certain lesions can be misleading, and a knowledge of the instances in which MRI over- and underestimates the malignancy of lesions is invaluable. The importance of correct protocols for tumor evaluation, both in diagnosis and in pre-operative evaluation, are discussed. Common pitfalls that may over- or underestimate the aggresivity of lesions will be highlighted, as will the role of gadolinium enhancement in the evaluation of lesions. The MRI appearance of common benign and malignant muculoskeletal lesions will be illustrated.