Non-neoplastic conditions presenting as soft-tissue tumours

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 1: tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous-organ soft tissues, as well as the peripheral and autonomic nervous system.

The safety of primary surgical excision of small deep indeterminate musculoskeletal soft tissue masses

OBJECTIVE

To determine the suitability of primary excision of small indeterminate deep soft tissue masses presenting to a tertiary musculoskeletal oncology service.

METHODS AND MATERIALS

Review of all patients referred to a specialist musculoskeletal oncology service over a 20-month period with a deep indeterminate soft tissue mass by non-contrast MRI criteria that was recommended for primary surgical excision due to relatively small size (<30 mm). Data collected included age, gender, site and maximal size of the lesion, and final histological diagnosis for excised lesions.

RESULTS

85 patients were included, mean lesion size being 12 mm (range 5-29 mm). Primary surgical resection had been undertaken in 69 cases (81.2%) by the conclusion of data collection, 36 males and 33 females with mean age of 45.6 years (range 11-80 years). Of these, 11 cases (15.9%) were non-neoplastic, 53 (76.8%) were benign, 1 (1.4%) was intermediate grade, while 4 (5.8%) were malignant including 3 synovial sarcomas. Two of these were treated with re-excision of the tumour bed showing no residual disease, with no evidence of local recurrence at a mean of 10.7 months post-excision.

CONCLUSION

Primary surgical excision of small deep soft tissue masses that are indeterminate by non-contrast MRI criteria is considered a safe procedure when undertaken in a specialist musculoskeletal oncology service, with only 4 of 69 cases (5.8%) being malignant.

ADVANCES IN KNOWLEDGE

Small indeterminate deep soft tissue masses can safely be treated with primary excision in the setting of a specialist musculoskeletal oncology service.

Non-neoplastic Soft Tissue Tumors and Tumor-like Lesions

Clinicians are commonly faced with patients presenting with a solitary palpable soft tissue mass. Most soft tissue lesions are benign, and not every mass is due to a neoplastic process. Many pathologies can mimic a malignant tumor. Despite appropriate clinicoradiologic assessment, these lesions can be mistaken for a soft tissue sarcoma and can lead to multiple investigations or an intervention, inconveniencing patients and leading to an increased health care cost. With the relevant clinical history, clinical examination, and specific imaging characteristics, the diagnosis can be narrowed. We present a pictorial review of soft tissue sarcoma mimics with guidance on appropriate differential diagnoses.

CT imaging features of skeletal muscle metastasis: A rare tumour group with different patterns

INTRODUCTION

Skeletal muscle metastasis (SMM) are rare and can have different patterns on computed tomography (CT). Our aim was to estimate the frequency of the different patterns, primary tumours and localizations of SMM in a large single-centre sample.

METHODS

A retrospective search in the database of our radiological institution was performed for patients with SMM. The primary tumour, affected muscles and CT patterns were estimated.

RESULTS

Overall, 104 SMM were diagnosed in 82 patients. In 11 patients (13.4%), SMM were the isolated manifestation of metastatic disease in clinical work up. Regarding primary tumours, gastrointestinal tumours (24.4%), lung cancer (20.4%) and malignant melanoma (13.4%) were identified most frequently. Other malignancies were rare. Most commonly, the trunk musculature was affected (41.3% of the cases). SMM type 1 were identified in 37 cases (35.6%), type 2 in 64 cases (61.5%), type 3 in 2 cases (1.9%) and type 4 in one case (1%).

CONCLUSIONS

The present study shows typical imaging appearances of SMM based on a large patient sample in a single centre. SMM has a rare occurrence with several different patterns, which can impose diagnostic difficulties and varies possible differential diagnoses.

Diagnostic utility of perilesional muscle edema in myositis ossificans

OBJECTIVES

To investigate the value of extensive perilesional muscle edema for the differentiation between myositis ossificans (MO) and malignant intramuscular soft tissue tumors on MRI.

MATERIALS AND METHODS

Two blinded readers analyzed MR examinations of 90 consecutive patients with intramuscular soft tissue masses (group 1: MO, n = 20; group 2: malignant tumors, n = 70). Extent of edema around lesions was graded (0, none; 1, minimal edema; 2, moderate edema; 3, extensive edema). Edema-lesion ratio (ELR = ratio of the maximal diameter of the edema and the maximal diameter of the central lesion) was calculated. ROC analysis, Mann-Whitney U test, and Kappa test were used.

RESULTS

A total of 70% and 60% of patients with MO had edema grade 3 (reader 1/reader 2), 30%/40% edema grade 2. For the patients with malignant tumors, it was 2.9%/1.4% (edema grade 3) and 16%/23% (edema grade 2). Interrater reliability was substantial (kappa = 0.66). Extent of edema was significantly higher for patients of group 1 (p < 0.0001, both readers). Mean ELR was 3.60 (group 1) and 1.35 (group 2), with statistically significant differences (p < 0.0001). Grade 3 edema showed a sensitivity/specificity of 70%/97.1% (reader 1) and 60%/99% (reader 2) for diagnosing MO. For ELR > 2.0, sensitivity was 90% and specificity 91% for diagnosing MO.

CONCLUSIONS

Extensive perilesional muscle edema on MRI of more than double the size of the central lesion is highly specific, but not pathognomonic for myositis ossificans in the early/intermediate stage in the differentiation to malignant intramuscular soft tissue lesions.

Small indeterminate superficial soft tissue masses: relationship between depth and histological grade

OBJECTIVE

To determine whether the location of a small, indeterminate soft tissue mass within the subcutaneous compartment is related to its histological grade.

METHODS

All Sarcoma Service referrals over a 12 month period of small (<3 cm) superficial soft tissue masses, indeterminate by MRI evaluation which subsequently underwent primary excision biopsy were included. Lesions were categorised by their anatomical location in the subcutaneous compartment. Histopathological diagnoses were categorized according to12 WHO 2013. χ2 statistical analysis was performed to determine the relationship between lesion depth and histological grade.

RESULTS

The study included 43 patients, mean age 42 years (range 15-71 years). Within the subcutaneous compartment, 16 lesions were categorized as superficial, 9 lesions central and 18 lesions deep, of which 9 were non-neoplastic, 29 benign, 1 intermediate-grade and 4 malignant. Location in the deep aspect of the subcutaneous compartment was associated with a higher risk of intermediate or malignant histology (p = 0.02).

CONCLUSION

The location of a small, indeterminate soft tissue mass within the subcutaneous compartment may be an indicator of histological aggressiveness. Lesions in the deep subcutaneous compartment are more likely to be intermediate-grade/malignant lesions. Therefore, if considering excision biopsy as definitive treatment, a wider margin may be appropriate.

ADVANCES IN KNOWLEDGE

Small, indeterminate soft tissue masses can be aggressive and the anatomical depth within the subcutaneous tissue may be a potential indicator of histological aggressiveness.

The incidence and diagnostic relevance of chemical shift artefact in the magnetic resonance imaging characterisation of superficial soft tissue masses

OBJECTIVE

Chemical shift artefact (CSA) is often encountered during MRI evaluation of superficial soft tissue masses. The study aim was to determine the incidence and diagnostic relevance of CSA in a consecutive series of superficial soft tissue masses referred to a specialist musculoskeletal sarcoma service.

METHODS

All patients referred over a 6 month period with a non-lipomatous superficial soft tissue mass were prospectively analysed. Patients characteristics (age, gender), lesion features (anatomical location, size, relationship to the skin and deep fascia), presence of CSA and final histopathological diagnosis were collected. The presence of CSA was statistically analysed against these clinical, imaging and histopathological variables.

RESULTS

128 patients fulfilled the inclusion criteria [63 males, 65 females; mean age = 50.6 years (7-96 years)]. CSA was present in 50 cases (39.1%) overall, but in 39 (41.5%) of 94 cases with histological diagnosis. There was no statistically significant relationship to any assessed variable apart from relationship to the deep fascia, CSA being more frequent in lesions contacting the fascia compared to lesions contacting both skin and fascia (p-value 0.02). In particular, the presence of CSA did not allow differentiation between non-malignant and malignant lesions.

CONCLUSION

The presence of CSA is a not infrequent finding in the MRI assessment of superficial soft tissue masses but does not appear to be of any significance in differentiating between non-malignant and malignant lesions.

ADVANCES IN KNOWLEDGE

CSA is a relatively common finding in association with superficial soft tissue masses, but does not indicate a particular histological diagnosis or help in the differentiation of non-malignant from malignant lesions.

Ultrasound of Soft Tissue Masses and Fluid Collections

Soft tissue masses and fluid collections are frequently encountered in sonographic practice, either as principal indication for diagnostic examination or as an incidental finding during an examination performed for other indications. Sonography is a good first-line imaging modality for evaluation of superficial masses and fluid collections, but requires meticulous attention to technique to avoid diagnostic pitfalls. Although many superficial masses are diagnosed with ultrasound, there are several potential diagnostic challenges, including differentiating hematomas from sarcomas. This article provides an image-rich review of the sonographic features of common soft tissue masses, with emphasis on practical tips to accurately recognize important pathology.

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.

Surgical considerations when reporting MRI studies of soft tissue sarcoma of the limbs

Soft tissue sarcomas (STS) are rare tumours that require prompt diagnosis and treatment at a specialist centre. Magnetic resonance imaging (MRI) has become the modality of choice for identification, characterisation, biopsy planning and staging of soft tissue masses. MRI enables both the operating surgeon and patient to be optimally prepared prior to surgery for the likelihood of margin-negative resection and to anticipate possible sacrifice of adjacent structures and consequent loss of function. The aim of this review is to aid the radiologist in performing and reporting MRI studies of soft tissue sarcomas, with particular reference to the requirements of the surgical oncologist.

Small, superficial, indeterminate soft-tissue lesions as suspected sarcomas: is primary excision biopsy suitable?

OBJECTIVE

Suspected soft-tissue sarcomas are typically investigated using magnetic resonance imaging (MRI), with a view to planning image-guided core needle biopsy for confirmation of the histological diagnosis. Indeterminate superficial lesions may be small and therefore potentially difficult to biopsy safely, such lesions possibly being more amenable to primary excision biopsy. The aim of this study is to determine the suitability of this practice in the setting of a specialist sarcoma service.

MATERIALS AND METHODS

All patients referred over a 12-month period to the sarcoma service with a small (<3-cm), indeterminate, superficial soft-tissue mass according to MRI criteria, or a small lesion of the hand or foot deemed unsafe for percutaneous biopsy, and who underwent primary excision biopsy were included. The histology results were categorized into neoplastic and non-neoplastic lesions, and assessed for resection completeness.

RESULTS

Fifty-eight patients fulfilled the inclusion criteria from all patients referred to the sarcoma service in a 12-month period. Of these, 42 out of 58 (72.4%) had benign neoplasms, 4 out of 58 (6.9%) had malignant tumours, 2 out of 58 (3.4%) an intermediate grade lesion, while 10 out of 58 (17.2%) were non-neoplastic. All 4 malignant lesions were completely excised at the time of excision biopsy.

CONCLUSIONS

Primary excision biopsy of small, indeterminate soft-tissue masses within the setting of a specialist sarcoma service is a suitable management option. Only a small proportion of small superficial soft-tissue lesions with indeterminate MRI features are malignant tumours.

Skeletal muscle metastases on magnetic resonance imaging: analysis of 31 cases

Aim of the study

To investigate the magnetic resonance imaging (MRI) features of skeletal muscle metastases (SMM).

Material and methods

The records of 31 patients with proven SMM were retrospectively reviewed. Clinical history, type of primary malignancy, location of metastases, and MRI features of SMM were evaluated. Based on MRI findings, SMM were divided into three MRI types. The correlation between MRI types with ages and pathology category, between MRI types of SMM and ages, as well as MRI types of SMM and pathology category were analysed with Spearman's rho.

Results

The most common primary tumour was genital tumour (25.8%) and bronchial carcinoma (19.4%), and the most common cell type was adenocarcinoma (58.1%). SMM were located in the iliopsoas muscle (26.3%), paravertebral muscles (21.1%), and upper extremity muscles (18.4%). MRI features: (1) Type-I localised lesions (12.90%), round-like mass limited to local regions with heterogeneous iso-signal intensity in T1WI and heterogeneous hyper-intensity in T2WI; (2) Type-II diffuse lesions without bone destruction (35.48%), abnormal diffuse swelling of the muscle with irregular boundaries and slightly hypo- to iso-intensity in T1WI and hyper-intensity in T2WI; and (3) Type-III diffuse lesions with bone destruction (51.61%), distinct irregular lump with iso-intensity in T1WI and heterogeneous hyper-intensity in T2WI with adjacent bone invasion. There was positive correlation between MRI types and ages (r = 0.431, p < 0.05). There were no significant differences of MRI types with pathology category (p > 0.05).

Conclusions

SMM features on MRI can be broadly used to classify lesions, which is beneficial for SMM diagnosis.

[Granulomatous inflammation in the bed of resected cerebral cavernoma in a child, caused by a hemostatic agent]

OBJECTIVE

The study presents a clinical observation of foreign body granuloma, which is rare productive inflammation, developed on treatment with a hemostatic material upon removal of cerebral cavernoma.

MATERIAL AND METHODS

A 4-year-old boy operated on for left parietal lobe cavernoma was diagnosed with a mass lesion during a follow-up MRI examination 4 months after surgery. The patient was re-operated in connection with suspected abscess formation. The pathological tissue was subjected to the histological and immunohistochemical examination.

RESULTS

Inflammation was accompanied by the formation of foreign body granulomas, and, in some areas, had immune nature with signs of focal destructive vasculitis, delayed maturation of the granulation tissue, and disturbance of the current organization and encapsulation processes. It is worth noting that granulomatous inflammation around a hemostatic material in the brain has no specific features during introscopy and mimics an abscess or tumor recurrence.

CONCLUSION

The use of hemostatic materials upon resection of cerebral cavernous malformations may cause formation of granuloma mimicking disease relapse or abscess in the long term period. To prevent granulomatous inflammation, removal of a hemostatic material, if possible, from the surgical field is recommended when reliable hemostasis is achieved.

Myositis ossificans circumscripta, secondary to high-velocity gunshot and fragment wound that causes sciatica

This report concerns an unusual cause of sciatica. The case presented is of a young man with myositis ossificans that resulted in sciatica and was treated with en bloc excision and low-dose radiotherapy and indomethacine. The aim of this study was to explain the different diagnostic properties of myositis ossificans around the hip and non-classic causes of sciatica.

The role of MRI in image-guided needle biopsy of focal bone and soft tissue neoplasms

Magnetic resonance imaging (MRI) plays a critical role in the management pathway of both soft tissue and bone neoplasms, from diagnosis through to post-treatment follow-up. There are a wide range of surgical, oncological, and combined treatment regimes but these rely on accurate histopathological diagnosis. This article reviews the role of MRI in the planning of image-guided needle biopsy for suspected soft tissue and bone tumors.

A foreign body masquerading as a tumour

A 29-year-old man presented to his local orthopaedic service with a mass in the medial aspect of his left thigh, present for 1 year. It had not changed in size, although he complained of increasing tightness in the region. He denied any systemic symptoms or history of local trauma. Extensive imaging performed at his local hospital was thought suggestive of a musculoskeletal tumour. The patient was referred to our tertiary centre musculoskeletal tumour clinic. Review of external imaging and further investigations revealed a fluid-filled intramuscular mass containing an echogenic focus consistent with foreign body. Ultrasound-guided aspiration yielded fluid which grew Staphylococcus aureus. Only when presented with this information did the patient vaguely recall sitting on a wooden kebab stick 30 months previously. At surgery, a thick-walled abscess with a central foreign body was identified and drained. At follow-up 1 month later, he was well with no recurrent problems.

Skeletal muscle disease: patterns of MRI appearances

Although the presumptive diagnosis of skeletal muscle disease (myopathy) may be made on the basis of clinical-radiological correlation in many cases, muscle biopsy remains the cornerstone of diagnosis. Myopathy is suspected when patients complain that the involved muscle is painful and tender, when they experience difficulty performing tasks that require muscle strength or when they develop various systemic manifestations. Because the cause of musculoskeletal pain may be difficult to determine clinically in many cases, MRI is increasingly utilised to assess the anatomical location, extent and severity of several pathological conditions affecting muscle. Infectious, inflammatory, traumatic, neurological, neoplastic and iatrogenic conditions can cause abnormal signal intensity on MRI. Although diverse, some diseases have similar MRI appearances, whereas others present distinct patterns of signal intensity abnormality. In general, alterations in muscle signal intensity fall into one of three cardinal patterns: muscle oedema, fatty infiltration and mass lesion. Because some of the muscular disorders may require medical or surgical treatment, correct diagnosis is essential. In this regard, MRI features, when correlated with clinical and laboratory findings as well as findings from other methods such as electromyography, may facilitate correct diagnosis. This article will review and illustrate the spectrum of MRI appearances in several primary and systemic disorders affecting muscle, both common and uncommon. The aim of this article is to provide radiologists and clinicians with a collective, yet succinct and useful, guide to a wide array of myopathies.

Heterotopic ossification in the middle finger: a case report

A case of heterotopic ossification developed after traumatic laceration of the middle finger. It is extremely rare for heterotopic ossification to locate in the finger. The diagnosis was accomplished with plain radiographs as well as with MRI and confirmatory study with histopathological microscopic examination which demonstrated nubbin of bone surrounded by fibrovascular connective tissue, and the marrow was predominantly fatty with prominent ectatic vessels and patchy mild lymphocytic infiltrate and gross appearance of partly calcified bony tissue.

Serial MR imaging of intramuscular hematoma: experimental study in a rat model with the pathologic correlation

Objective

We wanted to demonstrate the temporal changes of the magnetic resonance imaging (MRI) findings in experimentally-induced intramuscular hematomas in rats and to correlate these data with the concurrent pathologic observations.

Materials and Methods

Intramuscular hematoma was induced in 30 rats. The MR images were obtained at 1, 4, 7 and 10 days and at 2, 3, 4, 6 and 8 weeks after muscle injury. The characteristic serial MRI findings were evaluated and the relative signal intensities were calculated. Pathologic specimens were obtained at each time point.

Results

On the T1-weighted imaging (T1WI), the intramuscular hematomas exhibited isointensity compared to that of muscle or the development of a high signal intensity (SI) rim on day one after injury. The high SI persisted until eight weeks after injury. On the T2-weighted imaging (T2WI), the hematomas showed high SI or centrally low SI on day one after injury, and mainly high SI after four days. A dark signal rim was apparent after seven days, which was indicative of hemosiderin on the pathology. The gradient echo (GRE) imaging yielded dark signal intensities at all stages.

Conclusion

Unlike brain hematomas, experimentally-induced intramuscular hematomas show increased SI on both the T1WI and T2WI from the acute stage onward, and this is pathologically correlated with a rich blood supply and rapid healing response to injury in the muscle. On the T2WI and GRE imaging, high SI with a peripheral dark signal rim is apparent from seven days to the chronic stage.

Magnetic resonance imaging in the visualization of benign tumors and tumor-like lesions of hand and wrist

The differential diagnosis of benign tumors and tumor-like lesions of the hand and wrist region is important with regard to choosing the therapy (medical versus surgical), or to decide to just follow-up the lesion. In most of the cases the proper analysis of MRI findings in correlation with the patient's history is sufficient to meet a specific diagnosis. However, diagnostic confusion is not uncommon as there are numerous lesions affecting the hand and wrist region. This pictorial essay offers a practical radiological approach to benign tumors and tumor-like lesions of the hand and wrist region based on most frequently observed MRI findings.

Histology and imaging of soft tissue sarcomas

Imaging and histology are two complementary morphological techniques which play a fundamental role in the diagnosis and management of soft tissue sarcomas. Imaging allows to identify some pseudosarcomatous benign lesions such as myositis ossificans, intramuscular hemangioma, angiomyolipoma, intramuscular lipoma, giant cell tumour of tendon sheath, desmoid tumour and elastofibroma. There is no formal criterion for diagnosing a sarcoma on magnetic resonance imaging (MRI) but malignancy is strongly suspected with the presence of necrosis and vascular, bone or joint invasion. Imaging may also suggest some histological types of sarcoma such as well-differentiated liposarcoma, dedifferentiated liposarcoma, synovial sarcoma or extraskeletal osteosarcoma. Imaging is also extremely helpful in determining the appropriate kind of sampling to carry out and in guiding the performance of a microbiopsy. The appearance observed on imaging should always be taken into consideration for the interpretation of the microbiopsy by the pathologist.

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.

Skeletal muscle metastases: primary tumours, prevalence, and radiological features

BACKGROUND

Although skeletal muscles comprise nearly 50% of the total human body mass and are well vascularised, metastases in the musculature are rare. The reported prevalence of skeletal muscle metastases from post-mortem studies of patients with cancer is inconstant and ranges from 0.03 to 17.5%.

MATERIALS AND METHODS

Of 5,170 patients with metastasised cancer examined and treated at our institution during the period from January 2000 to December 2007, 61 patients with muscle metastases (80 lesions) were identified on computed tomography (CT). Genital tumours (24.6%) were the most frequent malignancies metastasising into the skeletal musculature, followed by gastrointestinal tumours (21.3%), urological tumours (16.4%), and malignant melanoma (13.1%). Other primary malignancies were rarer, including bronchial carcinoma (8.2%), thyroid gland carcinoma (4.9%), and breast carcinoma (3.3%). In 8.2%, carcinoma of unknown primary was diagnosed.

RESULTS

Skeletal muscle metastases (SMM) were located in the iliopsoas muscle (27.5%), paravertebral muscles (25%), gluteal muscles (16.3%), lower extremity muscles (12.5%), abdominal wall muscles (10%), thoracic wall muscles (5%), and upper extremity muscles (3.8%). Most (76.3%) of the 80 SMM were diagnosed incidentally during routine staging CT examinations, while 23.7% were symptomatic.

CONCLUSION

Radiologically, SMM presented with five different types of lesions: focal intramuscular masses (type I, 52.5% of SMM), abscess-like intramuscular lesions (type II, 32.5%), diffuse metastatic muscle infiltration (type III, 8.8%), multifocal intramuscular calcification (type IV, 3.7%) and intramuscular bleeding (type V, 2.5%).

Ossifying lipoma of the thigh

Lipomas are common soft-tissue tumours that are usually found in the subcutaneous adipose tissue. Occasionally, they may contain mesenchymal elements other than adipose tissue, including osseous components. These ossifying lipomas are usually located near or within bone, and it is very rare for a lipoma with no connection to bone to contain mature osseous tissue. We describe a case of a symptomatic ossifying intramuscular lipoma of the thigh.