MRI characteristics of nodular fasciitis of the musculoskeletal system

Mid-thoracic Nodular Fasciitis: A Diagnostic Dilemma

Nodular fasciitis (NF) is a rare, benign, yet rapidly proliferative myofibroblastic soft tissue tumor that often mimics malignant lesions and presents significant diagnostic challenges. This case report describes a 16-year-old female whose mid-thoracic mass was initially mismanaged in an emergency setting as a sebaceous cyst. The misdiagnosis and subsequent inappropriate incision and drainage led to an iatrogenic flare-up, exacerbating the patient's condition and complicating her management course. The complexities encountered in this case underscore the critical need for stringent diagnostic protocols and multidisciplinary management to avoid iatrogenic complications and improve clinical outcomes in patients presenting with unusual soft tissue lesions. This report highlights the importance of adhering to established protocols for soft tissue lump evaluation and the potential pitfalls of misdiagnosis.

Ultrasound features and differential diagnosis for superficial nodular fasciitis

BACKGROUND

Nodular fasciitis (NF) has nonspecific clinical manifestations and is often misdiagnosed as sarcoma. The investigations of imaging methods for NF were limited.

OBJECTIVE

To analyze the ultrasound (US) features of NF, and to evaluate the diagnostic value of US for NF.

MATERIALS AND METHODS

A total of 61 NF patients were recruited retrospectively, and 551 lesions in the subcutaneous fat layer were included for comparison. We evaluated the ultrasound features of the patients and divided the NF cases into three types. Chi-square test or Fisher exact test were conducted to detect the potential difference in the distributions of three types in the two groups.

RESULTS

Among the 61 NF cases, 65.6% were in the upper extremities (n = 40). The proportion of type 1, 2, and 3 were 57.4%, 24.6%, and 18.0%, respectively. NF were significantly more likely locating in the upper extremities than the other soft tissue tumors (p < 0.001). Type 1 and type 2 of sonographic features were significantly more commonly observed in NF than other soft tissue tumors among the three types (p < 0.001).

CONCLUSION

The type 1 and type 2 of US features can help to distinguish NF from other lesions. US has great potential to improve the diagnostic accuracy and reduce the unnecessary surgery.

Development of clinical and magnetic resonance imaging-based radiomics nomograms for the differentiation of nodular fasciitis from soft tissue sarcoma

BACKGROUND

Accurate differentiation of nodular fasciitis (NF) from soft tissue sarcoma (STS) before surgery is essential for the subsequent diagnosis and treatment of patients.

PURPOSE

To develop and evaluate radiomics nomograms based on clinical factors and magnetic resonance imaging (MRI) for the preoperative differentiation of NF from STS.

MATERIAL AND METHODS

This retrospective study analyzed the MRI data of 27 patients with pathologically diagnosed NF and 58 patients with STS who were randomly divided into training (n = 62) and validation (n = 23) groups. Univariate and multivariate analyses were performed to identify the clinical factors and semantic features of MRI. Radiomics analysis was applied to fat-suppressed T1-weighted (T1W-FS) images, fat-suppressed T2-weighted (T2W-FS) images, and contrast-enhanced T1-weighted (CE-T1W) images. The radiomics nomograms incorporating the radiomics signatures, clinical factors, and semantic features of MRI were developed. ROC curves and AUCs were carried out to compare the performance of the clinical factors, radiomics signatures, and clinical radiomics nomograms.

RESULTS

Tumor location, size, heterogeneous signal intensity on T2W-FS imaging, heterogeneous signal intensity on CE-T1W imaging, margin definitions on CE-T1W imaging, and septa were independent predictors for differentiating NF from STS (P < 0.05). The performance of the radiomics signatures based on T2W-FS imaging (AUC = 0.961) and CE-T1W imaging (AUC = 0.938) was better than that based on T1W-FS imaging (AUC = 0.833). The radiomics nomograms had AUCs of 0.949, which demonstrated good clinical utility and calibration.

CONCLUSION

The non-invasive clinical radiomics nomograms exhibited good performance in the differentiation of NF from STS, and they have clinical application in the preoperative diagnosis of diseases.

Fibroblastic and Myofibroblastic Soft-Tissue Tumors: Imaging Spectrum and Radiologic-Pathologic Correlation

Fibroblastic and myofibroblastic tumors are a variable group of neoplasms ranging from benign to malignant. These lesions may affect patients of any age group but are more frequently encountered in the pediatric population. Patient clinical presentation depends on the location, growth pattern, adjacent soft-tissue involvement, and pathologic behavior of these neoplasms. In the 2020 update to the World Health Organization (WHO) classification system, these tumors are classified on the basis of their distinct biologic behavior, histomorphologic characteristics, and molecular profiles into four tumor categories: (a) benign (eg, fibrous hamartoma of infancy, nodular fasciitis, proliferative fasciitis, fibroma of the tendon sheath, calcifying aponeurotic fibroma); (b) intermediate, locally aggressive (eg, desmoid fibromatosis); (c) intermediate, rarely metastasizing (eg, dermatofibrosarcoma protuberans, myxoinflammatory fibroblastic sarcoma, low-grade myofibroblastic sarcoma, infantile fibrosarcoma); and (d) malignant (eg, sclerosing epithelioid fibrosarcomas; low-grade fibromyxoid sarcoma; myxofibrosarcoma; fibrosarcoma, not otherwise specified). Detection of various components of solid tumors at imaging can help in prediction of the presence of corresponding histopathologic variations, thus influencing diagnosis, prognosis, and treatment planning. For example, lesions with a greater myxoid matrix or necrotic components tend to show higher signal intensity on T2-weighted MR images, whereas lesions with hypercellularity and dense internal collagen content display low signal intensity. In addition, understanding the radiologic-pathologic correlation of soft-tissue tumors can help to increase the accuracy of percutaneous biopsy and allow unnecessary interventions to be avoided. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Fasciitis ossificans: imaging features, histology, and differential diagnosis

AIM

To describe the imaging features of fasciitis ossificans and its histopathological features.

MATERIALS AND METHODS

Using a word search of existing pathology reports at the Mayo Clinic, six cases of fasciitis ossificans were identified. The clinical history, histology, and available imaging of the affected area were reviewed.

RESULTS

Imaging consisted of radiographs, mammograms, ultrasound images, bone scintigraphs, computed tomography (CT), and magnetic resonance imaging (MRI) images. All cases demonstrated a soft-tissue mass. The characteristic MRI appearance was a T2 hyperintense enhancing mass with surrounding soft-tissue oedema. Peripheral calcifications were seen on radiographs, CT, and/or ultrasound. Histological sections showed distinct zonation, with nodular fasciitis-like zones of myofibroblastic proliferation, which merged with osteoblasts that rim the ill-defined trabeculae of woven bone and became continuous with the mature lamellar bone surrounded by a thin layer of compressed fibrous tissue.

CONCLUSION

Imaging features of fasciitis ossificans are that of an enhancing soft-tissue mass located within a fascial plane with prominent surrounding oedema and mature peripheral calcification. Imaging and histology are that of myositis ossificans but occurring within the fascia. It is important that radiologists are aware of the diagnosis of fasciitis ossificans and appreciate its similarity to myositis ossificans. This is particularly important in anatomical locations with fascias but no muscle. Given the radiographic and histological overlap between these entities, nomenclature that encompasses both could be considered in the future.

Nodular Fasciitis: False Positive on 18F-Piflufolastat and 11C-Choline PET/CT

ABSTRACT

PET/CT plays a crucial role in the management of prostate cancer with several emerging and established radiopharmaceuticals, including 18 F-piflufolastat and 11 C-choline. These radiotracers are thought to be relatively specific to prostate cancer; however, uptake has also been demonstrated in other benign and malignant lesions. Nodular fasciitis is a rapidly growing benign soft tissue neoplasm that is typically self-limiting. Although a few case reports describe 68 Ga-PSMA uptake in nodular fasciitis, uptake of 11 C-choline and other PSMA-targeted PET probes, including 18 F-piflufolastat, have not previously been reported. We present a novel case of nodular fasciitis demonstrating both 18 F-piflufolastat and 11 C-choline avidity.

Multimodality imaging features of USP6-associated neoplasms

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

A case report of an unusual temporomandibular joint mass: Nodular fasciitis

Nodular fasciitis (NF) is a benign myofibroblastic proliferation that grows very rapidly, mimicking a sarcoma on imaging. It is treated by local excision, and recurrence has been reported in only a few cases, even when excised incompletely. The most prevalent diagnoses of temporomandibular joint (TMJ) masses include synovial chondromatosis, pigmented villonodular synovitis, and sarcomas. Cases of NF in the TMJ are extremely rare, and only 3 cases have been reported to date. Due to its destructive features and rarity, NF has often been misdiagnosed as a more aggressive lesion, which could expose patients to unnecessary and invasive treatment approaches beyond repair. This report presents a case of NF in the TMJ, focusing on various imaging features, along with a literature review aiming to determine the hallmark features of NF in the TMJ and highlight the diagnostic challenges.

Arthroscopic treatment for intra-articular fibroma of the tendon sheath in a teenager

An adolescent female patient presented with atraumatic left knee pain and limited flexion. MRI demonstrated evidence of a soft tissue lesion abutting the posterior cruciate ligament. Differential diagnosis included pigmented villonodular synovitis (PVNS) and fibroma of the tendon sheath (FTS). Following arthroscopic biopsy, histopathological evaluation confirmed FTS. The tumour was then excised via an arthroscopic approach. This case report provides a unique example of FTS abutting the cruciate ligaments in an uncommonly young female patient. It highlights the importance of including benign processes, such as FTS, in the differential with more aggressive-type diagnoses like PVNS. Furthermore, this case exemplifies an appropriate surgical indication for FTS. Finally, it emphasises the importance of communication and collaboration among orthopaedic subspecialists in providing safe and effective arthroscopic treatment of this unique tumour presentation.

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.

Update on MR Imaging of Soft Tissue Tumors of Head and Neck

This article reviews soft tissue tumors of the head and neck following the 2020 revision of WHO Classification of Soft Tissue and Bone Tumours. Common soft tissue tumors in the head and neck and tumors are discussed, along with newly added entities to the classification system. Salient clinical and imaging features that may allow for improved diagnostic accuracy or to narrow the imaging differential diagnosis are covered. Advanced imaging techniques are discussed, with a focus on diffusion-weighted and dynamic contrast imaging and their potential to help characterize soft tissue tumors and aid in distinguishing malignant from benign tumors.

Two case reports of intra-articular nodular fasciitis of the knee confirmed by MYH9-USP6 gene fusion expression

AIM

To describe two cases of intra-articular nodular fasciitis (NF) which developed within the knee joint and were associated with the expression of the MYH9-USP6 gene fusion.

PATIENTS AND METHODS

Two women, 30 and 56 years of age, with no history of joint disease or knee joint trauma, are presented in our cases. We report these cases describing the clinical presentation, assessment, histopathological examination, gene expression, and clinical management.

RESULTS

Both patients presented with knee pain and limitation in the range of flexion. We diagnosed our two cases as intraarticular nodular fasciitis based on histological findings and by the detection of the MYH9-USP6 gene fusion. The transcript of MYH9-USP6 gene fusion was identified by RT-PCR and direct sequencing in both cases.

CONCLUSION

We report the first cases of intra-articular NF involving the knee joint, with identification of a MYH9-USP6 gene fusion by RT-PCR. NF should be considered in the differential diagnosis of intra-articular lesions.

Ultra-high-frequency ultrasound of superficial and musculoskeletal structures in the pediatric population

Because of its relatively low cost, lack of ionizing radiation and great versatility, US is considered the imaging modality of choice to evaluate a large variety of pediatric conditions. Imaging of superficial structures and small anatomical parts can be at times limited with standard US. Recent advances in technology yielded ultra-high-frequency US systems that are capable of scanning with frequencies as high as 70 MHz and resolutions of 30 μm. This technology, approved by the United States Food and Drug Administration, has not been widely used in the clinical setting. It has the potential to become a powerful diagnostic tool in clinical practice, especially in the evaluation of infants, given their inherent body habitus. Our main objective is to discuss the use of ultra-high-frequency US at a tertiary care center. This pictorial essay presents a gamut of pediatric pathologies pertaining to imaging of the soft tissues and the superficial and musculoskeletal structures. Our aim in this pictorial essay is to highlight and illustrate the role of ultra-high-frequency US in improving the depiction of common and less common pathologies. We think it also helps to gain a new understanding of the normal anatomy in the pediatric population and to display specific features not shown by standard US and, in certain cases, ones that lead to a change in diagnosis.

Tumors and pseudotumors of the soft tissues: Imaging semiology and strategy

The aims of this educational review are to learn the semiological basis of soft-tissue lesions and, with the help of diagnostic algorithms, to apply the current recommendations for the management of soft-tissue tumors. Pseudotumors must first be identified and excluded. Among primary tumors, the search for macroscopic fat content on MRI is decisive; since it restricts the diagnostic range to adipocytic tumors. Key imaging features of non-adipocytic tumors are highlighted. When a deep soft-tissue mass is found, therapeutic abstention or simple monitoring is only appropriate when there is diagnostic certainty: This is only the case for typical pseudotumors, typical benign tumors, and fat tumors without atypical criteria. In all other cases, histological evidence is required. If there is any suspicion of soft-tissue sarcoma or any undetermined lesion, the patient should be referred to a sarcoma referral center before biopsy.

The accuracy of a novel sonographic scanning and reporting protocol to survey for soft tissue sarcoma local recurrence

OBJECTIVE

This study aims to determine the accuracy of a novel ultrasonography (US) scanning and reporting protocol to detect recurrences. The secondary aim is to compare US and MRI accuracy and agreement.

MATERIALS AND METHODS

In this IRB-approved prospective study, consecutive patients presenting for MRI surveillance after resection were enrolled and underwent same-day US. Blinded to clinical information and the MRI, the US scanner characterized lesions using a proposed novel lexicon. Outcome was defined either by histology or a subsequent MRI scan confirming the presence or absence of recurrence. Fisher's exact test and Kappa test were performed to assess of the significance and agreement between US, MRI, and outcome.

RESULTS

A total of 68 US scans were performed on 55 patients. The overall accuracy to diagnose recurrence was the same for US and MRI (92.6%) while US was less sensitive (75.0% vs. 91.7%) but more specific (97.6% vs. 92.9%) than MRI. The two lesions missed by US but not MRI were an entirely intraosseous metastasis and a subcentimeter skin nodule. There was strong agreement between US and MRI with outcome (k = 0.787 and 0.801, respectively).

CONCLUSIONS

These pilot data suggest the accuracy of this novel US local recurrence surveillance method is comparable to MRI. A multi-institutional prospective trial would increase power and determine reproducibility.

MR imaging features and a redefinition of the classification system for nodular fasciitis

To analyze magnetic resonance imaging features of nodular fasciitis and redefine the system for classifying this class of lesions.Twenty-seven patients with nodular fasciitis and 71 patients with other soft tissue lesions who underwent surgery or biopsy were retrospectively analysed. Demographic information, medical history, and magnetic resonance imaging features were collected. Classification of nodular fasciitis was performed based on a redefined system. Comparison between 2 groups was performed with Chi-square or Fisher exact test.For nodular fasciitis, the longest average lesion diameter was 1.87 cm (range, 0.52-5.46 cm), and 40.7% of lesions were located in the upper extremities, while 29.6% were located in the head and neck. Compared with skeletal muscle, most lesions exhibited isointensity on T1-weighted imaging and hyperintensity on T2-weighted imaging, and 45.5% of the lesions exhibited rim enhancement, 40.9% showed obvious homogenous enhancement, while 13.6% showed no enhancement or slight enhancement. The subcutaneous type accounted for 25.9% of cases, the fascial type 25.9%, the intramuscular type 29.6%, and the unclassified type 18.5%. The "fascia tail sign" was more frequently observed in nodular fasciitis than in other soft tissue lesions (P < .001). Nodular fasciitis was slightly more likely to present with the "inverted target sign" and "solar halo sign" than other soft tissue lesions (P > .05). The "cloud sign" only appeared in nodular fasciitis (P < .05).The "fascia tail sign" and "cloud sign" could help differentiate nodular fasciitis from other soft tissue lesions. A new classification may improve understanding about nodular fasciitis.

Benign infiltrative myofibroblastic neoplasms of childhood with USP6 gene rearrangement

AIMS

Several morphologically overlapping (myo)fibroblastic neoplasms harbour USP6 fusions, including aneurysmal bone cysts, nodular fasciitis, myositis ossificans, cranial fasciitis, fibro-osseous pseudotumour of the digits, and cellular fibroma of the tendon sheath. USP6-induced neoplasms are almost universally benign and cured by local excision. We aim to highlight the diagnostic value of USP6 fusion detection in a series of aggressive-appearing paediatric myofibroblastic tumours.

METHODS AND RESULTS

Three deep-seated, radiographically aggressive, and rapidly growing childhood myofibroblastic neoplasms were morphologically and molecularly characterised by USP6 break-apart fluorescence in-situ hybridisation (FISH), transcriptome sequencing, and targeted capture analysis. Each tumour occurred in the lower-extremity deep soft tissue of a child presenting with pain, limping, or a mass. In all three patients, imaging studies showed a solid mass that infiltrated into surrounding skeletal muscle or involved/eroded underlying bone. The biopsied tumours consisted of variably cellular myofibroblastic proliferations with variable mitotic activity that lacked overt malignant cytological features. FISH showed that all tumours had USP6 rearrangements. On the basis of these results, all three patients were treated with conservative excision with positive margins. The excised tumours had foci resembling nodular fasciitis, fibromatosis, and pseudosarcomatous proliferation. Next-generation sequencing revealed COL1A1-USP6 fusions in two tumours and a COL3A1-USP6 fusion in the third tumour. One tumour had a subclonal somatic APC in-frame deletion. No recurrence was observed during follow-up (8-40 months).

CONCLUSION

We present a series of benign, but aggressive-appearing, USP6-rearranged myofibroblastic tumours. These deep-seated tumours had concerning clinical and radiographic presentations and did not fit into one distinct histological category. These cases highlight the diagnostic value of USP6 fusion detection to identify benign nondescript tumours of this group, especially those with aggressive features, to avoid overtreatment.

Simultaneous bifocal and asymptomatic intramuscular nodular fasciitis of the thigh: A case report

Nodular fasciitis (NF) is a rapid-growth benign that is misdiagnosed as sarcoma and leads to overtreatment. The spontaneous regression of NF is a possible phenomenon. "Wait and see" ideal is one of the treatment strategies of NF.

Intraarticular Nodular Fasciitis of the Knee With MHY9-USP6 Fusion: A Case Report

Background. Nodular fasciitis (NF) is a self-limiting, benign mesenchymal neoplasm of fibroblastic/myofibroblastic origin. Due to the fast growth, cellularity, and frequently observed high mitotic count, it is commonly misdiagnosed as a sarcoma, often resulting in overtreatment. Intraarticular examples of NF are extremely rare. Radiologically, NF can mimic fibroma of the tendon sheath, tenosynovial giant cell tumor, and synovial chondromatosis. Histology can vary from hypercellular, mitotically active lesions to fibrotic, less cellular ones, and can, therefore, mimic other benign and low-grade malignant neoplasms. Recently, the MYH9-USP6 fusion has been found in up to 92% of NF. Case Presentation. In this article, we report a case of a 38-year-old patient with an intraarticular lesion, radiologically suspicious of tenosynovial giant cell tumor. Histology demonstrated a spindle cell lesion composed of fibroblasts/myofibroblasts embedded in a highly collagenous/hyalinized stroma, partly arranged in short fascicles. Extravasated erythrocytes and rare mitotic figures were present. Immunohistochemically, tumor cells expressed smooth muscle actin and were negative for desmin, β-catenin, CD34, and SOX10. These findings rendered the diagnosis of NF. Molecular analysis using next-generation sequencing (Archer FusionPlex Sarcoma Panel) revealed gene rearrangement involving USP6 and MYH9 supporting the diagnosis of NF in the knee joint. Conclusions. Radiological and histological features of NF can overlap with other benign and low-grade malignant lesion. Identification of the USP6 gene rearrangements or finding of the MYH9-USP6 fusion, especially in core needle biopsies and in the lesions occurring at unusual sites, can result in adequate therapeutic approach avoiding overtreatment.

A case of nodular fasciitis that was difficult to distinguish from sarcoma

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Nodular fasciitis is difficult to distinguish from sarcoma.

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Clinical and pathological findings may not correspond, as in our case.

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If sarcoma cannot be excluded, treatment should consider the risk of malignancy.

Introduction

Nodular fasciitis is a reactive proliferative lesion. It is often difficult to distinguish from sarcoma, such as malignant peripheral nerve sheath tumor (MPNST). Therefore, both pathological findings and clinical features must be considered.

Presentation of case

A 75-year-old man presented with a 1 × 1 cm mass on his left forearm that had enlarged rapidly without specific symptoms. Magnetic resonance imaging revealed a mass adjacent to brachioradialis. The lesion showed iso-intensity to muscle on T1-weighted images and hyperintensity on T2-weighted images. We made a clinical diagnosis of nodular fasciitis. Under observation, the mass gradually decreased in size and disappeared after two months. Four years later, another lesion appeared at the same site. We performed total excisional biopsy and histopathological examination indicated low grade MPNST or recurrent nodular fasciitis. Since malignancy could not be excluded, wide resection was performed. At 4 years postoperatively, there has been no recurrence.

Discussion

In this patient, nodular fasciitis of the right forearm was diagnosed clinically and showed spontaneous regression. However, recurrence was noted after four years. While the clinical features suggested recurrent nodular fasciitis, pathological findings indicated the possibility of low grade MPNST.

Conclusion

When it is difficult to determine whether a lesion such as nodular fasciitis is benign or malignant, the patient should be managed by considering the possibility of malignancy.

Case of mesenchymal tumor with the PPP6R3-USP6 fusion, possible nodular fasciitis with malignant transformation

Nodular fasciitis (NF) is a self-limiting benign disease that is characterized by rapid proliferation of fibroblastic and myofibroblastic cells. The characteristic gene fusion containing the USP6 gene is a genetic hallmark of NF and MYH9-USP6 is the most frequent fusion, suggesting that NF is not a reactive condition but a neoplastic disease. Malignant transformation of NF has been reported rarely as a single case associated with the PPP6R3-USP6 fusion. Here we report a case of soft part tumor of which the histological feature was a typical NF but showed aggressive and non-regressing growth with local invasion. Targeted RNA sequencing and fluorescence in situ hybridization analysis identified PPP6R3-USP6 with gene amplification. These findings indicate that the present case is the second case of malignant NF, and we suggest potential malignant transformation in certain NF cases.

Fibroma of the patellar tendon sheath-a rare case in a young boy

Fibroma of the tendon sheath is a rare benign fibrocollagenous soft tissue tumor, arising predominantly from the synovium of tendon sheath. Fibromas occur most commonly in relation to the tendons of the fingers, hand, and the wrist. Fibromas related to large joints are rather rare and though amongst the large joints, the knee is a common site. Fibromas of the patellar tendon sheath, specifically, are very rare. To the best of our knowledge, only three cases of fibromas arising from the patellar tendon sheath have been reported in the relevant English medical literature. Herein we describe the fourth biopsy-proven case of fibroma of patellar tendon sheath in a 6-year-old boy.

Ossifying fasciitis at an extraordinary site - a case report and analysis of diagnostic pitfalls

Ossifying fasciitis is a very rare disease of reactive character; however, it can mimic malignant lesions, especially osteosarcoma. We report a case of a 30-year-old woman, who experienced a rapidly growing painful lesion of the left knee joint, preceded by a trauma. The tumor was resected, and the histopathological image suggested a malignant lesion with features of an osteosarcoma. A detailed correlation with a clinicopathological and radiological analysis led to the final diagnosis of ossifying fasciitis at an extraordinary site of patellar retinaculum. Our case shows that the close similarity between ossifying fasciitis and osteosarcoma may be challenging.

Imaging findings of radiologically misdiagnosed nodular fasciitis

BACKGROUND

Nodular fasciitis rarely occurs in young adults and children; it usually resembles other tumors, even malignancy.

PURPOSE

To review the imaging findings of six cases of nodular fasciitis misdiagnosed radiologically.

MATERIAL AND METHODS

The clinical and radiologic features of six cases of histologically proven but radiologically misdiagnosed nodular fasciitis were reviewed retrospectively. Two cases underwent both plain and enhanced computed tomography (CT) scans and the other four had both regular and enhanced magnetic resonance (MR) scans.

RESULTS

All six patients were young (five children and one young adult). A rapid growing mass, pain or painless, was the most frequent presentation. Most masses were oval, well-defined, and homogeneous, with an average diameter of 2.2 cm. Five were found in superficial fascia with a broad base. Two cyst-like masses showed hypodensity relative to muscle on plain CT and without enhancement. Compared to muscle, these masses showed isointensity (n = 3) or slight hyperintensity (n = 1) on T1-weighted imaging, hyperintensity on T2-weighted imaging (n = 4), with homogeneous notable enhancement (n = 3) or mild enhancement (n = 1). Five (83.3%) were found with a "fascial tail" sign characterized as thickening of adjacent fascial layer with notable enhancement. One mass showed an "inverted target" sign.

CONCLUSION

Nodular fasciitis in young adults and children is usually superficial, rapid growing, well-defined, and homogeneous, frequently with a "fascial tail" sign. Radiologically, it can resemble a benign cyst and might be easily misdiagnosed. Therefore, nodular fasciitis should be remembered in the differential diagnosis for superficial soft tissue tumor found in young adult and children.

Nodular fasciitis mimicking a soft tissue sarcoma - A case report

INTRODUCTION

Nodular Fasciitis, also known as infiltrative or pseudosarcomatous fasciitis, is a benign soft tissue tumour of fibroblastic/myofibroblastic differentiation, that was first described in 1955 by Konwaler et al. PRESENTATION OF CASE: This is a case report of a 27-year old male with complaints of a swelling in the right axilla for 2 and ½ years measuring 12 cm × 10 cm. Chest X-Ray was normal. Magnetic Resonance Imaging of the right arm and chest showed an irregular mass in the axilla in the muscular-subcutaneous plane measuring 10.8 cm × 8.8 cm × 12 cm, with no neural involvement. Magnetic Resonance Angiogram showed feeders from the branches of the Right Subclavian and Right Axillary Artery and venous drainage into the Right Subclavian Vein. USG guided biopsy was done which showed benign spindle cell neoplasm. Patient underwent wide local excision under general anesthesia. The specimen was sent for histopathological examination which showed histological and immunohistochemical features in favour of Nodular Fasciitis.

DISCUSSION

Most nodular fasciitis lesions are solitary and occur in adults 20-40 years of age. Nodular fasciitis affects both men and women with equal frequency. Differential diagnosis of nodular fasciitis includes, fibrosarcoma, fibroma, fibrous histiocytoma, and desmoids and histopathology and immunohistochemistry play a key role in identifying the condition.

CONCLUSION

Owing to the size, location and findings of the Magnetic Resonance Angiogram we initially suspected a Soft Tissue Sarcoma, but to our surprise, on further investigation the mass was revealed to be Nodular Fasciitis.

USP6 activation in nodular fasciitis by promoter-swapping gene fusions

Nodular fasciitis is a self-limited myofibroblastic lesion that can be misdiagnosed as a sarcoma as a result of its rapid growth, cellularity, and sometimes prominent mitotic activity. A recurrent translocation t(17;22) has been identified in nodular fasciitis, fusing the coding region of USP6 to the promoter region of MYH9, and resulting in increased USP6 expression. A subset of cases show USP6 rearrangement without the typical fusion variants by RT-PCR, or any MYH9 rearrangement by FISH. We sought to further characterize such tumors using molecular diagnostic assays. A novel RT-PCR assay was designed to detect the two known MYH9-USP6 fusion types in formalin-fixed paraffin-embedded and frozen tissue, and a break-apart FISH assay was designed to detect USP6 rearrangement. Twenty-six cases of nodular fasciitis diagnosed between 2002 and 2013 were retrieved from the pathology files of our institutions and were confirmed to be positive by FISH and/or RT-PCR. Seven samples showed USP6 rearrangement by FISH but were negative for MYH9-USP6 fusion by RT-PCR; these cases were subjected to a next-generation sequencing assay utilizing anchored multiplex PCR technology. This assay targets a single partner gene associated with fusions in bone and soft tissue tumors for agnostic detection of gene fusion partners. Novel fusion partners were identified in all seven cases and confirmed by RT-PCR. Structurally, all fusions consisted of the juxtaposition of the entire coding region of USP6 with the promoter of the partner gene, driving increased USP6 expression. This study confirms the neoplastic nature of nodular fasciitis, defines additional pathogenic fusion partners, and adds to the growing body of literature on USP6-associated neoplasia. Given the diagnostic challenges of these tumors, molecular assays can be useful ancillary tools; however, the prevalence of promoter swapping must be recognized when interpreting results.

Sonographic appearance of proliferative fasciitis---A case report

Proliferative fasciitis is a benign entity involving the subcutaneous tissues and fascias, characterized by the proliferation of fibroblast-like spindle cells and ganglion-like cells. However, proliferative fasciitis may be easily confused with sarcoma clinically and pathologically, because it appears as a rapidly growing painful mass and has histologic features such as high cellularity, bizarre morphologic patterns, mitotic figures, and diffuse infiltrative proliferation. Imaging findings of proliferative fasciitis have been very rarely reported. We report the sonographic findings in a case of proliferative fasciitis in a 43-year-old woman with histopathological correlation. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:445-449, 2017.

Fibroma of tendon sheath around large joints: clinical characteristics and literature review

Background

Fibroma of tendon sheath (FTS) is a benign tumor arising from the synovium of the tendon sheath that occurs mostly around small joints such as the fingers, hands, and wrist. However, FTS rarely arises around a large joint (knee, shoulder, elbow, and ankle) with intra-articular or extra-articular involvement. The clinical characteristics of FTS arising around a large joint are unclear. An additional 3 cases of FTS arising around a large joint are presented. Furthermore, the published cases and the present cases are reviewed with respect to their clinical characteristics and imaging and histopathology findings.

Methods

The 43 reported cases including the present 3 patients were summarized, and the patients’ profiles, symptoms, sites and locations in the joint involved by FTS, magnetic resonance imaging (MRI) findings, surgical procedures, clinical courses, and cytogenetic analyses were reviewed.

Results

The average age of 26 cases was 40.9 years (range 13–69 years), and about 60% of the patients were male. About 10% of the patients had a past history of trauma to the knee joint. Of the present 3 cases, one case was extra-articular around the elbow joint, one case was extra-articular around the knee joint, and one case was intra-articular involving the knee joint. The common symptoms were pain (62.5%), swelling or palpable mass (54.2%), and limited range of motion of the involved joint (50%). The most commonly involved joint was the knee, with 32 cases (74.4%), followed by the elbow in 5 cases (11.6%), ankle in 4 (9.3%), and shoulder in 2 (4.7%). The tumor typically exhibited iso to low signal intensity on T1-weighted MRI. T2-weighted images showed various patterns, but mostly low signal intensity relative to muscle. The surgical margin was marginal resection in all cases. There were no recurrences after surgery. On chromosomal analysis, only the present Case 3 showed an abnormality.

Conclusions

A total of 43 FTS cases that occurred around large joints were summarized. The most common site was around the knee joint. In FTS cases around large joints, it is necessary to distinguish between various fibroblastic and/or fibrohistiocytic tumors.

Nodular Fasciitis of the Posterior Chest Wall With Bone Invasion Mimicking a Malignant Neoplasm

Nodular fasciitis is a self-limiting benign fibroblastic/myofibroblastic proliferation, which typically presents as a rapidly growing mass resembling an aggressive lesion clinically. It can also mimic a sarcoma histologically, hence the frequent characterization as "pseudosarcoma." We describe a case of a 53-year-old man who presented with a posterior chest wall mass that on imaging showed erosion into the adjacent ribs. After resection, the diagnosis of nodular fasciitis was rendered. Bone erosion by nodular fasciitis is extremely rare and can resemble a malignant neoplasm radiologically.

Nodular Fasciitis: Sonographic-Pathologic Correlation

We evaluated nodular fasciitis (NF) in 19 patients, focusing on the correlation between its sonographic and histopathologic features. Sonograms were retrospectively reviewed, and the location, shape, margin, echogenicity, echogenic rim, peripheral hyper-echoic nodules, posterior enhancement and vascularity of the lesions were recorded. In the histopathologic analysis, three patterns-infiltrating, pushing border and well circumscribed-were identified, and culture-like tissue centers were classified according to the distribution of focal keloid-like collagen bundles: uneven or even. For the sonographic-pathologic correlation, most NF cases were inhomogeneously hypo-echoic and had an echogenic rim, with an infiltrating or pushing border pattern. In addition, all NF cases with the infiltrating pattern were observed to have peripheral hyper-echoic nodules in sonograms. Thus, echogenic rims may be associated with the peripheral adipose tissues in infiltrating pattern, and the degree of infiltration may be associated with specific sonographic features of NF.

MR Imaging of Soft-Tissue Tumors of the Upper Extremity

Certain soft-tissue tumors seem to be specific to the upper extremity; most are benign. Knowledge of key magnetic resonance features, with clinical history and epidemiologic knowledge, can assist the radiologist in establishing optimal diagnosis. Indeterminate lesions require biopsy to exclude malignancy.

Multifocal nodular fasciitis of the hand and shoulder: case report

We report a case of nodular fasciitis occurring on the dorsum of the right middle finger, the dorsum of the right hand, and the right upper back associated with cortical erosions of the scapula. Ray amputation of the middle finger and marginal excision of the hand and periscapular masses were performed. There was no recurrence of the tumor at either site a year later.

Focal hand lesions: review and radiological approach

Focal hand lesions are commonly encountered in clinical practice and are often benign. Magnetic resonance (MR) imaging is the imaging modality of choice in evaluating these lesions as it can accurately determine the nature of the lesion, enhancement pattern and exact location in relation to surrounding tissues. However, while MR features of various soft tissue lesions in the hand have been well described, it is often still difficult to differentiate between benign and malignant lesions. We review the MR imaging features of a variety of focal hand lesions presenting at our institution and propose a classification into "benign", "intermediate grade" (histologically benign but locally aggressive with potential for recurrence) and frankly "malignant" lesions based on MR findings. This aims to narrow down differential diagnoses and helps in further management of the lesion, preoperative planning and, in cases of primary malignancy, local staging. Teaching Points • Hand lesions are often benign and MR is essential as part of the workup. • MR features of various hand lesions are well described but are often non-specific. • Certain MR features may help for the diagnosis but histological examination is usually required. • We aim to classify hand lesions based on MR features such as margin, enhancement and bony involvement. • Classifying these lesions can help narrow down differential diagnoses and aid management.

Intra-articular fibroma of tendon sheath arising in the acromioclavicular joint

Fibroma of the tendon sheath, a rare benign soft tissue tumor that most often occurs in the distal upper extremities (hands and wrist), is exceedingly rare to present as an intraarticular mass. Presented here is the first case in the English literature, to our knowledge, of a fibroma of the tendon sheath arising in the acromioclavicular joint. The patient presented with recurrent shoulder pain with activity without antecedent trauma. Radiographs were essentially normal. MR images demonstrated a lobulated, heterogeneous mass with contrast enhancement arising from the acromioclavicular joint. Following surgical resection, histopathology revealed hypocellular collagen matrix with spindle-shaped fibroblasts, confirming the diagnosis of fibroma of tendon sheath. The imaging features of the fibroma of the tendon sheath and a brief review of the literature are presented.

Nodular fasciitis: characteristic imaging features on sonography and magnetic resonance imaging

OBJECTIVES

The purpose of this study was to evaluate the imaging features of nodular fasciitis on sonography and magnetic resonance imaging (MRI).

METHODS

A retrospective search of the radiologic and pathologic databases over the past 10 years for the diagnosis of nodular fasciitis was performed. Sonographic and MRI features were described. Pathologic specimens were reviewed.

RESULTS

Six pathologically confirmed cases of nodular fasciitis were found. The mean patient age was 19.5 years (range, 8-33 years); 3 patients were male and 3 were female. Four patients had sonography only; 1 patient had both sonography and MRI; and 1 patient had MRI only. Three masses were located in the subcutaneous tissue adjacent to fascia; 2 were at the subcutaneous/muscular border; and 1 was intramuscular; however, all were in contact with fascia and showed a fascial tail on sonography and MRI. On sonography and MRI, masses were oval with poorly defined lobulated borders, averaging 2.6 cm (range, 1.8-3.5 cm). On sonography, all masses were hypoechoic. On MRI, the masses were isointense to muscle on T1-weighted sequences, hyperintense to muscle on fluid-sensitive sequences, and enhanced avidly but heterogeneously. The masses were surrounded by fat.

CONCLUSIONS

When a rapidly growing oval mass in contiguity with a fascial plane is recognized, the diagnosis of nodular fasciitis should be entertained. More importantly, the possibility of an inaccurate diagnosis by core biopsy exists, which may warrant gross resection.

[Nodular fasciitis: case report and review of the literature]

Among soft tissue tumors, nodular fasciitis is a relatively common tumor process, which occurs in the 30 first years of life. Nodular fasciitis is a benign tumor with a rapid proliferation of myofibroblastic cells, which develops at the expense of a muscular fascia in the subcutaneous tissue. Usual localizations are the trunk and upper limbs. Difficulty of diagnosis consists in the need to eliminate many differential diagnoses especially malignant tumor processes. From a clinical point of view, the rapid development of nodular fasciitis (from some days to some weeks) must fear a malignant process. This benign lesion, which does not recur (even if incomplete resection), may regress spontaneously. We report such a tumor located at the cubital fossa confirmed by a pathological examination.