The Clinical, Radiological, and Histopathological Characteristics of Intramuscular Myxoma: A Case Report.

In this study, we discuss the clinical, radiological, and histopathological characteristics of intramuscular myxomas (IMM), a rare form of benign soft tissue tumors. We report the case of a 47-year-old female patient presenting with a painless, non-inflammatory mass in the right thigh, which was mobile relative to both superficial and deep planes. Imaging, biopsy, and subsequent histopathological study established the diagnosis of intramuscular myxoma. The patient underwent surgical excision of the mass, with a straightforward postoperative course. It is important to distinguish IMM from malignant tumors, such as soft tissue sarcomas, through comprehensive examinations including imaging and biopsy. The recommended treatment is surgery for complete excision of the mass, with an exceptionally low recurrence rate.

Intramuscular Myxoma of the Flexor Carpi Ulnaris Causing Cubital Tunnel Syndrome: A Case Report.

Introduction: Intramuscular myxomas are rare, benign mesenchymal tumors which commonly arise in muscle of the upper limb, pelvis, abdominal tissue, spine, or facial muscle. There are few case reports of intramuscular myxomas, and none of these describe intramuscular myxoma as a cause of compressive neuropathy. Case Report: We describe the case of a 67-year-old woman who presented to us with a 1-year history of progressive enlargement of a painless right elbow mass. She gradually developed increasing numbness and tingling in her right small finger, which was worse at night. She underwent cubital tunnel release with concurrent right elbow mass excision of the flexor carpi ulnaris muscle. Histology showed intramuscular myxoma. Postoperatively, she had a complete resolution of her symptoms with a good functional outcome. Conclusion: This is the first known case of intramuscular myxoma within the flexor carpi ulnaris causing compressive neuropathy of the ulnar nerve at the elbow.

Mazabraud's syndrome in female patients: Two case reports.

BACKGROUND: Mazabraud's syndrome (MS) is a rare and slowly progressive benign disease characterized by the concurrent presence of fibrous dysplasia of bone and intramuscular myxoma, and is thought to be associated with mutations of the GNAS gene. To date, only about 100 cases of MS have been reported in the literature, but its standard treatment strategy remains unclear. CASE SUMMARY: We report two cases of MS in young women who underwent different treatments based on their symptoms and disease manifestations. The first patient, aged 37, received internal fixation and intravenous bisphosphonate for a pathological fracture of the right femoral neck, excision of a right vastus medialis myxoma was subsequently performed for pain control, and asymptomatic psoas myxomas were monitored without surgery. Genetic testing confirmed a GNAS gene mutation in this patient. The second patient, aged 24, underwent right vastus intermedius muscle myxoma resection, and conservative treatment for fibrous dysplasia of the ilium. These patients were followed-up for 17 months and 3 years, respectively, and are now in a stable condition. CONCLUSION: Various treatments have been selected for MS patients who suffer different symptoms. The main treatment for myxomas is surgical resection, while fibrous dysplasia is selectively treated if the patient experiences pathological fracture or severe pain. However, given the documented instances of malignant transformation of fibrous dysplasia in individuals with MS, close follow-up is necessary.

The Role of Methylation Analysis in Distinguishing Cellular Myxoma from Low-Grade Myxofibrosarcoma.

Cellular myxoma is a benign soft tissue tumor frequently associated with GNAS mutation that may morphologically resemble low-grade myxofibrosarcoma. This study aimed to identify the undescribed methylation profile of cellular myxoma and compare it to myxofibrosarcoma. We performed molecular analysis on twenty cellular myxomas and nine myxofibrosarcomas and analyzed the results using the methylation-based DKFZ sarcoma classifier. A total of 90% of the cellular myxomas had GNAS mutations (four loci had not been previously described). Copy number variations were found in all myxofibrosarcomas but in none of the cellular myxomas. In the classifier, none of the cellular myxomas reached the 0.9 threshold. Unsupervised t-SNE analysis demonstrated that cellular myxomas form their own clusters, distinct from myxofibrosarcomas. Our study shows the diagnostic potential and the limitations of molecular analysis in cases where morphology and immunohistochemistry are not sufficient to distinguish cellular myxoma from myxofibrosarcoma, particularly regarding GNAS wild-type tumors. The DKFZ sarcoma classifier only provided a valid prediction for one myxofibrosarcoma case; this limitation could be improved by training the tool with a more considerable number of cases. Additionally, the classifier should be introduced to a broader spectrum of mesenchymal neoplasms, including benign tumors like cellular myxoma, whose distinct methylation pattern we demonstrated.

Genetic characterization of intramuscular myxomas.

Introduction: Intramuscular myxomas are benign tumors that are challenging to diagnose, especially on core needle biopsies. Acquired chromosomal aberrations and pathogenic variants in codon 201 or codon 227 in GNAS complex locus gene (GNAS) have been reported in these tumors. Here we present our genetic findings in a series of 22 intramuscular myxomas. Materials and methods: The tumors were investigated for the presence of acquired chromosomal aberrations using G-banding and karyotyping. Pathogenic variants in codon 201 or codon 227 of GNAS were assessed using direct cycle Sanger sequencing and Ion AmpliSeq Cancer Hotspot Panel v2 methodologies. Results: Eleven tumors carried chromosomal abnormalities. Six tumors had numerical, four had structural, and one had both numerical and structural chromosomal aberrations. Gains of chromosomes 7 and 8 were the most common abnormalities being found in five and four tumors respectively. Pathogenic variants in GNAS were detected in 19 myxomas (86%) with both methodologies. The detected pathogenic variants were p.R201H in nine cases (seven with abnormal and two with normal karyotypes), p.R201C in five cases, all with normal karyotypes, p.R201S in three cases (two with abnormal and one with normal karyotype), p.R201G in one case with a normal karyotype, and p.Q227E in one case with a normal karyotype. Conclusion: Firstly, our data indicate a possible association between chromosomal abnormalities and GNAS pathogenic variants in intramuscular myxomas. Secondly, the presence of the rare pathogenic variants R201S, p.R201G and p.Q227E in 26% (5 out of 19) of myxomas with GNAS pathogenic variants shows that methodologies designed to detect only the common "hotspot" of p.R201C and p.R201H will give false negative results. Finally, a comparison between Ion AmpliSeq Cancer Hotspot Panel v2 and direct cycle Sanger sequencing showed that direct cycle Sanger sequencing provides a quick, reliable, and relatively cheap method to detect GNAS pathogenic variants, matching even the most cutting-edge sequencing methods.

Intramuscular myxoma of the thigh: A case report.

Intramuscular Myxomas are rare benign soft tissue tumors which usually occur between the ages 40 and 70 years and are more common among females. A thorough history and examination can help with diagnosis and it can be confirmed via histological examination. A 40-year-old female presented with a swelling in the medial aspect of right thigh which measured about 5 × 5 cm. Ultrasound, magnetic resonance imaging, and histopathology examination confirmed the diagnosis and a complete surgical resection was performed to remove the mass. Intramuscular myxoma should be included in differential diagnosis of sarcomas, hemangioma, desmoid tumor, clear cell sarcoma, and lipomas. Magnetic resonance imaging should be the investigation of choice, and histopathology remains the gold standard of investigation. Complete surgical excision with negative margins is the treatment of choice.

Nerve sheath myxoma masqueraded as intramuscular myxoma: an extremely rare tumor with unusual location - a case report and literature review.

Nerve sheath myxoma (NSM) is a very rare benign nerve sheath tumor that mostly affects young adults, with a peak incidence in the 30s. Patients usually present with an asymptomatic swelling commonly affecting the dermis and subcutaneous tissues of the head, neck, and upper extremities. Lower extremities are a much rarer location, and when this occurs, the knee/pretibial region is the most common location. NSM has not been reported within the anterior tibialis muscle. Case Presentation: The authors present the first reported case of NSM in the anterior tibialis muscle in a 39-year-old man presented as deep swelling in the left leg. Discussion: NSM is difficult to diagnose clinically or using standard imaging techniques; MRI and ultrasonography cannot differentiate it from other anomalies. Histopathology alone is not enough to distinguish NSM from neurothekeomas, which were considered synonymous in the past. They can be distinguished by using immunohistochemical markers. Conclusion: Soft tissue tumors in lower extremity muscles are somewhat difficult to diagnose. Excision of the tumor by a specialized orthopedic surgeon and histopathological/immunohistochemical analysis were the only avenues to correctly diagnose the NSM.

Rare forearm intramuscular myxoma: A case report.

Key Clinical Message: Intramuscular myxoma (IMM) is a benign soft tissue tumor of mesenchymal origin that occurs mainly in skeletal muscles which can be removed through surgery after diagnosis. Abstract: Intramuscular myxoma (IMM) is a benign soft tissue tumor of mesenchymal origin that typically occurs in skeletal muscles. Its diagnosis is based on magnetic resonance imaging (MRI) and histopathologic evaluation of the lesion. In our report, we describe the case of a 60-year-old female with an IMM in the supinator muscle of the right forearm, which was confirmed by MRI and histopathologic examination. Following surgery to remove the mass, a follow-up confirmed the patient's recovery and the absence of movement limitations in the elbow joint.

Mazabraud's syndrome: A case report supported by molecular studies and review of the literature.

Mazabraud's syndrome represents rare benign disorder characterized by simultaneous occurrence of fibrous dysplasia of bone and intramuscular myxomas within surrounding soft tissue. Mutations of GNAS1 gene were proven to be causative for this condition. Here, we present a case report of a patient with unusual manifestation of this disease, who developed a pathological fracture of the femur in the setting of monostotic fibrous dysplasia. The intramuscular myxoma of the thigh was discovered during the following orthopedic operation, where the intraoperative diagnosis became a pitfall of the case, as the intramuscular myxoma was initially diagnosed as a low-grade sarcoma from the frozen section. Apart from clinical findings, the diagnosis of Mazabraud's syndrome was further proven by histopathological evaluation and molecular studies of GNAS1 gene. This case raises awareness of such condition as it can easily become a diagnostic pitfall.

Myxoid Soft Tissue Tumors: A 20-Year Experience on Fine Needle Aspiration with Application of the Proposed WHO Reporting System for Soft Tissue Cytopathology.

INTRODUCTION: Myxoid soft tissue tumors represent a heterogenous group of neoplasms. The study presented our experience on cytopathology of myxoid soft tissue tumors on fine needle aspiration (FNA) and aimed to apply the recently proposed WHO system for reporting soft tissue cytopathology. MATERIAL AND METHODS: We performed a 20-year retrospective search of our archives to identify all FNAs performed on myxoid soft tissue lesions. All cases were reviewed, and the WHO reporting system was applied. RESULTS: 129 FNAs performed in 121 patients (62 males; 59 females) showed a prominent myxoid component, accounting for 2.4% of all soft tissue FNAs. The FNAs were performed on 111 (86.7%) primary tumors, 17 (13.2%) recurrent tumors, and one (0.8%) metastatic lesion. A spectrum of non-neoplastic and neoplastic lesions including both benign and malignant neoplasms was identified. Overall, the most common tumors identified were myxoid liposarcoma (27.1%), intramuscular myxoma (15.5%), and myxofibrosarcoma (13.1%). The sensitivity and specificity of FNA regarding the nature of the lesion (benign vs. malignant) were 98% and 100%, respectively. When the WHO reporting system was applied, the frequency of the categories was as follows: benign (7.8%), atypical (34.1%), soft tissue neoplasm of uncertain malignant potential (18.6%), suspicious for malignancy (3.1%), and malignant (36.4%). The risk of malignancy calculated in each category was as follows: benign (10%), atypical (31.8%), soft tissue neoplasm of uncertain malignant potential (50%), suspicious for malignancy (100%), and malignant (100%). CONCLUSION: A diverse group of non-neoplastic and neoplastic lesions can show a prominent myxoid component on FNA. The WHO reporting system for soft tissue cytopathology is easily applicable and appears to correlate well with the malignant potential of myxoid tumors.

Lumbar paraspinal intramuscular myxoma: A case report.

Background: With an estimated incidence of about 1 case/million patients, paravertebral intramuscular myxomas represent a rare cause of lumbar pain. Rather, they typically occur in the heart and in bone tissues. Case Description: A 64-year-old female presented with a protracted course of nocturnal lumbar pain that radiated to the anterior aspect of the right thigh accompanied by numbness. She reported a slow-growing right paramedian lumbar mass in the previous months. The magnetic resonance (MR) showed a right lumbar paravertebral intramuscular mass at the L3 level (i.e., 70 × 50 mm) that had well-defined margins, and markedly enhanced with gadolinium. Following gross total "en bloc" tumor resection, the patient fully recovered. Pathologically, the myofibroblastic lesion proved to be an intramuscular myxoma without malignant changes. Conclusion: A 64-year-old female presented with a slow-growing MR-documented right paramedian lumbar L3 mass responsible for proximal right-thigh numbness. Following "en bloc" gross total removal of the benign intramuscular myxoma, the patient was asymptomatic.

Rare Intramuscular Myxoma Involving the Pterygoid and Masseteric Muscles: A Case Report.

Myxomas, characterized by abundant mucoid stroma and spindle cells, represent a subset of benign soft tissue tumors. Intramuscular myxomas in the maxillofacial region are rare, posing diagnostic challenges. We present the case of a 58-year-old male who reported limited jaw movement. Physical examination revealed asymmetry, restricted mouth opening, and left lateral jaw movement. Imaging confirmed a well-defined myxomatous mass. Core needle biopsy confirmed an intramuscular myxoma involving the pterygoid and masseteric muscles. A multidisciplinary team opted for surveillance due to its benign nature. Follow-up at six months showed stable findings, supporting the decision for non-surgical management. This case highlights the diagnostic and management challenges of rare intramuscular myxomas in the maxillofacial region. A comprehensive diagnostic work-up, including clinical, radiological, and histopathological data, is crucial. Non-surgical management, guided by a benign nature, underscores the importance of judicious and multidisciplinary approaches. Regular follow-up contributes to understanding the natural history of intramuscular myxomas, emphasizing the need for vigilant monitoring in soft tissue tumor management.

Mazabraud's Syndrome.

Teaching point: Mazabraud's Syndrome defines the association of bone fibrous dysplasia and intramuscular myxoma, sometimes with pathological fractures or deformities in the lower limbs.

Diagnostic and Therapeutic Pathways of Intramuscular Myxoma.

Intramuscular myxomas (IMMs) are benign tumors. Evidence regarding diagnostic and therapeutic pathways is rare, and guidelines do not exist due to their low incidence. The aim of this study was a retrospective analysis at a university cancer center and the interdisciplinary re-evaluation of the individual diagnostic and therapeutic procedures. Overall, 38 patients were included in the study. IMMs occurred mostly in middle-aged women. At the time of first consultation, 57.9% had few symptoms or were asymptomatic. In 92.1% of the cases, the tumor was localized in the extremities. The lower extremity was affected in 73.7%. The average size of IMMs was 5.0 cm. The proximally located tumors in the gluteus, thighs, and upper arms were significantly larger (p = 0.02) than the distally-located tumors in the forearms and lower legs. An MRI was performed in 97.4%. Based on imaging, an IMM was suspected in 5.6% by radiologists and in 54.1% by musculoskeletal surgeons. An incision biopsy was performed in 68.4% and led in 100.0% to the right histopathological diagnosis. In total, 89.5% of IMMs were resected. Postoperative complications requiring revision occurred in 8.8%. Recurrences or degenerations of IMMs were not reported in any of these cases.

Unexplained Gait and Balance Changes: A Case Report of Myxoma Mitigation in a Breast Reduction Patient.

In Fall 2020, a female physical therapist (PT) developed mild changes in gait, infrapatellar tendon pain, and lateral patellar tracking. As a PT in good physical condition, she did not access her employer's occupational health clinic but instead she self-treated. Two months after symptom onset and self-treatment, she was diagnosed with an intramuscular myxoma within her left vastus lateralis, the largest muscle within the quadricep. The employee was at risk of slips, trips, and falls as the mass grew. Due to the location and increasing size of the mass, the employee required surgical treatment. Healthcare workers, particularly those who provide treatment, are likely to self-treat rather than seek assistance from the occupational health professional. The employee was seen by a plastic surgeon for an unrelated medical condition which is when the myxoma was diagnosed. Further delay may have led to occupational injury associated with the balance and gait disturbances. Opportunity exists for the occupational health professional to provide a review of services, including screening for musculoskeletal changes associated with occupational injury such as those described herein. This is especially important among those healthcare workers who tend to self-treat.

Incidental Intercostal Intramuscular Myxoma With Fibrous Dysplasia in a Patient With Mazabraud's and McCune Albright Syndromes.

Intramuscular myxoma is a rare entity that may present as single or multiple lesions in patients with Mazabraud's syndrome and is characterized by intramuscular myxomas with fibrous dysplasia. Though intramuscular myxomas occur in large muscle groups, they can very rarely occur in the chest wall. We present the case of a 41-year-old woman with an incidentally discovered intercostal mass on magnetic resonance cholangiopancreatography (MRCP). Repeat MRI demonstrated a lobulated, T2-hyperintense intercostal lesion and demonstrated adjacent fibrous dysplasia of the ribs, consistent with the patient's history of Mazabraud's and McCune Albright syndromes. Histopathological exam following surgical resection confirmed a diagnosis of intramuscular myxoma without the presence of sarcomatous changes. Though small, slow-growing intramuscular myxomas may be observed with conservative management in the absence of significant symptoms, surgical resection is warranted to prevent complications such as osseous erosion or nerve impingement.

Extent of Extraskeletal Manifestations of Fibrous Dysplasia/McCune-Albright Syndrome in Patients with Mazabraud's Syndrome.

Mazabraud's syndrome (MZB) is a rare condition in which fibrous dysplasia of bone/the McCune-Albright syndrome (FD/MAS) co-exists with intramuscular myxomas. Both FD and the myxomas harbor the GNAS-mutation. Recent studies have shown that extraskeletal, GNAS-related features are associated with a more severe phenotype of FD/MAS. However, patients with MZB are often only seen by orthopedic surgeons. We therefore evaluated MZB patients seen in tertiary referral centers from the Netherlands (LUMC), USA (National Institutes of Health) and France (INSERM UMR 1033 (Lyos), Hôpital Edouard Herriot). All FD/MAS patients known in these centers with an additional diagnosis of a myxoma were included. Demographic information and data on disease extent and extraskeletal manifestations of FD/MAS such as precocious puberty (PP) or café-au-lait patches (CAL) were retrieved from patient's medical records. Thirty MZB patients were included: 20 women (67%) and 10 men (33%). Patients received a diagnosis of MZB (median 42 years, range 16-19) significantly later than the diagnosis of FD/MAS (median 30 years, range 0-60), p < 0.01. Twenty-six patients were diagnosed with polyostotic disease (87%). In 97% the myxoma was located near the skeletal FD lesion. The combination of MZB and MAS was made in 13 patients in whom PP (n = 7), CAL (n = 7), GH-excess (n = 3) and hyperthyroidism (n = 3) were present. Other extraskeletal features were (multinodular) goiter (n = 2) and thyroid cysts (n = 1). Furthermore, in this cohort of patients with MZB several (pre-)malignant tumors were observed; ductal carcinoma in situ of the breast in 3 patients (10%), breast cancer in 1 patient (3.3%), intra pancreatic mucinous neoplasms in 3 patients (10%) and liver adenomas in 2 patients (6.6%). A total of 47% of patients with MZB had an additional extraskeletal feature such as an endocrinopathy. In MZB, 87% of patients suffer from polyostotic FD, 43% of patients have extraskeletal GNAS-features such as an hyperfunctioning endocrinopathy and 30% (pre-)malignant tumors. We therefore advocate that MZB patients should undergo a complete screening and long-term follow-up for extent of bone disease, but also extraskeletal GNAS features of FD/MAS.

A case of intramuscular lumbar myxoma: Uncertainty in the preoperative diagnosis of a spinal soft tissue tumour.

We report an uncommon case of a 76-year-old woman who presented with lower back pain, an intermittent L5 radiculopathy and a right palpable paraspinal mass. Imaging studies revealed a 7-cm lumbar paraspinal pseudo-cystic soft tissue tumour developed in the paravertebral musculature, without a clear radiological diagnosis. Gross total surgical resection was performed, resulting in complete resolution of pain. Histopathological studies revealed an intramuscular (IM) myxoma. With a low positive predictive value of radiological work-up and a poor yield of percutaneous biopsies, surgery remains the mainstay treatment for these rare soft tissue tumours of the lumbar spine. Intramuscular myxomas show excellent postoperative results.

Surgical Treatment of Intramuscular Myxoma.

PURPOSE: Intramuscular myxoma (IM) is a rare benign myxoid tumor that may be challenging to differentiate from sarcoma in small amounts of biopsied material. Although IM appears to be well-circumscribed macroscopically, it infiltrates the adjacent edematous muscle microscopically. The recommended treatment is resection, but there is controversy with regard to the appropriate surgical margin. This study aimed to clarify which surgical procedure that should be applied when the preoperative diagnosis is IM and how to manage treatment if the postoperative diagnosis turns out to be a sarcoma. METHODS: We retrospectively examined 55 IM patients treated from January 1982 to December 2014. Patient characteristics, tumor location, tumor size, radiograph, preoperative and postoperative pathological reports, surgical techniques, treatment outcome, and complications were reviewed. The patients were followed up on for at least 5 years. All patients were confirmed not to have Mazabraud syndrome. RESULTS: In the 55 IM patients examined, the mean patient age was 48 years and most were female. The most common tumor locations were in the muscles of the thighs (47%) and buttocks (20%). The mean tumor diameter was 5 cm. Wide resection and marginal resection were performed in 24 and 31 patients, respectively. The mean follow-up duration was 19 years. No local recurrence, malignant transformation, or complications were observed. CONCLUSIONS: Marginal resection is suitable in patients whose preoperative diagnosis is IM, as it is able to prevent local recurrence and allows for the preservation of muscle and muscle fascia. If the postoperative diagnosis turns out to be myxoid sarcoma, minimum surgical contamination makes additional wide resection less invasive.