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.

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.

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.

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.

Giant Intramuscular Myxoma of Thigh- A Rare Case Report

INTRODUCTION

Myxoid soft tissue tumors consist of a heterogeneous group of mesenchymal neoplasms with a hallmark of the abundant extracellular myxoid matrix. Intramuscular myxomas are rare benign tumor affecting the musculoskeletal system. The common sites include the thigh, upper arm, calf, and the buttocks. Magnetic resonance imaging is the radiological modality of choice in diagnosing these cases, while tissue biopsy is the gold standard.

CASE PRESENTATION

A 70-year-old male presented to orthopedics out-patient department with complaints of a humongous swelling engulfing his right thigh all around. The gradual and progressive appearance of burning sensations and rest pain around the affected area with difficulty in bearing weight, over the past 6-7 months forced him to seek medical attention. Biopsy and imaging were performed followed by final excision. The tumor was removed En-bloc and post-operative period was uneventful. The patient did not show any signs recurrence and was asymptomatic until the final followup of 26 months.

CONCLUSION

Myxomatous swelling mimics an intramuscular lipoma, sarcoma, hematoma, or a hemangioma and must be carefully evaluated. En-bloc excision without spillage is the treatment of choice which ensures long and lasting recovery.

Intramuscular myxoma of the deltoid muscle in a swimmer: A rare case report and literature review

Intramuscular myxoma (IM) is a rare mesenchymal neoplasm with the incidence of one per 1 000 000 people and is reported greater among women. Our case reports an IM of a deltoid muscle in a young man. Differential diagnosis with sarcoma is important. Surgery is the treatment of choice usually without recurrence.

Multiple paraspinal intramuscular myxomas: case report

Intramuscular myxomas (IMMs) are rare benign tumors of mesenchymal origin that are most often located in large skeletal muscles, particularly of the thigh. They have also been reported within the paraspinal musculature and should be considered in the differential diagnosis of a paraspinal mass. These lesions can cause neurological symptoms due to mass effect. This is a report of a 52-year-old man with multiple paraspinal tumors that exhibited concerning growth on serial imaging studies. To the authors' knowledge, this represents the first report of a patient with multiple paraspinal myxomas. CT-guided biopsy followed by surgical excision of the largest mass was performed. Histopathological analysis was consistent with an IMM. Patients with multiple IMMs often have an underlying genetic syndrome such as Mazabraud syndrome, McCune-Albright syndrome, or Carney complex. Despite variable growth patterns and associations with genetic syndromes, multiple IMMs have had no documented cases of malignant transformation into myxoid sarcoma; therefore, surgical excision should be considered based on a patient's individual symptoms.

Mazabraud's Syndrome: A Case Report and Up-To-Date Literature Review

OBJECTIVE

Mazabraud's syndrome is a rare form of bone fibrous dysplasia associated with intramuscular myxomas. Fibrous dysplasia, is generally localized to pelvis and femur and it results in a fragile bone with deformities, pain, pathological fractures and functional impairment. Intramuscular myxomas, are rare benign mesenchymal neoplasms that exceptionally may evolve to malignant forms.

METHODS

This case report describes a 66-year-old woman with Mazabraud's Syndrome (MS), characterized both by monostotic right femur fibrous dysplasia and by a solitary intramuscular myxoma at the right quadriceps muscle, that underwent a long-term treatment (4 years) with intravenous zoledronic acid.

RESULTS

Zoledronic acid therapy rapidly lowered bone pain together with a reduction of intramuscular myxoma volume, but did not affect the extension of fibrous dysplasia. No adverse effects have been observed during treatment.

CONCLUSION

Highly active bisphosphonates are commonly used for the treatment of bone metabolic disorders and they are generally well tolerated. Zoledronic acid may represent a promising alternative to surgical intervention in MS, although its use in rare form of bone fibrous dysplasias is still controversial.

Non-small cell lung cancer with concomitant intramuscular myxoma of the right psoas mimicking intramuscular metastasis: A case report and literature review

Intramuscular myxoma (IMM) as a rare soft-tissue tumor arising from the muscles is completely benign. When IMM accompanies malignance, it may be misdiagnosed as muscle metastasis, and for this extremely rare concurrence, the subsequent treatment would vary accordingly. The current study presents, to the best of our knowledge, the first case of non-small cell lung cancer (NSCLC) concomitant with IMM mimicking skeletal muscle metastasis. A 64-year-old female was hospitalized with a history of chest discomfort and right lumbar pain that had persisted for four months. The computed tomography scan showed a lesion in the left upper lobe of the lung and the right psoas, respectively. Serum biomarkers for NSCLC were abnormal. A presumptive clinical diagnosis was compatible with left NSCLC and right psoas muscle metastasis (cT2aN3M1b, stage IV). Stage IV lung cancer would receive palliative treatment. However, the final diagnosis of synchronous left lung squamous cell carcinoma (cT2aN3M0, stage IIIB) and IMM in the right psoas was confirmed by biopsy. The patient therefore underwent definitive chemoradiotherapy for lung carcinoma, and conservative treatment, including analgesics, for IMM. The diagnosis process for a malignant neoplasm concomitant with IMM is not straightforward due to a lack of clinical experience, and it significantly affects the tumor staging and subsequent treatment strategy. The present case suggests that IMM should be included in the differential diagnosis when an abnormal intramuscular lesion concomitant with malignancy is identified. The value of histopathological diagnosis prior to definitive treatment also requires highlighting.

Fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography in evaluation of residual intramuscular myxoma

Intramuscular myxoma (IM) is a rare benign neoplasm. In a patient diagnosed with IM of left thigh, we report the utility of a postoperative fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography scan in assessing the efficacy of surgical excision.

Sonographic appearance of an intramuscular myxoma of the pectoralis major muscle

Intramuscular myxomas are benign soft tissue tumors that usually involve skeletal muscle of the extremities; occurrence in the chest wall is extremely rare. We describe a case of intramuscular myxoma in the pectoralis major muscle of a 55-year-old woman. The patient presented with a palpable lump in her right breast. Mammography showed a circumscribed, oval, hyperdense mass within the pectoralis muscle. Ultrasonography showed a circumscribed, oval, complex mass within the pectoralis muscle.

Intramuscular myxoma of the hyoglossus muscle: A case report and literature review

Intramuscular myxoma (IM) is a benign intramuscular neoplasm composed of fibroblasts and abundant myxoid stroma. IMs most commonly affect larger skeletal muscles, while those affecting the oral and maxillofacial regions are rare, with a small number of documented cases in the available literature. The aim of the present study was to describe a highly rare case of an IM within the hyoglossus muscle of the tongue in a 74-year-old male. The patient presented with a painless mass in the submental space that had been growing slowly for more than five years. A computed tomography scan revealed a hypodense lesion located in the root of the tongue. The mass was easily excised with thin margins, including only a small amount of the adjacent muscle tissue. The pathological diagnosis of the mass was an IM. The patient made an excellent recovery following the surgery and the follow-up three years later revealed no local recurrence. IMs of the hyoglossus muscle are highly rare, however must be considered in the differential diagnosis of swellings in the root of the tongue region.

Mazabraud syndrome

A 25 year old lady presented with pain and swelling of left thigh. On examination she was found to have tenderness of left femur with a separate soft tissue swelling within the thigh muscle. Further evaluation revealed expansile bony lesion on X-ray of left tibia and multiple hot spots on bone scan suggestive of fibrous dysplasia. The soft tissue swelling on excision and histopathological examination was found to be intramuscular myxoma. The combination of the above two, called Mazabraud syndrome is being reported.

Cellular myxoma of the lumbar spine

BACKGROUND

Cellular myxoma is a histopathologically distinctive benign neoplasm, which has often been categorized among the broad category of benign mesenchymal tumors with myxoid stroma and fibroblast- and/or myofibroblast-like cells. These tumors can arise in any of the large muscles and are usually found in the thigh, shoulder, buttocks, and upper arm, and more rarely in the head and neck or in small muscles of the hand.

CASE DESCRIPTION

Here we illustrate the case of a 57-year-old female with a spinal lesion, who initially presented with complaints of vague pelvic discomfort but no focal neurological deficits. Imaging revealed a sharply demarcated paraspinal lesion concerning for a tumorous growth. The lesion was excised in toto and a detailed immuno-histopathological analysis was performed revealing the diagnosis of a cellular myxoma. Postoperative imaging showed a gross total resection and the patient is under clinical surveillance since, with no signs of recurrence after 42 months.

CONCLUSION

Although very rare, this entity should be considered in the differential diagnosis of any spinal and paraspinal mass to allow for adequate treatment, which requires wide excision with clean margins to avoid any local recurrence.