FDG PET/CT and MR imaging of intramuscular myxoma in the gluteus maximus

Superficial Angiomyxoma of the Wrist: Case Report and Literature Review

BACKGROUND/AIM

Superficial angiomyxoma (SAM) is a rare benign soft-tissue tumor that usually occurs in the trunk, head and neck, and lower extremity of middle-aged adults. Herein, we describe an unusual case of SAM of the wrist, which was initially diagnosed as a ganglion cyst on imaging.

CASE REPORT

The patient was a 71-year-old man with no history of trauma who presented with a 2-year history of a palpable mass in the left wrist. Physical examination revealed a 2.5-cm, elastic hard, mobile, nontender mass. Magnetic resonance imaging revealed a well-defined mass with iso-signal intensity relative to skeletal muscle on T1-weighted sequences and very high signal intensity on T2-weighted fat-suppressed sequences. Subtle internal enhancement was seen following gadolinium administration. Complete excision was performed under general anesthesia with tourniquet control. Histologically, the lesion was composed of bland spindle to stellate-shaped cells in an abundant myxoid stroma. Immunohistochemically, the lesional cells were positive for CD34 but negative for S-100 protein, smooth-muscle actin, desmin, epithelial membrane antigen and pancytokeratin. These findings were consistent with a diagnosis of SAM. There was no clinical evidence of recurrence during a follow-up period of 3 months.

CONCLUSION

Although extremely rare, SAM should be considered in the differential diagnosis of a cyst-like solid lesion near small joints.

Imaging manifestations and pathological analysis of intramuscular myxoma: A case report and literature review

Intramuscular Myxoma(IM) is a rare benign soft tissue tumor, and its etiology and histology source is still unclear. It is important to understand the pathological components of IM and its corresponding imaging features, as well as performing accurate and careful imaging assessments of IM before surgery. We present a case of a 43-year-old male who presented a lump in his left thigh and gradually enlarged during the past 8 years. The patient underwent CT, MRI, and CTA examined and was later pathologically confirmed as IM. This article will combine the literature，to explore the imaging manifestations and its pathological basis of intramuscular myxoma.

Diagnostic value of ultrasonography and other imaging examinations in patients with intramuscular myxoma: A case series and literature review

Intramuscular myxoma (IM) is a rare benign soft tumor of mesenchymal origin. Most IMs are located in the large skeletal muscles, and they are typically painless slow-growing masses that are detected incidentally. Surgical excision of IM usually has a good prognosis. Because of its rarity, diagnosing IM via imaging modalities such as ultrasonography (US), computed tomography, positron emission tomography/computed tomography, and magnetic resonance imaging (MRI) can be challenging. Relevant literature and cases were selected as per the inclusion and exclusion criteria. Characteristic imaging findings include a well-defined, ovoid mass with regular morphology and an orientation whereby the long axis is aligned with the course of muscle fibers. In US, IMs exhibit solid cystic mixed echo without obvious blood flow signal. However, MRI reveals hypointensity on T1-weighted images and hyperintensity on T2-weighted images with mild and patchy enhancement. In cases of suspected or potential IM, US and MRI can provide excellent resolution at a reasonable cost. This report aims to improve the recognition rate of IM. Herein, we review imaging characteristics that can contribute to the differential diagnosis of IM.

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.

Juxta-articular Myxoma of the Hip: A Rare Pediatric Tumor

Juxta-articular myxoma (JAM) is a very rare myxoid tumor in pediatric age. JAM is frequently located at large joints, particularly in the knee, and most lesions present as palpable swelling sometimes associated with pain or tenderness. Only three cases of pediatric JAM have been reported in the literature to date. We describe a case of JAM in a 12-year-old boy, characterized by several unique aspects related to age, site of onset, size, and associated symptoms.

Radiomic features from MRI distinguish myxomas from myxofibrosarcomas

BACKGROUND

Myxoid tumors pose diagnostic challenges for radiologists and pathologists. All myxoid tumors can be differentiated from each other using fluorescent in-situ hybridization (FISH) or immunohistochemical markers, except for myxomas and myxofibrosarcomas. Myxomas and myxofibrosarcomas are rare tumors. Myxomas are benign and histologically bland, whereas myxofibrosarcomas are malignant and histologically heterogenous. Because of the histological heterogeneity, low grade myxofibrosarcomas may be mistaken for myxomas on core needle biopsies. We evaluated the performance of T1-weighted signal intensity (T1SI), tumor volume, and radiomic features extracted from magnetic resonance imaging (MRI) to differentiate myxomas from myxofibrosarcomas.

METHODS

The MRIs of 56 patients (29 with myxomas, 27 with myxofibrosarcomas) were analyzed. We extracted 89 radiomic features. Random forests based classifiers using the T1SI, volume features, and radiomic features were used to differentiate myxomas from myxofibrosarcomas. The classifiers were validated using a leave-one-out cross-validation. The performances of the classifiers were then compared.

RESULTS

Myxomas had lower normalized T1SI than myxofibrosaromas (p = 0.006) and the AUC using the T1SI was 0.713. However, the classification model using radiomic features had an AUC of 0.885 (accuracy = 0.839, sensitivity = 0.852, specificity = 0.828), and outperformed the classification models using T1SI (AUC = 0.713) and tumor volume (AUC = 0.838). The classification model using radiomic features was significantly better than the classifier using T1SI values (p = 0.039).

CONCLUSIONS

Myxofibrosarcomas are on average higher in T1-weighted signal intensity than myxomas. Myxofibrosarcomas are larger and have shape differences compared to myxomas. Radiomic features performed best for differentiating myxomas from myxofibrosarcomas compared to T1-weighted signal intensity and tumor volume features.

18F-FDG PET/CT and MRI features of myxoid liposarcomas and intramuscular myxomas

OBJECTIVE

To examine the imaging characteristics of intramuscular myxomas (IM) and myxoid liposarcomas (MLS) on ¹⁸F-FDG PET/CT and MRI.

MATERIALS AND METHODS

With IRB approval, our institutional imaging database was searched for pathologically proven IM and MLS evaluated by ¹⁸F-FDG PET/CT and MRI. PET/CT and MRI imaging characteristics were recorded and correlated with pathologic diagnosis.

RESULTS

We found eight patients (2 M, 6 F) with IM (mean age 65.6 ± 10.4 years) and 16 patients (7 F, 9 M) with MLS (mean age 42.8 ± 16.3 years). MRI was available in 7/8 IM and 15/16 MLS patients. There was no significant difference between the two groups in SUVmax (IM 2.7 ± 0.8, MLS 3.0 ± 1.0; p = 0.35), SUVmean (1.7 ± 0.4, 1.5 ± 0.5; p = 0.40), total lesion glycolysis (101.8 ± 127.3, 2420.2 ± 4003.3 cm³*g/ml; p = 0.12), metabolic tumor volume (62.3 ± 71.1, 1742.9 ± 3308.0 cm³; p = 0.17) or CT attenuation (p = 0.70). MLS occurred in younger patients (p = 0.0015), were larger (16.4 ± 8.2 vs. 5.6 ± 2.5 cm; p = 0.0015), more often T1 hyperintense (p = 0.03), with nodular enhancement (p = 0.006), and macroscopic fat on CT (p = 0.0013) and MRI (p = < 0.001) compared to myxomas.

CONCLUSIONS

IM and MLS most commonly demonstrate low-grade FDG activity and overlapping metabolic measures on PET/CT. MRI is useful in differentiation, but MLS can present without macroscopic fat on MRI, underscoring the importance of radiologic-pathologic correlation for accurate diagnosis.

Musculoskeletal Pitfalls on Fluorodeoxyglucose F 18 PET-Computed Tomography: Pictorial Review

A wide range of musculoskeletal processes can demonstrate increased uptake on PET-computed tomography (CT) with fluorodeoxyglucose (FDG) F 18, including reactive, benign neoplastic, inflammatory, traumatic, posttreatment, and arthritic conditions that may mimic malignancy. In addition, physiologic causes of increased FDG uptake such as asymmetric muscle use and presence of brown fat can lead to increased FDG uptake and potential false-positive results. This article presents various case examples of non-malignant musculoskeletal hypermetabolism on 18F-FDG PET-CT and describes useful tools to avoid the potential pitfall of misinterpreting these as malignancy.

[Imaging characteristics of malignant and benign lesions of skeletal muscle]

There are many different tumors and tumor-like lesions with variable biological behavior that may affect the skeletal musculature. The aim of this study was to review the different intramuscular lesions and to provide a classification based on their radiological patterns. Intramuscular lesions can present as solid, liquid, semiliquid or fat equivalent manifestations and also as diffuse muscle enlargement and muscle calcification. Additionally, lesions with mixed patterns of the aforementioned alterations can also occur. Benign and malignant muscle lesions can often manifest with identical radiological patterns, which is why a certain differentiation is often difficult. A systematic radiological description and when possible assignment with respect to etiology and dignity depending on the patient history is necessary in order to recommend a subsequent histological confirmation or to avoid unnecessary confirmation.

Multiple and solitary skeletal muscle metastases on 18F-FDG PET/CT imaging

OBJECTIVE

The aim of this study was to investigate the features and patterns of skeletal muscle metastases (SMM) detected with F-fluorodeoxyglucose (F-FDG) PET/computed tomography (PET/CT).

PARTICIPANTS AND METHODS

Our database was analyzed for patients with pathologically proven malignancy, who underwent F-FDG PET/CT in our institution. The patients with SMM were included in the study group on the basis of the final diagnosis confirmed by follow-up or histopathology. Images were acquired using a PET/CT system Biograph mCT S(64)-4R. CT was performed without contrast enhancement.

RESULTS

The selected group included 31 patients (1.7% of the database, which consisted of 1805 patients). A total of 233 lesions were found. The prevalence of SMM evaluated in specific primary malignancies was the highest in melanoma (6.9%), followed by carcinoma of unknown primary (4.4%), colorectal cancer (4.1%) and lung cancer (2.8%). Three patterns of skeletal muscle metastatic involvement were observed: multiple SMM accompanied by other metastases (64.5%), solitary lesion associated with other metastases (29%) and isolated intramuscular lesions (two cases, 6.5%). Isolated SMM represented recurrence of the malignant disease. In patients with extraskeletal metastases, solitary or multiple SMM did not affect tumor staging.

CONCLUSION

Solitary SMM are less common than multiple on F-FDG PET/CT imaging. SMM are usually associated with other metastases and do not affect tumor staging. The cases of isolated SMM are very rare. Nevertheless, in patients with a diagnosis of malignant disease, a solitary, F-FDG avid intramuscular focus should be suspected to represent metastasis.

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.

Malignant and benign lesions of the skeletal musculature

There are several tumors and tumorlike conditions with variable biological behavior that may involve the skeletal musculature. The aim of this work was to review different intramuscular lesions and to provide a classification of muscle lesions based on their radiological patterns as well as to provide as a pictorial essay the imaging characteristics of typical muscle lesions. Radiologically, intramuscular lesions can manifest as solid masses, liquid or semiliquid masses, fat-containing lesions, diffuse muscle enlargement, and muscle calcifications. Additionally, lesions with mixed patterns can also occur. It is noteworthy that different malignant or benign muscle lesions can manifest with identical radiological patterns.

Intramuscular myxoma of the buttock mimicking low-grade fibromyxoid sarcoma: diagnostic usefulness of MUC4 expression

Intramuscular myxoma (IM) is a benign intramuscular neoplasm composed of fibroblasts and abundant myxoid stroma. Some malignant soft tissue tumors can undergo myxomatous degeneration, which makes it difficult to distinguish them from IM. We describe a case of IM of the buttock region mimicking low-grade fibromyxoid sarcoma. The tumor appeared as a well-defined ovoid mass with a cystic lesion on MRI images, and mild uptake on PET images was seen. This was originally misdiagnosed as low-grade fibromyxoid sarcoma (LGFMS) after core-needle biopsy. The mass was excised en bloc and sent for histology. The surgical specimen showed the features of LGFMS with the same characteristics as those mentioned in the previous biopsy report. After surgery, MUC4 expression, a highly sensitive and specific immunohistochemical marker for LGFMS, and FUS gene rearrangement by FISH was not detected upon re-examination; therefore, a conclusive diagnosis of IM was made. The patient had no local recurrence at the 3-year follow-up. Our case suggests that IM with mild FDG uptake is frequently confused with other low-grade malignant myxoid tumors. In addition, absence of MUC4 expression is the definitive key to distinguish IM from LGFMS.

Intramuscular myxoma in the chest wall

Intramuscular myxomas are benign soft-tissue tumors that often develop in the thigh. A 66-year-old woman was referred with an abnormal shadow on chest roentgenogram. The tumor was well defined and smooth and originated from the second intercostal space. Positron emission tomography showed no accumulation of 18F-fluorodeoxyglucose in the tumor. The patient attended the outpatient department for follow-up care. Because the mass grew slightly after 52 months, the patient underwent complete removal by video-assisted thoracoscopic surgery. On histopathological examination, the tumor was diagnosed as an intramuscular myxoma in the chest wall. The patient has had no recurrence 3 years after surgery. A case of intramuscular myxoma in the chest wall, completely resected by video-assisted thoracoscopic surgery, is reported. A well-defined, smooth, homogeneous mass in the chest wall may therefore be intramuscular myxoma.