Mechanisms Underlying the Rarity of Skeletal Muscle Cancers.

Skeletal muscle (SKM), despite comprising ~40% of body mass, rarely manifests cancer. This review explores the mechanisms that help to explain this rarity, including unique SKM architecture and function, which prohibits the development of new cancer as well as negates potential metastasis to SKM. SKM also presents a unique immune environment that may magnify the anti-tumorigenic effect. Moreover, the SKM microenvironment manifests characteristics such as decreased extracellular matrix stiffness and altered lactic acid, pH, and oxygen levels that may interfere with tumor development. SKM also secretes anti-tumorigenic myokines and other molecules. Collectively, these mechanisms help account for the rarity of SKM cancer.

18 F-FAPI-42 Versus 18 F-FDG PET/MRI in a Case of Primary Peripheral T-Cell Lymphoma of the Skeletal Muscles.

ABSTRACT: Primary skeletal muscle lymphoma is rare. We describe 18 F-FAPI-42 and 18 F-FDG PET/MRI findings in a case of primary peripheral T-cell lymphoma of the skeletal muscles with brain involvement. The multiple skeletal muscle tumors and one larger cerebral tumor showed intense FDG uptake and mild to moderate FAPI uptake. FDG PET was superior to FAPI PET in delineating the muscle tumors because of significantly higher FDG uptake of the muscle tumors than FAPI uptake. FAPI PET was superior to FDG PET in delineating the cerebral lesion because of a very low background FAPI activity in the brain parenchyma.

Management of intramuscular melanoma metastases to the psoas.

We detail a case of a woman in her 40s with isolated melanoma skeletal muscle metastasis (MSMM) to the right psoas muscle. This patient underwent R0 surgical resection through a novel pelvic approach. She received subsequent adjuvant immunotherapy with Braftovi/Mektov along with adjuvant radiation. She is currently disease free at 9 months post surgery. Here, we describe our novel surgical approach including description of the tumour pathology. We explain our multidisciplinary management of MSMM consisting of a multidisciplinary surgical approach by surgical oncology, gynecological oncology and urology as well as multidisciplinary medical management by oncology, radiation oncology and pathology. Finally, we discuss best current options for therapeutic management.

Nineteen-Year-Old Woman with Symptomatic Intramuscular Thigh Hemangioma-Radiographic Changes and Management: A Case Report.

CASE: We report a case of an intramuscular thigh hemangioma in a 19-year-old woman with a several year history of atraumatic thigh pain. Radiographs obtained by her primary care physician demonstrated periosteal bone reaction, prompting referral to Orthopaedic Oncology department. The patient had successful symptomatic management with propranolol. CONCLUSION: The case highlights the diagnosis and potential treatments. In a stepwise approach to care for symptomatic benign vascular lesions, propranolol has been a proven therapeutic option and may be a useful first-line therapy for symptomatic hemangiomas.

Management of Diaphragm Tumors.

Diaphragm tumors are very rare, with secondary tumors being more common than primary tumors. The most common benign primary tumors include lipomas and cysts, and malignant primary tumors include rhabdomyosarcoma and leiomyosarcoma. Endometriosis is the most common benign secondary tumor, followed by malignant tumors with localized spread of disease. In addition, widely metastatic disease has been described. Benign lipomas and cysts can be managed conservatively, but more complex or concerning disease typically requires resection. The diaphragm can often be repaired primarily, though any large defect or tension would indicate the need for mesh or an autologous reconstruction.

Cortical hypertrophy in intramuscular hemangioma mimicking bone tumor.

Although hemangiomas are the most common soft tissue tumors, intramuscular hemangiomas account for only 0.8% of all vascular tumors. These lesions are rarely located adjacent to the bone and cause changes in the adjacent bone. They are often mistakenly diagnosed as bone tumors. In this study, a case of a 19-year-old male patient with intramuscular hemangioma causing cortical thickening was reported.

Myositis as a prominent manifestation of primary skeletal muscle peripheral T-cell lymphoma: a case report and literature review.

The patient presented to the clinic with painful muscle swelling in the right lower extremity, which improved with immunosuppressive therapy. Initially, the condition was diagnosed as polymyositis but recurred soon after. After imaging and biopsy, the final diagnosis was primary skeletal muscle peripheral T-cell lymphoma, not otherwise specified (PSM-PTCL, NOS). In this report, we discuss the challenges in diagnosing and treating this aggressive malignancy and review the literature on PSM-PTCL, NOS. Key Points • To date, there are few reports of PSM-PTCL, NOS, and our case is the tenth. • It is crucial to consider PSM-PTCL, NOS, when presenting with localized muscle edema and unexplained pain. • Histopathological examination is likely the most effective method for diagnosing this rare disease.

Intramuscular Granular Cell Tumor Detected on 68 Ga-PSMA PET/CT.

ABSTRACT: Finding of the prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancer (PC) cells that have made it possible to evaluate the patients with PC with a single imaging method. 68 Ga-PSMA PET/CT is now part of the routine in patients with PC. After several years of clinical experience with PSMA tracers, the specificity is satisfactory; however, concerns about the specificity are raising day by day due to the newly laid out nonprostatic malignant and benign lesions with high PSMA expression. Herein, we present an incidental 68 Ga-PSMA uptake in an intramuscular granular cell tumor.

Unique Case of Rare Non-Neural Granular Cell Tumor of the Rectus Abdominis Muscle.

Background and Objectives: Our report contributes a unique case of a non-neural GCT occurring in an unusual location, with its development during pregnancy adding to its rarity. Materials and Methods: Granular cell tumors (GCTs), also known as Abrikossoff's tumors, are rare neoplasms of Schwann cell origin with predominantly benign behavior. We present a case of a 29-year-old female with a non-neural variant of a GCT discovered incidentally during a cesarean section, situated on the posterior surface of the rectus abdominis muscle. Results: Histologically, the tumor exhibited features consistent with a benign non-neural GCT, confirmed through an immunohistochemical analysis. Despite the atypical presentation and challenging surgical removal due to prior scarring, the patient experienced no postoperative complications and showed no signs of recurrence during follow-up. Conclusions: This case highlights the importance of considering GCTs in differential diagnoses, particularly in unusual anatomical locations, and underscores the favorable prognosis associated with timely surgical intervention.

Cardiac and Intramuscular Metastases Following Nephroureterectomy for Metachronous Urothelial Carcinoma.

BACKGROUND We present a case of metachronous cardiac and intramuscular metastases in a patient with a known history of radical nephroureterectomy for upper-tract urothelial carcinoma (UTUC). CASE REPORT A 58-year-old man had a history of metachronous renal pelvis urothelial carcinoma with prior left radical nephroureterectomy. He was also diagnosed with malignancy-associated deep vein thrombosis (DVT) and was on rivaroxaban. He presented at an oncology follow-up consult with shortness of breath and right scapular lump. CT scan revealed a soft-tissue mass at the surgical bed suspicious for local recurrence, as well as intracardiac hypodensities and intramuscular nodules in the right latissimus dorsi and right adductor muscles. The intracardiac hypodensities were located in the left atrial appendage and inter-atrial septum. Given that the patient had a history of DVT and in a pro-thrombotic state, differentials for the intracardiac densities included intracardiac thrombi or metastases. The intramuscular hypodensities were rim-enhancing. Given that the patient was on rivaroxaban, differentials included hematomas or metastases. As there was no overlying bruising and the lesions remained unchanged in size clinically, they were treated as metastases. The patient was treated with clexane but re-presented with worsening of shortness of breath and palpitations. CT scan showed increased size of intracardiac lesions, suggesting no response to anticoagulation, and therefore were likely metastatic in nature. He completed a 2-year course of IV pembrolizumab and was in complete remission. CONCLUSIONS Our case highlights the importance of this clinically challenging scenario when patients with known malignancy and on anticoagulation present with cardiac or musculoskeletal symptoms. Though these patients are at risk of thrombus and haematoma, cardiac and intramuscular metastasis should be considered, as the prognosis is guarded.

Advancing musculoskeletal tumor diagnosis: Automated segmentation and predictive classification using deep learning and radiomics.

OBJECTIVES: Musculoskeletal (MSK) tumors, given their high mortality rate and heterogeneity, necessitate precise examination and diagnosis to guide clinical treatment effectively. Magnetic resonance imaging (MRI) is pivotal in detecting MSK tumors, as it offers exceptional image contrast between bone and soft tissue. This study aims to enhance the speed of detection and the diagnostic accuracy of MSK tumors through automated segmentation and grading utilizing MRI. MATERIALS AND METHODS: The research included 170 patients (mean age, 58 years ±12 (standard deviation), 84 men) with MSK lesions, who underwent MRI scans from April 2021 to May 2023. We proposed a deep learning (DL) segmentation model MSAPN based on multi-scale attention and pixel-level reconstruction, and compared it with existing algorithms. Using MSAPN-segmented lesions to extract their radiomic features for the benign and malignant classification of tumors. RESULTS: Compared to the most advanced segmentation algorithms, MSAPN demonstrates better performance. The Dice similarity coefficients (DSC) are 0.871 and 0.815 in the testing set and independent validation set, respectively. The radiomics model for classifying benign and malignant lesions achieves an accuracy of 0.890. Moreover, there is no statistically significant difference between the radiomics model based on manual segmentation and MSAPN segmentation. CONCLUSION: This research contributes to the advancement of MSK tumor diagnosis through automated segmentation and predictive classification. The integration of DL algorithms and radiomics shows promising results, and the visualization analysis of feature maps enhances clinical interpretability.

Recurrent Metastatic Ewing Sarcoma Involving Only in the Muscles of Extremities Shown on FDG PET/CT.

ABSTRACT: Ewing sarcoma is the second most common osseous malignancy in pediatric patient. Metastasis is common due to its aggressive nature, with 25% of patients with metastasis at diagnosis, commonly to the lungs, bone, or bone marrow. Muscle metastasis is uncommon. We report FDG PET/CT findings of multifocal muscle metastases of recurrent Ewing sarcoma in the extremities without lung and bone involvement in a 6-year-old boy.

Multispecialty Management of Metastatic Colon Adenocarcinoma Involving the Extraocular Muscles: Primary Excision and Simultaneous Treatment of Strabismus With a Review of the Literature.

Metastatic colon adenocarcinoma involving the extraocular muscles is extremely rare. It usually develops following the diagnosis of the systemic disease and therefore, management and treatment require a multispecialty approach. Within this manuscript, we provide a summary of cases of orbital metastasis secondary to colon cancer. We further discuss a detailed case of a 42-year-old male patient who developed recent-onset diplopia in the left gaze. Orbital CT imaging showed a localized, well-circumscribed enlargement of the right medial rectus muscle. The biopsy of the right medial rectus showed adenocarcinoma originating from the gastrointestinal system. Further workup revealed colon adenocarcinoma with multiple metastatic sites. The patient started systemic chemotherapy. After 2 months of chemotherapy (5-fluouracil, oxaliplatin, irinotecan, and leucovorin), all systemic metastatic sites regressed; however, his medial rectus muscle continued to grow, causing compressive optic neuropathy. The patient underwent excisional biopsy of the right medial rectus muscle with simultaneous repair of the strabismus with transposition of superior and inferior recti muscles. He continued with systemic chemotherapy. Follow up in 1 year revealed no local orbital tumor recurrence with excellent visual acuity and no diplopia in primary gaze.

Giant orbital leiomyoma in a pediatric patient: diagnostic and therapeutic challenge.

This manuscript describes an exceptional case of a long-standing orbital leiomyoma in a 14-year-old male. The tumor was unusually large, causing severe proptosis and significant involvement of the ocular muscles. The patient presented with amaurosis, complete ophthalmoplegia, spontaneous eye pain, and the inability to close the eyelids, leading to psychological distress. Due to the tumor's size and progression, a right orbital exenteration was performed to remove all orbital contents, including the tumor and the eyeball. The surgical procedure aimed to prevent tumor recurrence and improve the patient's quality of life. The histopathological analysis confirmed the diagnosis of orbital leiomyoma. This case presents a particular interest due to the degree of evolution it has reached. Complete tumor excision and long-term follow-up are necessary to prevent recurrence and ensure optimal patient outcomes. This report underscores global healthcare disparities and the complexity of managing rare orbital neoplasms in diverse country settings.

Rapidly growing intramuscular lipoma: a unique entity of benign lipomas in children.

This report presents a case of an intramuscular lipoma observed in the left back of a healthy female toddler. It was resected after 3 months of observation because of rapid enlargement, raising suspicion of malignancy. Histopathological examination confirmed a diagnosis of intramuscular lipoma without malignant and blastemal components. Intramuscular lipomas are benign neoplasms that mostly appear as a rapidly growing tumour. Several hypotheses regarding the pathogenesis of this characteristic growth pattern have been proposed, including atrophy of the surrounding muscle, reactive adipocytic neoformation and multiple contractive interactions between the lipoma and the surrounding muscle.

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.

Inflammatory Rhabdomyoblastic Tumor: From a Nebulous Smooth Muscle Neoplasm to a Novel Skeletal Muscle Tumor Subtype.

Inflammatory rhabdomyoblastic tumor is a recently introduced name for neoplasms currently included in the World Health Organization classification of soft tissue tumors under the rubric inflammatory leiomyosarcoma. Inflammatory rhabdomyoblastic tumor is an excellent example of how surgical pathologists working in conjunction with tumor biologists can greatly improve tumor classification to the benefit of patients. Over the last 28 years, understanding of this entity has undergone a fascinating evolution. This review serves as a summary of the latest findings in inflammatory rhabdomyoblastic tumor research and a diagnostic manual for the practicing surgical pathologist.

Inflammatory Rhabdomyoblastic Tumor: Clinicopathologic and Molecular Analysis of 13 Cases.

Inflammatory rhabdomyoblastic tumors (IRMTs) are newly recognized skeletal muscle tumors with uncertain malignant potential. We investigated 13 IRMTs using clinicopathologic, genetic, and epigenetic methods. The cohort included 7 men and 6 women, aged 23 to 80 years (median, 50 years), of whom 2 had neurofibromatosis type 1. Most tumors occurred in the deep soft tissues of the lower limbs, head/neck, trunk wall, and retroperitoneum/pelvis. Two tumors involved the hypopharyngeal submucosa as polypoid masses. Eight tumors showed conventional histology of predominantly spindled cells with nuclear atypia, low mitotic activity, and massive inflammatory infiltrates. Three tumors showed atypical histology, including uniform epithelioid or plump cells and mitotically active histiocytes. The remaining 2 tumors demonstrated malignant progression to rhabdomyosarcoma; one had additional IRMT histology and the other was a pure sarcoma. All 11 IRMTs without malignant progression exhibited indolent behavior at a median follow-up of 43 months. One of the 2 patients with IRMTs with malignant progression died of lung metastases. All IRMTs were positive for desmin and PAX7, whereas myogenin and MyoD1 were expressed in a subset of cases. Targeted next-generation sequencing identified pathogenic mutations in NF1 (5/8) and TP53 (4/8). All TP53 mutations co-occurred with NF1 mutations. TP53 variant allele frequency was much lower than that of NF1 in 2 cases. These tumors showed geographic (subclonal) strong p53 immunoreactivity, suggesting the secondary emergence of a TP53-mutant clone. DNA methylation-based copy number analysis conducted in 11 tumors revealed characteristic flat patterns with relative gains, including chromosomes 5, 18, 20, 21, and/or 22 in most cases. Widespread loss of heterozygosity with retained biparental copies of these chromosomes was confirmed in 4 tumors analyzed via allele-specific profiling. Based on unsupervised DNA methylation analysis, none of the 11 tumors tested clustered with existing reference entities but formed a coherent group, although its specificity warrants further study.