An Integrative Morphologic and Molecular Approach for Diagnosis of Rhabdomyosarcoma and Subclassification of Rhabdomyosarcoma

Anlotinib treatment for rapidly progressing pediatric embryonal rhabdomyosarcoma in the maxillary gingiva: a case report

BACKGROUND

Embryonal rhabdomyosarcoma (ERMS) is a highly aggressive form of soft-tissue sarcoma that predominantly affects children. Due to limited benefits and resistance to therapy, there is an unmet need to explore alternative therapeutic strategies.

CASE PRESENTATION

In this report, we present a rare case of pediatric ERMS located on the right side of the maxillary gingiva. A composite reference guide integrating clinical, radiographic, and histopathologic findings was used for a definitive diagnosis. Targeted next-generation sequencing of tumor biopsy was performed to identify genetic alterations. A 12-year-old female was admitted to the Pediatric Intensive Care Unit (PICU) and underwent a tracheotomy to relieve asphyxiation caused by a 5.5 cm diameter mass compressing the tongue root and pharyngeal cavity. Hematoxylin and eosin staining revealed a hybrid morphology characterized by clusters of round and spindle cells. Further immunohistochemistry assays indicated positive immunoreactivity for desmin, myogenin, and MyoD1. Various genetic alterations were identified, including mutations in GNAS, HRAS, LRP1B, amplification of MDM2 and IGF1R, and two novel IGF1R fusions. Negative PAX-FOXO1 fusion status supported the clinical diagnosis of ERMS. Initial treatment involved standard chemotherapy; however, the tumor persisted in its growth, reaching a maximum volume of 12 cm × 6 cm × 4 cm by the completion of treatment. Subsequent oral administration of anlotinib yielded a significant antitumor response, characterized by substantial tumor necrosis and size reduction. Following the ligation of the tumor pedicle and its removal, the patient developed a stabilized condition and was successfully discharged from PICU.

CONCLUSIONS

Our study highlights the importance of accurate diagnosis established on multifaceted assessment for the effective treatment of ERMS. We present compelling evidence supporting the clinical use of anlotinib as a promising treatment strategy for pediatric ERMS patients, especially for those resistant to conventional chemotherapy.

Disseminated pleomorphic rhabdomyosarcoma in a horse

An 8-y-old National Show Horse mare was presented for evaluation of pneumonia and laminitis. Harsh bronchovesicular sounds were auscultated throughout both lung fields, and the mare had signs of moderately painful laminitis. Thoracic ultrasonography revealed lung consolidation throughout the dorsal aspect of both lungs, and radiography revealed an extensive diffuse-to-patchy bronchointerstitial lung pattern. The mare's clinical condition rapidly deteriorated, and euthanasia was elected. On postmortem examination, the lungs, omentum, spleen, liver, adrenal glands, kidneys, and femur contained 0.5-2.5-cm, firm, tan nodules. Histologically, the lungs, spleen, liver, kidneys, adrenal glands, omentum, left eye, and femur were infiltrated by bundles and nests of pleomorphic polygonal-to-spindloid cells intermixed with frequent multinucleate cells. Lymphatic vessels in the affected tissues were frequently distended with tumor emboli. Neoplastic cells were diffusely positive for vimentin, desmin, sarcomeric actin, myoblastic differentiation protein 1, and myogenin, supportive of the diagnosis of rhabdomyosarcoma (RMS), which is a rare neoplasm in horses. Cross-striations were not evident with H&E or phosphotungstic acid-hematoxylin stains. Markedly pleomorphic neoplastic cells, multinucleate cells, and lack of cross-striations suggested the subclassification of pleomorphic RMS.

Limonoids isolated from Chisocheton ceramicus Miq. and the antiadipogenic mechanism of action of ceramicine B

Different types of limonoids have been isolated from plants of the Chisocheton genus, notably from the species Chisocheton ceramicus Miq. which is largely distributed in the Indonesian archipelago and Malaysia region. A variety of natural products have been found in the bark of the tree and characterized as antimicrobial and/or antiproliferative agents. The isolated limonoids include chisomicines A-E, proceranolide, and a few other compounds. A focus is made on a large series of limonoids designated ceramicines A to Z including derivatives with antiparasitic activities, antioxidant, antimelanogenic, and antiproliferative effects and/or acting as regulators of lipogenesis. The lead compound in the series is ceramicine B functioning as a potent inhibitor of lipid droplet accumulation (LDA). Extracts from Chisocheton ceramicus and ceramicines have shown anti-LDA effects, with little or no cytotoxic effects. Ceramicine B is the most active compound functioning as a regulator of lipid storage in cells and tissues. Ceramicine B is a transcriptional repressor of peroxisome proliferator-activated receptor γ (PPARγ) and an inhibitor of phosphorylation of the transcription factor FoxO1, acting via an upstream molecular target. Targeting of glycogen synthase kinase-3β is proposed, based on the analogy with structurally related limonoids known to target this enzyme, and supported by a molecular docking analysis. The target and pathway implicated in ceramicine B activity are discussed. The analysis shed light on ceramicine B as a natural product precursor for the design of novel compounds capable of reducing LDA in cells and of potential interest for the treatment of obesity, liver diseases, and other pathologies.

Histogram Analysis of Apparent Diffusion Coefficient Maps Provides Genotypic and Pretreatment Phenotypic Information in Pediatric and Young Adult Rhabdomyosarcoma

INTRODUCTION

We evaluate the role of apparent diffusion coefficient (ADC) histogram metrics in stratifying pediatric and young adult rhabdomyosarcomas.

METHODS

We retrospectively evaluated baseline diffusion-weighted imaging (DWI) from 38 patients with rhabdomyosarcomas (Not otherwise specified: 2; Embryonal: 21; Spindle Cell: 2; Alveolar: 13, mean ± std dev age: 8.1 ± 7.76 years). The diffusion images were obtained on a wide range of 1.5 T and 3 T scanners at multiple sites. FOXO1 fusion status was available for 35 patients, nine of whom harbored the fusion. 13 patients were TNM stage 1, eight had stage 2 disease, nine were stage 3, and eight had stage 4 disease. 23 patients belonged to Clinical Group III and seven to Group IV, while two and five were CG I and II, respectively. Nine patients were classified as low risk, while 21 and five were classified as intermediate and high risk respectively. Histogram parameters of the apparent diffusion coefficient (ADC) map from the entire tumor were obtained based on manual tumor contouring. A two-tailed Mann-Whitney U test was used for all two-group, and the Kruskal-Wallis's test was used for multiple-group comparisons. Bootstrapped receiver operating characteristic (ROC) curves and areas under the curve (AUC) were generated for the statistically significant histogram parameters to differentiate genotypic and phenotypic parameters.

RESULTS

Alveolar rhabdomyosarcomas had a statistically significant lower 10th Percentile (586.54 ± 164.52, mean ± std dev, values are in ×10-6mm2/s) than embryonal rhabdomyosarcomas (966.51 ± 481.33) with an AUC of 0.85 (95%CI. 0.73-0.95) for differentiating the two. The 10th percentile was also significantly different between FOXO1 fusion-positive (553.87 ± 187.64) and negative (898.07 ± 449.38) rhabdomyosarcomas with an AUC of 0.83 (95% CI 0.71-0.94). Alveolar rhabdomyosarcomas also had statistically significant lower Mean, Median, and Root Mean Squared ADC histogram values than embryonal rhabdomyosarcomas. Four, five, and seven of the 18 histogram parameters evaluated demonstrated a statistically significant increase with higher TNM stage, clinical group, assignment, and pretreatment risk stratification, respectively. For example, Entropy had an AUC of 0.8 (95% CI. 0.67-0.92) for differentiating TNM stage 1 from ≥ stage 2 and 0.9 (95% CI. 0.8-0.98) for differentiating low from intermediate or high-risk stratification.

CONCLUSION

Our findings demonstrate the potential of ADC histogram metrics to predict clinically relevant variables for rhabdomyosarcoma, including FOXO1 fusion status, histopathology, Clinical Group, TNM staging, and risk stratification.

Soft Tissue Sarcomas in Adolescents and Young Adults

Soft tissue sarcomas (STS) represent a heterogeneous group of extraskeletal mesenchymal tumors that affect individuals throughout the entire age continuum. Despite this pervasive influence, key differences exist in the presentation of these sarcomas across varying age groups that have prevented a more uniform approach to management. Notably, rhabdomyosarcoma (RMS) is more common in children, while most nonrhabdomyosarcoma soft tissue sarcoma (NRSTS) subtypes are more prevalent in adults. Older patients with NRSTS appear to have more molecularly complex biology and often present with more advanced disease compared with children. Poorer outcome disparities are observed in older patients with RMS despite receiving similar treatment as younger patients. In this review, we highlight differences in epidemiology, biology, and management paradigms for pediatric and adult patients with STS and explore opportunities for a unified approach to enhance the care and outcomes within the AYA population.

Contemporary preclinical mouse models for pediatric rhabdomyosarcoma: from bedside to bench to bedside

Background

Rhabdomyosarcoma (RMS) is the most common pediatric soft-tissue malignancy, characterized by high clinicalopathological and molecular heterogeneity. Preclinical in vivo models are essential for advancing our understanding of RMS oncobiology and developing novel treatment strategies. However, the diversity of scholarly data on preclinical RMS studies may challenge scientists and clinicians. Hence, we performed a systematic literature survey of contemporary RMS mouse models to characterize their phenotypes and assess their translational relevance.

Methods

We identified papers published between 01/07/2018 and 01/07/2023 by searching PubMed and Web of Science databases.

Results

Out of 713 records screened, 118 studies (26.9%) were included in the qualitative synthesis. Cell line-derived xenografts (CDX) were the most commonly utilized (n = 75, 63.6%), followed by patient-derived xenografts (PDX) and syngeneic models, each accounting for 11.9% (n = 14), and genetically engineered mouse models (GEMM) (n = 7, 5.9%). Combinations of different model categories were reported in 5.9% (n = 7) of studies. One study employed a virus-induced RMS model. Overall, 40.0% (n = 30) of the studies utilizing CDX models established alveolar RMS (aRMS), while 38.7% (n = 29) were embryonal phenotypes (eRMS). There were 20.0% (n = 15) of studies that involved a combination of both aRMS and eRMS subtypes. In one study (1.3%), the RMS phenotype was spindle cell/sclerosing. Subcutaneous xenografts (n = 66, 55.9%) were more frequently used compared to orthotopic models (n = 29, 24.6%). Notably, none of the employed cell lines were derived from primary untreated tumors. Only a minority of studies investigated disseminated RMS phenotypes (n = 16, 13.6%). The utilization areas of RMS models included testing drugs (n = 64, 54.2%), studying tumorigenesis (n = 56, 47.5%), tumor modeling (n = 19, 16.1%), imaging (n = 9, 7.6%), radiotherapy (n = 6, 5.1%), long-term effects related to radiotherapy (n = 3, 2.5%), and investigating biomarkers (n = 1, 0.8%). Notably, no preclinical studies focused on surgery.

Conclusions

This up-to-date review highlights the need for mouse models with dissemination phenotypes and cell lines from primary untreated tumors. Furthermore, efforts should be directed towards underexplored areas such as surgery, radiotherapy, and biomarkers.

Laryngeal Sarcomatoid Carcinoma With Rhabdomyoblastic Differentiation: A Potential Pitfall for Misdiagnosis As Rhabdomyosarcoma

Sarcomatoid carcinoma (SC) of the larynx is an uncommon subtype of squamous cell carcinoma which shows both squamous carcinoma and a sarcomatous component, including heterologous elements. The presence of rhabdomyosarcomatous elements in the larynx is extremely rare. Diagnosis of SC can be particularly challenging when the malignant epithelial component is not evident. We present a case of SC in a 72-year-old man with a superficial exophytic mass in the vocal cord initially misdiagnosed as rhabdomyosarcoma due to a predominant spindle cell component with rhabdomyoblastic features by morphology and immunohistochemistry. This case report aims to increase awareness that a rhabdomyoblastic heterologous component can be present in SC of the larynx and to consider this diagnosis in a mucosal exophytic malignant spindle cell neoplasm, even in the absence of epithelial differentiation.

Spindle Cell/Sclerosing Rhabdomyosarcoma of the Orbit

A 3-year-old boy developed proptosis over 3 weeks. CT and MRI disclosed a 3.2 × 1.9 cm soft-tissue mass of the right extraconal and intraconal orbit with sphenoid bone erosion. After debulking through an upper eyelid crease incision, the tumor was diagnosed as a spindle cell/sclerosing rhabdomyosarcoma. DNA sequencing was negative for an L122R mutation in MyoD1 . Spindle cell/sclerosing rhabdomyosarcoma is an uncommon variant of this neoplasm, and only 2 patients with orbital tumors have been reported in 2 case series. Spindle cell/sclerosing rhabdomyosarcomas confined to the orbit are considered to have an excellent prognosis when treated with chemotherapy and radiation therapy. Diagnosis and treatment planning rely on histology, immunohistochemistry, and molecular analysis.

A Novel Tongue-Based Tumor With an RREB1-MRTFB Fusion: Variant Rhabdomyosarcoma or Aggressive Variant of Ectomesenchymal Chondromyxoid Tumor

The presence of a FOXO1 fusion in a tumor is one of the most important prognostic factors in rhabdomyosarcoma. Most histologically defined alveolar rhabdomyosarcomas bear a FOXO1 fusion. We discuss a case that was initially thought to be a rhabdomyosarcoma but was later discovered to have an RREB1-MRTFB fusion. This fusion has never been reported in rhabdomyosarcoma but typically characterizes ectomesenchymal chondromyxoid tumor (ECT), a neoplasm with typically rather benign behavior. In this article, the authors discussed whether this patient's aggressive presentation represents a variation of ECT or an unusual case of rhabdomyosarcoma.

Rhabdomyosarcoma With FUS::TFCP2 Fusion in the Scalp: A Rare Case Report Depicting Round and Spindle cell Morphology

Rhabdomyosarcoma (RMS) is a nonepithelial malignant tumor that differentiates into immature skeletal muscle. It is currently classified into 4 main subtypes according to the WHO classification. However, based on clinicopathological and molecular findings, there has been an increasing number of cases that do not fit into any of these subtypes. TFCP2-rearranged RMS is a rare tumor with characteristic clinicopathological findings including a preference for the craniofacial bones, a spindle and epithelioid histomorphology, and positive immunohistochemistry for epithelial markers, ALK, and myogenic markers. In this report, we describe a rare case of RMS with FUS::TFCP2 fusion in the scalp of a 58-year-old man. Histologically, the tumor showed a biphasic pattern, with solid proliferation of round cells in the superficial areas and of spindle cells in the deep areas. Immunohistochemically, tumor cells were positive for pan keratin, myogenic markers (desmin, MYOD1, and myogenin), and ALK. Additionally, fluorescence in situ hybridization using a break-apart FUS probe revealed FUS rearrangement. RMS with FUS::TFCP2 fusion was suspected, and the fusion gene was finally confirmed by target fusion sequencing. We believe that detailed histological, immunohistochemical, and genetic findings were important for the diagnosis. The unique traits of this tumor were the biphasic histological appearance consisting of round and spindle cells and development in the skin and soft tissue.

Epithelioid Vascular Lesions: The Differential Diagnosis and Approach in Cytology and Small Biopsies

Vascular neoplasms are rare tumors with a multitude of clinical presentations and behavior, which make accurate identification and subclassification challenging on limited small biopsies. Within the spectrum of these lesions, the ones with epithelioid morphology, such as epithelioid hemangioendothelioma and epithelioid angiosarcoma, are particularly challenging given the morphologic overlap with nonvascular lesions and the limited cells due to hemodilution on sampling. Herein, we review the differential diagnosis of epithelioid vascular neoplasms, with a focus on the cytomorphology, differential diagnoses, and ancillary studies that pathologists should be aware of when evaluating small biopsies and aspirates, including novel translocations, and associated monoclonal immunohistochemistry antibodies, that can help in the diagnosis of some of these tumors. Awareness of these morphologic and ancillary study findings in these rare tumors will hopefully allow pathologists to recognize and render-specific diagnoses on limited samples of these challenging lesions.