Epithelioid Rhabdomyosarcoma; a case report with immunohistochemical and molecular study

Rhabdomyosarcoma: Updates on classification and the necessity of molecular testing beyond immunohistochemistry

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents under the age of 20. The current World Health Organization (WHO) classification for soft tissue and bone tumors recognizes 4 distinct subtypes of RMS based on clinicopathological and molecular genetic features: embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. However, with the increased use of molecular techniques, the classification of rhabdomyosarcoma has been evolving rapidly. New subtypes such as osseus RMS harboring TFCP2/NCOA2 fusions or RMS arising in inflammatory rhabdomyoblastic tumor have been emerging within the last decade, adding to the complexity of diagnosing skeletal muscle tumors. This review article provides an overview of classically recognized distinctive subtypes as well as new, evolving subtypes and discusses important morphologic, immunophenotypic and molecular genetic features of each subtype including recommendations for a diagnostic approach of malignant skeletal muscle neoplasms.

Rhabdomyosarcoma With Epithelioid Features And NSD3::FOXO1 Fusion: Evidence For Reconsideration Of Previously Reported FOXO1::FGFR1 Fusion

Epithelioid rhabdomyosarcoma is a rare rhabdomyosarcoma variant for which no diagnostic recurrent driver genetic events have been identified. Here we report a rapidly progressive and widely metastatic rhabdomyosarcoma with epithelioid features that arose in the thigh of a male infant. Conventional cytogenetics revealed a t(8;13)(p11.2;q14) translocation. Fluorescence in situ hybridization studies showed rearrangement of FOXO1 and amplification of its 3" end, and rearrangement of NSD3 and amplification of its 5` end. Next generation sequencing identified a NSD3::FOXO1 fusion, which is a previously unreported gene fusion. We also review the historic report of a FOXO1::FGFR1 fusion in a solid variant of alveolar rhabdomyosarcoma and propose that NSD3::FOXO1 fusion may have been the more appropriate interpretation of the data presented in that report.

Epithelioid and spindle rhabdomyosarcoma with TFCP2 rearrangement in abdominal wall: a distinctive entity with poor prognosis

BACKGROUND

Epithelioid and spindle rhabdomyosarcoma (ES-RMS) with TFCP2 rearrangement is a recently discovered rare variant of rhabdomyosarcoma composed of epithelioid and spindle cells, because it shows extraordinarily adverse prognosis and is easily misdiagnosed as other epithelioid or spindle cell tumors.

METHODS

A rare case of ES-RMS with TFCP2 rearrangement was presented and English literatures in Pubmed online up to 01 July 2022 were gathered by two authors for a systematic review according to the inclusion and exclusion criteria.

CASE PRESENTATION/RESULTS

We report a case of ES-RMS in an early 30s-years-old female, the neoplastic cells are remarkably immunoreactive with CK(AE1/AE3), and partially with ALK protein. Unexpectedly, the tumor shows TFCP2 rearrangement with coexistence of increased copy numbers of EWSR1 and ROS1 gene and MET gene mutation. Besides, Next-generation sequencing for genetic mutational profiling revealed frequent MET exon14 mutations in chromosome 7, most of which are C > T nonsynonymous SNV, and exon42 of ROS1 in chromosome 6 showed frequent G > T mutation up to 57.54%. In addition, neither MyoD1 mutation nor gene fusions were detected. Moreover, the patient shows high tumor mutational burden (TMB) up to 14.11 counts/Mb. Finally, as many cases of ES-RMS including our case had local progression or metastasis, we find, similar to epithelioid rhabdomyosarcoma (median survival time is 10 month), ES-RMS shows a more aggressive behavior and adverse prognosis (median survival time is 17 month) than spindle cell/sclerosing rhabdomyosarcoma (median survival time is 65 month) according previous studies.

CONCLUSIONS

ES-RMS with TFCP2 rearrangement is a rare malignant tumor and easily confused with other epithelioid or spindle cell tumors, it may harbor additional gene alteration in addition to TFCP2 rearrangement, such as MET mutation, increased copy numbers of EWSR1 and ROS1 gene, high TMB. Most importantly, it may show very poor outcome with extensive metastasis.

Fisher discriminant model based on LASSO logistic regression for computed tomography imaging diagnosis of pelvic rhabdomyosarcoma in children

Computed tomography (CT) has been widely used for the diagnosis of pelvic rhabdomyosarcoma (RMS) in children. However, it is difficult to differentiate pelvic RMS from other pelvic malignancies. This study aimed to analyze and select CT features by using least absolute shrinkage and selection operator (LASSO) logistic regression and established a Fisher discriminant analysis (FDA) model for the quantitative diagnosis of pediatric pelvic RMS. A total of 121 pediatric patients who were diagnosed with pelvic neoplasms were included in this study. The patients were assigned to an RMS group (n = 36) and a non-RMS group (n = 85) according to the pathological results. LASSO logistic regression was used to select characteristic features, and an FDA model was constructed for quantitative diagnosis. Leave-one-out cross-validation and receiver operating characteristic (ROC) curve analysis were used to evaluate the diagnostic ability of the FDA model. Six characteristic variables were selected by LASSO logistic regression, all of which were CT morphological features. Using these CT features, the following diagnostic models were established: (RMS group)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${G}_{1}=-14.283+6.613{x}_{1}+5.333{x}_{2}+5.753{x}_{3}+12.361{x}_{4}+8.095{x}_{5}-0.715{x}_{6}$$\end{document}G1=-14.283+6.613x1+5.333x2+5.753x3+12.361x4+8.095x5-0.715x6; (Non-RMS group)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${G}_{2}=-2.008+3.539{x}_{1}+1.080{x}_{2}+1.154{x}_{3}+2.307{x}_{4}+1.656{x}_{5}+1.380{x}_{6}$$\end{document}G2=-2.008+3.539x1+1.080x2+1.154x3+2.307x4+1.656x5+1.380x6, where \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${x}_{1}$$\end{document}x1, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${x}_{2}$$\end{document}x2, … and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${x}_{6}$$\end{document}x6 are lower than normal muscle density (1 = yes; 0 = no), multinodular fusion (1 = yes; 0 = no), enhancement at surrounding blood vessels (1 = yes; 0 = no), heterogeneous progressive centripetal enhancement (1 = yes; 0 = no), ring enhancement (1 = yes; 0 = no), and hemorrhage (1 = yes; 0 = no), respectively. The calculated area under the ROC curve (AUC) of the model was 0.992 (0.982–1.000), with a sensitivity of 94.4%, a specificity of 96.5%, and an accuracy of 95.9%. The calculated sensitivity, specificity and accuracy values were consistent with those from cross-validation. An FDA model based on the CT morphological features of pelvic RMS was established and could provide an easy and efficient method for the diagnosis and differential diagnosis of pelvic RMS in children.

Primary Epithelioid Rhabdomyosarcoma of the Liver: Case Report of an Unusual Histological Variant

Rhabdomyosarcoma (RMS) is a soft tissue tumor with striated muscle cell differentiation. It mostly occurs in children. While it can affect any part of the body, it commonly involves the urogenital organs, head and neck including the parameninges and orbit, and limbs. We describe an adult case of primary epithelioid RMS of the liver. A 71-year-old man presented with a 5.6 cm liver mass. Tumor histology revealed diffuse proliferation of small epithelioid cells and focal spindle cells. The tumor cells were immunohistochemically positive for myogenin (positive ratio 30%), desmin, Myo D1, and CD56. The tumor weakly expressed MDM2 and did not express CDK4. This suggested that dedifferentiated liposarcoma with a rhabdomyosarcomatous component was unlikely. There was no fusion gene of PAX3-FKHR or PAX7- FKHR to indicate alveolar RMS by RT-PCR. Subsequently, RNA Pan-Cancer Targeted sequencing was performed for 1385 genes revealed a single base substitution (c.742C>T) in TP53 that changes an amino acid (p.Arg248Trp). No fusion gene was found. No other primary RMS lesions were detected aside from the liver lesion. The tumor was diagnosed as a primary epithelioid RMS of the liver. His RMS already metastasized to the lymph nodes of the entire body. The patient declined further therapy and died one year later. This was the first case report of a primary epithelioid RMS of the liver.

Computed tomography (CT) features of pelvic rhabdomyosarcoma (RMS) in children

BACKGROUND

Currently, there are few literature reports on the CT features of pelvic rhabdomyosarcoma, most of which exist in the form of case reports, and some literature reports have suggested that CT features of pelvic rhabdomyosarcoma lack specificity. This study was designed to investigate the CT features of pelvic RMS in children to provide imaging evidence for clinical diagnosis.

METHODS

We retrospectively reviewed radiographic and clinical data of all paediatric patients with pelvic neoplastic lesions pathologically proven to be malignant in our hospitals from January 2012 through March 2021. The data of the included paediatric patients were divided into two groups according to whether the pathology results indicated RMS. CT features of RMS (n= 37) and non-RMS (n= 91) were compared by two abdominal radiologists.

RESULTS

A total of 9 CT features were statistically significant for the diagnosis of pelvic RMS in children (p＜0.05). The sensitivity (range, 0.64-0.74) and specificity (range, 0.86-0.93) of the CT features showing multinodular fusion, surrounding blood vessels, and heterogeneous progressive centripetal enhancement were both relatively high. The CT features indicating lower than muscle density, necrosis, non-calcification and non-haemorrhage exhibited high specificity (range, 0.86-0.97), but the sensitivity (range, 0.32-0.40) was relatively low, while the sensitivity (range, 0.37-0.46) and specificity (range, 0.75-0.83) of other CT features used for diagnosing pelvic RMS, namely, lobulated and lymphatic metastasis, were both relatively low.

CONCLUSION

Pelvic rhabdomyosarcoma in children has its own specific CT features.

Rhabdomyosarcoma with epithelioid morphology: A challenging cytologic diagnosis in a pleural effusion

Rhabdomyosarcomas (RMS) are rare malignant skeletal muscle tumors that present more commonly in pediatric populations. The WHO currently classifies RMS into four types, embryonal, alveolar, pleomorphic, and spindle cell/sclerosing variants. Epithelioid rhabdomyosarcoma (EpiRMS) is another rare, recently described subtype of RMS presenting in older patients with a male predominance and has a rapidly progressive clinical course with frequent metastases. EpiRMS closely mimics poorly differentiated carcinoma or melanoma, demonstrating discohesive large epithelioid cells with abundant eosinophilic cytoplasm, frequent glassy cytoplasmic inclusions, large vesicular nuclei, and prominent nucleoli. We present a case of metastatic rhabdomyosarcoma with features reminiscent of EpiRMS presenting as a pleural effusion, closely followed by an inguinal lymph node biopsy. The malignant cells in the pleural fluid were diffusely positive for desmin, negative for MyoD1, myogenin, S100 and SOX10, and retained INI-1 expression. Subsequent lymph node biopsy demonstrated identical malignant epithelioid cells that were positive for desmin, myoD1 and myogenin, and a cytological diagnosis of "metastatic rhabdomyosarcoma, favor epithelioid rhabdomyosarcoma" was given considering the concurrent lymph node biopsy morphology and immunoprofile. A diagnosis of rhabdomyosarcoma, though rare and challenging, should not be overlooked when considering malignant cells with an epithelioid morphology in cytology specimens.

Epithelioid Rhabdomyosarcoma: Report of a Cutaneous Case and Literature Review of a Recently Described Variant of Rhabdomyosarcoma

Rhabdomyosarcoma affects mainly pediatric patients and is currently classified into 4 categories: embryonal, alveolar, pleomorphic, and spindle cell/sclerosing. Epithelioid rhabdomyosarcoma is a recently described variant of rhabdomyosarcoma in which primary cutaneous presentation is infrequent. In this brief report, we describe a rare case of epithelioid rhabdomyosarcoma in an 81-year-old man, presenting as a skin lesion in the neck, which increased in size in 1 month. After imaging evaluation, a solid cervical mass was discovered. A biopsy was performed, and the diagnosis of epithelioid rhabdomyosarcoma was rendered. The patient died due to rapid progression of the tumor. To make an accurate diagnosis and ensure appropriate patient management, it is necessary to be aware of this variant and use proper immunohistochemical stains when facing an epithelioid malignancy, expanding the differential diagnosis of epithelioid neoplasms.

Epithelioid rhabdomyosarcoma: Report of the first case in the jaw

OBJECTIVES

Epithelioid rhabdomyosarcoma (EpiRMS) is a novel morphologically distinct variant of rhabdomyosarcoma, with an unusually challenging microscopic diagnosis. The occurrence of rhabdomyosarcomas in the jaws is extremely rare. This study presents the first case of EpiRMS in the jaw (mandible) and a literature review of the previous 35 cases of EpiRMS.

STUDY DESIGN

Here, we report a case of EpiRMS affecting an 18-year-old male patient. Clinical, imaging, microscopic, and immunohistochemical features are discussed and previously reported cases of EpiRMS are reviewed.

RESULTS

An 18-year-old male patient presented with an exophytic sessile growth on the buccal gingiva, and orthopantomography revealed irregular bone loss. Microscopic analysis showed a large number of cells with epithelioid appearance. Immunohistochemistry staining was positive for desmin, myogenin, MyoD1, smooth muscle actin, h-caldesmon, INI-1, and AE1-AE3. The patient's disease was staged as T4aN1M0 and was treated with surgical excision combined with chemotherapy.

CONCLUSIONS

The occurrence of RMS in the mandible is rare, and this is the first case of EpiRMS in the jaw. EpiRMS is an unusual histologic subtype that mimics other sarcomas and epithelial malignancies, making diagnosis a challenge. A specific immunohistochemistry panel aids in the diagnosis. EpiRMS has an aggressive course and an unfavorable prognosis.