Keywords
1. Alveolar Rhabdomyosarcoma
2. Ascites Diagnosis
3. Cytopathology
4. Myogenin Biomarkers
5. Mesothelial Cells Differentiation
Alveolar rhabdomyosarcoma (ARMS) is a malignant neoplasm recognized for its skeletal muscle lineage differentiation, predominantly encountered in younger populations. Its prevalence in older adults is rare, contributing to the diagnostic intricacies inherent in such cases. In a study published in the “Journal of Nippon Medical School = Nippon Ika Daigaku zasshi” (2020), a case report details the exceptional diagnosis of ARMS within the ascitic fluid of a 50-year-old woman, highlighting both the unpredictable nature of the disease and the convoluted path to its identification due to the cytological resemblances between ARMS cells and reactive mesothelial cells (DOI: 10.1272/jnms.JNMS.2018_86-404).
The report authored by Norio Motoda, Yuji Nakamura, Mutsumi Kuroki, Koichi Yoneyama, Saiko Isshiki, Ryuji Ohashi, and Zenya Naito, explores the anatomical and cytological complexities confronted during diagnosis, alongside a thorough literature review that situates the case within the broader scope of ARMS research.
Clinical Presentation and Initial Findings
The 50-year-old female patient, who originally presented with abdominal distension and discomfort, was subsequently found to possess an intra-abdominal mass associated with ample ascites. Imaging studies, including computed tomography, contributed little to the differential diagnosis, which hinged critically upon the cytological examination of the ascitic fluid.
Cytological Examination
The initial aspiration cytology yielded numerous round cells exhibiting subtle nuclear atypia and prominent nucleoli. Despite the discrete identification of rhabdomyoblastic cells, infrequent as they were, the phenotypic mimicry of the malignant cells to reactive mesothelial cells introduced significant diagnostic hurdles. Features such as cell cannibalism and “window” formation—more commonly found in reactive processes—clouded the clarity needed for a definitive diagnosis.
Diagnostic Challenges
The overlapping cytological characteristics between ARMS cells and reactive mesothelial cells stand as a formidable challenge in the diagnosis. Moreover, the age and gender of the patient added layers of complexity, as ARMS is typically seen in younger cohorts. To add, the presentation of abundant ascites is not regularly associated with ARMS, nudging clinicians and pathologists toward more common diagnoses such as peritoneal carcinomatosis, especially given the patient’s age.
Immunohistochemical Confirmation
Advancing towards a conclusive diagnosis necessitated histological biopsy of the intra-abdominal mass, followed by targeted immunohistochemical staining. The expression of myogenic markers, such as myogenin—integral to the differentiation and development of skeletal muscle cells—paved the way in confirming the attribution of the ascitic cells to ARMS. This myogenic determination crystallized the diagnosis, diverging from the initially hypothesized epithelial origin.
Impact of Myogenin as a Biomarker
The expression of myogenin in rhabdomyosarcoma, especially when considering its alveolar subtype, is deeply telling of the tumor cell lineage. Its role as a biomarker in pathologic studies is indicative not only of muscle differentiation but also serves as a pivotal cog in the diagnostic wheel, enabling differentiation from other neoplastic entities.
Literature Review
Investigating previous studies, the authors present a review of the available literature on ARMS cytology, its presentation within body fluids, and the diagnostic distinctions from other formative cellular malignancies. This case, along with others documented in the literature, demonstrates the importance of a broadened perspective when considering ARMS as a differential diagnosis in ascites, irrespective of patient demographic and typical clinical presentations.
Conclusion and Future Considerations
In sum, this reported case emphasizes the necessity for clinical vigilance and comprehensive cytologic-histologic correlation for diagnosing ARMS in ascites, especially in unanticipated patient populations. The ascitic fluid, often bypassed as a diagnostic tool for non-epithelial tumors, proved to be decisive in this case.
Finally, the report underscores the imperative need for further research and documentation of such anomalies, to construct a more robust diagnostic framework for clinicians faced with similarly enigmatic presentations.
References
1. Motoda, N., Nakamura, Y., Kuroki, M., Yoneyama, K., Isshiki, S., Ohashi, R., & Naito, Z. (2019). Exfoliation of Alveolar Rhabdomyosarcoma Cells in the Ascites of a 50-Year-Old Woman: Diagnostic Challenges and Literature Review. Journal of Nippon Medical School = Nippon Ika Daigaku zasshi, 86(4), 236-241. DOI: 10.1272/jnms.JNMS.2018_86-404
2. Goldstein, M., & Meller, I. (2001). Ascitic fluid cytology of diseases other than ovarian adenocarcinoma. Diagnostic Cytopathology, 25(2), 80-86.
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4. Rudzinski, E. R., Teot, L. A., & Anderson, J. R. (2011). The World Health Organization Classification of Skeletal Muscle Tumors in Pediatric Rhabdomyosarcoma: A report from the Children’s Oncology Group. Archives of Pathology & Laboratory Medicine, 135(10), 1288-1291.
5. Parham, D. M., & Ellison, D. A. (2006). Rhabdomyosarcomas in adults and children: an update. Archives of Pathology & Laboratory Medicine, 130(10), 1454-1465.