Abstract
IntroductionSarcomatoid carcinoma of the urinary bladder is a rare bidirectional malignant neoplasm with epithelial and mesenchymal differentiation. The epithelial component is mainly high-grade urothelial carcinoma, and the mesenchymal component includes rhabdomyosarcoma. However, proper differential diagnosis of adult rhabdomyosarcomatous tumors of the bladder can be a challenge. Moreover, low-grade urothelial carcinoma as the epithelial component of sarcomatoid carcinoma has not been reported.Case presentationA 64-year-old Asian man with a history of transurethral resection of low-grade urothelial carcinoma of the bladder visited our department with complaints of frequent urination and macroscopic hematuria. Computed tomography and magnetic resonance imaging demonstrated a large mass located in the anterior wall of the bladder. Pathological diagnosis of transurethral biopsy was low-grade, non-invasive papillary urothelial carcinoma, and tumor tissue was removed by total cystectomy. Immunohistochemical studies and fluorescence in situ hybridization assay of the resected neoplastic tissue revealed extensive rhabdomyosarcomatous differentiation causing the formation of a large pedunculated polyp with a papillary appearance of recurrent low-grade urothelial carcinoma. No evidence of recurrence was detected during 2 years of follow-up without further treatment.ConclusionsUrothelial carcinoma of the urinary bladder with extensive rhabdomyosarcomatous differentiation is rare, but it should be considered in the differential diagnosis even when urothelial carcinoma coexisting with a rhabdomyosarcomatous component is low-grade and non-invasive.
Highlights
Sarcomatoid carcinoma of the urinary bladder is a rare bidirectional malignant neoplasm with epithelial and mesenchymal differentiation
Immunohistochemical studies and fluorescence in situ hybridization assay of the resected neoplastic tissue revealed extensive rhabdomyosarcomatous differentiation causing the formation of a large pedunculated polyp with a papillary appearance of recurrent low-grade urothelial carcinoma
Urothelial carcinoma of the urinary bladder with extensive rhabdomyosarcomatous differentiation is rare, but it should be considered in the differential diagnosis even when urothelial carcinoma coexisting with a rhabdomyosarcomatous component is low-grade and non-invasive
Summary
UC of the urinary bladder with extensive rhabdomyosarcomatous differentiation is rare, but it should be considered in the differential diagnosis even when UC coexisting with a rhabdomyosarcomatous component is of low grade, especially in cases of a tumor that is unexpectedly large for low-grade UC. More molecular biological research is needed to obtain insight into the pathogenic factors involved in rhabdomyosarcomatous differentiation in UC to improve the management of this disease. Consent Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent form is available for review by the Editor-in-Chief of this journal. Competing interests The authors declare that they have no competing interests. Authors’ contributions MK drafted the initial manuscript. TS edited and submitted the manuscript for publication. KK and TK were involved in diagnosing and treating the patient. HW was the attending physician throughout the patient’s disease course. All authors read and approved the final manuscript
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