title: Extensive rhabdomyosarcomatous differentiation in recurrent low-grade urothelial carcinoma of the bladder after transurethral resection: a case report.
abstract: BACKGROUND
  Sarcomatoid 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.
  
  
  METHODS
  A 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Urology, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. kameim@kochi2.hosp.go.jp.
authors.forename: Maiko
authors.initials: M
authors.lastname: Kamei
authors.affiliation: Department of Clinical Investigation, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. shinoharat@kochi2.hosp.go.jp.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Shinohara
authors.affiliation: Division of Urology, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. kasaharak@kochi2.hosp.go.jp.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Kasahara
authors.affiliation: Division of Urology, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. t-kuno@m2.gyao.ne.jp.
authors.forename: Takahira
authors.initials: T
authors.lastname: Kuno
authors.affiliation: Division of Pathology, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. narusek@kochi2.hosp.go.jp.
authors.forename: Keishi
authors.initials: K
authors.lastname: Naruse
authors.affiliation: Division of Urology, National Hospital Organization National Kochi Hospital, 1-2-25 Asakuranishimachi, Kochi, 780-8077, Japan. watanabeh@kochi2.hosp.go.jp.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D015653:Cystectomy; D003937:Diagnosis, Differential; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000601:surgery*; D012208:Rhabdomyosarcoma / Q000175:diagnosis* / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis* / Q000601:surgery*