title: Urachal adenocarcinoma that metastasized to breast was misinterpreted as primary breast mucinous carcinoma: A rare case report and literature review.
abstract: BACKGROUND
  The urachus is a vestigial tubular structure that connects the urinary bladder to the allantois during early embryonic development. Urachal carcinoma develops in the urachus, which is an embryological remnant of the urogenital sinus and allantois. The estimated annual incidence of urachal carcinoma in the general population is 0.01% of all cancers in adults. Moreover, urachal carcinoma accounts for 0.34% to 0.7% of all bladder carcinoma cases. And breast metastasis is extremely rarer.
  
  
  RESULTS
  A 42-year-old woman was admitted to our hospital with a palpable mass in the outer upper quadrant of the right breast, which was misinterpreted as a carcinoma that originated from the breast. Subsequently, she underwent surgery without any further meticulous examination. Immunohistochemistry analysis revealed positivity for CK20, Villin, and CDX-2 and negativity for CK7. After further inspection, a mass was found in the bladder dome using 18F-fluorodeoxyglucose positron emission tomography and computed tomography. The mass was surgically removed.
  
  
  CONCLUSIONS
  Pathologic and immunohistochemical examination confirmed that the mass was urachal mucinous adenocarcinoma and mucinous adenocarcinoma to the right breast. The patient has been followed up without recurrence for 8 months.
authors: School of Medical and Life Sciences, Shandong Academy of Medical Sciences, Jinan University, Jinan, China Department of Radiation Oncology Ward 2, Shandong Cancer Hospital Affiliated to Shandong University Department of Radiation Oncology, Affiliated hospital of Shandong Academy of Medical Sciences Department of Pathology, Shandong Cancer Hospital Affiliated to Shandong University.
authors: Xiang-Rong
authors: XR
authors: Zhao
authors: Chao
authors: C
authors: Gao
authors: Yong
authors: Y
authors: Zhang
authors: Xiao-Dong
authors: XD
authors: Yan
authors: Lei
authors: L
authors: Kong
authors: Wei
authors: W
authors: Qu
authors: Jia
authors: J
authors: Li
authors: Yong-Sheng
authors: YS
authors: Gao
authors: Yong-Hua
authors: YH
authors: Yu
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000000981:diagnostic imaging / Q000556:secondary*; D002288:Adenocarcinoma, Mucinous / Q000175:diagnosis*; D000328:Adult; D001943:Breast Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology / Q000556:secondary*; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D000072078:Positron Emission Tomography Computed Tomography; D001749:Urinary Bladder Neoplasms / Q000737:chemistry / Q000000981:diagnostic imaging / Q000473:pathology* / Q000556:secondary