title: Prostatic and urothelial metastasis in the same lymph node: a case report.
abstract: BACKGROUND
  Collision metastasis is a rare phenomenon in which metastases of carcinoma from 2 separate primary tumors occur in the same lymph node. We summarize here the clinical course and highlight the histological challenges in the diagnosis of this rare phenomenon.
  
  
  METHODS
  A biopsy performed due to gross hematuria by endoscopic resection revealed an infiltrative high-grade urothelial carcinoma in a 75-year-old man receiving androgen deprivation therapy due to biopsy-proven high-grade prostate cancer. A radical cystectomy, with regional lymphadenectomy and prostatectomy, was performed. Three nodes appeared to have metastatic foci from both primary tumors: prostatic and urothelial cancer. The presence of the 2 tumor types colliding in the same lymph nodes was confirmed by immunohistochemical stains.
  
  
  CONCLUSIONS
  In a patient with simultaneous tumors it is important to remember that a part of lymph node metastases with histological polymorphic appearance may result from a collision metastasis. In light of the important therapeutic consequences, a differential diagnosis is needed, suggesting appropriate immunohistochemical investigations.
authors.forename: Elena
authors.initials: E
authors.lastname: Pacella
authors.forename: Francesco
authors.initials: F
authors.lastname: Ricci
authors.forename: Maurizio
authors.initials: M
authors.lastname: Colecchia
authors.forename: Francesco
authors.initials: F
authors.lastname: Boccardo
authors.forename: Antonio
authors.initials: A
authors.lastname: Lopez-Beltran
authors.forename: Bruno
authors.initials: B
authors.lastname: Spina
mesh_terms: D000230:Adenocarcinoma / Q000556:secondary*; D000368:Aged; D002295:Carcinoma, Transitional Cell / Q000556:secondary*; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D016609:Neoplasms, Second Primary / Q000556:secondary*; D011471:Prostatic Neoplasms / Q000473:pathology*; D001749:Urinary Bladder Neoplasms / Q000473:pathology*