title: Calcifying epithelial odontogenic (Pindborg) tumor with malignant transformation and metastatic spread.
abstract: BACKGROUND
  Pindborg tumors (calcifying epithelial odontogenic tumors) are uncommon neoplasms of odontogenic origin most often located in the posterior mandible. First described in detail in 1955 by Pindborg, these tumors are considered benign but can be locally aggressive in nature, with recurrence rates of 10% to 15% reported. The malignant form of this tumor is exceedingly rare.
  
  
  METHODS
  We describe the case of a 64-year-old woman initially treated for a painful infected left mandibular third molar. The patient underwent extraction of the tooth and excision of an associated soft tissue component. Subsequent histologic review identified a Pindborg tumor of the left posterior mandible.
  
  
  RESULTS
  After initial excision, this tumor recurred twice, with the recurrences exhibiting a progression to a malignant Pindborg tumor (odontogenic carcinoma) with vascular invasion and spread to a cervical lymph node. Further treatment involved radical surgery and adjuvant radiotherapy. At last review 12 months after treatment, the patient was disease free.
  
  
  CONCLUSIONS
  This article describes only the second case of odontogenic carcinoma. The transformation from benign to malignant histologic findings has not previously been documented in this tumor. The salient clinical features of this case are presented along with supportive pathologic and radiologic evidence.
authors.affiliation: Department of Radiation Oncology, Westmead Hospital, Westmead, New South Wales, 2145, Sydney, Australia. michael@radonc.wsahs.nsw.gov.au
authors.forename: M J
authors.initials: MJ
authors.lastname: Veness
authors.forename: G
authors.initials: G
authors.lastname: Morgan
authors.forename: A P
authors.initials: AP
authors.lastname: Collins
authors.forename: D M
authors.initials: DM
authors.lastname: Walker
mesh_terms: D002471:Cell Transformation, Neoplastic; D005260:Female; D006801:Humans; D008339:Mandibular Neoplasms / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009808:Odontogenic Tumors / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D018714:Radiotherapy, Adjuvant