title: A histological comparison of deep and superficial lobe pleomorphic adenomas of the parotid gland.
abstract: BACKGROUND
  Excision of parotid superficial lobe pleomorphic adenomas requires removal of a surrounding cuff of normal parotid tissue. Less aggressive dissection in removing pleomorphic adenomas that occur in the deep lobe of the parotid gland does not seem to compromise prognosis in these patients. We attempted to define histologic characteristics, differentiating superficial and deep lobe tumors, in an attempt to explain this clinical phenomenon.
  
  
  METHODS
  Thirty-one pleomorphic adenomas, 12 deep-lobe tumors, and 19 superficial lobe tumors were analyzed and compared, looking at tumor size, capsule thickness, penetration of tumor through capsule, and predominant cell types present.
  
  
  RESULTS
  The superficial lobe tumors had significantly thinner capsules (p =.02). There was increased extracapsular extension of tumor in the superficial lobe group compared with the deep lobe group (79% and 58%, respectively). The tumors were larger in patients with deep lobe lesions (2.6 cm vs 3.6 cm). There was no difference in predominant cell types.
  
  
  CONCLUSIONS
  The anatomic location of deep lobe tumors is a likely explanation for the histologic differences observed in this study. These important differences allow less aggressive dissection in deep lobe tumors without compromising prognosis.
authors.affiliation: Department of Otolaryngology, St. James' Hospital, James St., Dublin 8, Ireland. michaelsharney@eircom.net
authors.forename: Michael S
authors.initials: MS
authors.lastname: Harney
authors.forename: Colette
authors.initials: C
authors.lastname: Murphy
authors.forename: Stephen
authors.initials: S
authors.lastname: Hone
authors.forename: Mary
authors.initials: M
authors.lastname: Toner
authors.forename: Conrad V
authors.initials: CV
authors.lastname: Timon
mesh_terms: D008949:Adenoma, Pleomorphic / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000601:surgery; D010307:Parotid Neoplasms / Q000473:pathology* / Q000601:surgery