title: The clinical importance of parathyroid atypia: is long-term surveillance necessary?
abstract: BACKGROUND
  The uncommon diagnosis of atypical parathyroid adenoma (APA) creates a clinical conundrum for surveillance. We evaluated a large series of APA to determine long-term outcomes.
  
  
  METHODS
  Prospectively collected data were retrieved for patients with a diagnosis of histologic APA defined by presence of ≥2 criteria: clinical/intraoperative adherence, fibrotic bands, trabecular growth, or mitotic rate of >1/10 per high-power field without indisputable signs of malignancy. Follow-up was at 2 weeks, 6 months, and yearly thereafter.
  
  
  RESULTS
  From 1970 to 2014, 51 patients (1.2%) with primary hyperparathyroidism had a diagnosed APA. Mean age was 56 years (range, 19-83), and 61% were women. Intraoperatively, 11 of 51 glands (22%) were adherent, requiring concurrent thyroid lobectomy. Common microscopic findings were fibrosis (78%), trabecular growth (37%), and increased mitotic count (24%); the mean APA weight was 3.14 g (range, 167 mg-38 g). Loss of heterozygosity occurred in 25 of 38 tested patients (66%) at the p21 locus in 9 cases, at CDC73 and PTEN in 6, and at RB1 in 4 cases, with mean fractional allelic loss of 24% (range, 6-79). With mean follow-up of 5 years (range, 0.5-18), no patient has developed recurrence.
  
  
  CONCLUSIONS
  Over a mean follow-up of 5 years, we observed no recurrences after APA resection. Molecular features had no discernable impact, indicating that long-term follow-up may be unnecessary.
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA. Electronic address: mccoykl@upmc.edu.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: McCoy
authors.affiliation: Department of Pathology, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Raja R
authors.initials: RR
authors.lastname: Seethala
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Michaele J
authors.initials: MJ
authors.lastname: Armstrong
authors.affiliation: Department of Pathology, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Marina N
authors.initials: MN
authors.lastname: Nikiforova
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Stang
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Sally E
authors.initials: SE
authors.lastname: Carty
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Linwah
authors.initials: L
authors.lastname: Yip
mesh_terms: D000236:Adenoma / Q000150:complications / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000209:etiology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D010282:Parathyroid Neoplasms / Q000150:complications / Q000473:pathology* / Q000601:surgery; D016105:Parathyroidectomy; D012189:Retrospective Studies; D016896:Treatment Outcome