title: Parathyroid carcinoma encountered after minimally invasive focused parathyroidectomy may not require further radical surgery.
abstract: BACKGROUND
  Parathyroid carcinoma accounts for <1% of tumors in primary hyperparathyroidism (PHPT). Distinguishing parathyroid malignancy from benign disease is difficult both before and after initial surgery. Despite the improved specificity of a malignant diagnosis with immunohistochemistry for parafibromin and PGP9.5, proven metastatic behavior remains the gold standard of diagnosis. Minimally invasive focused parathyroidectomy (MIP) is widely performed in patients with PHPT and positive localization studies; thus, it is inevitable that some parathyroid carcinomas will be encountered at MIP. We present our experience of this rare entity.
  
  
  METHODS
  The present study represents a surgical case series of patients with parathyroid carcinoma encountered after MIP. The clinicopathological features of benign and malignant parathyroid tumors were compared. Multiple regression analysis was undertaken to compare indicators of malignancy.
  
  
  RESULTS
  Between May 1999 and April 2010, a total of 1,292 patients underwent MIP at the University of Sydney Endocrine Surgical Unit, and a histopathological diagnosis of parathyroid carcinoma was made in seven patients (0.5%). Staining for parafibromin and/or PGP9.5 was abnormal in five carcinomas (71%). Despite subsequent unilateral thyroid lobectomy and lymphadenectomy in six patients, no further malignancy was identified in any specimens. Compared to controls, preoperative calcium (p = 0.04) and parathyroid hormone (p = 0.01) were significantly higher in patients with malignancy. The positive predictive value of these parameters for carcinoma was 56 and 75%, respectively.
  
  
  CONCLUSIONS
  In patients diagnosed with parathyroid carcinoma after MIP where preoperative imaging had already demonstrated localized disease, revision en bloc surgery did not reveal any residual disease. The benefits of further radical surgery for parathyroid carcinoma after MIP remain controversial.
authors.affiliation: University of Sydney Endocrine Surgical Unit, 202/69 Christie St., St. Leonards, NSW, 2065, Australia.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: O'Neill
authors.forename: Conan
authors.initials: C
authors.lastname: Chan
authors.forename: James
authors.initials: J
authors.lastname: Symons
authors.forename: Diana L
authors.initials: DL
authors.lastname: Learoyd
authors.forename: Stan B
authors.initials: SB
authors.lastname: Sidhu
authors.forename: Leigh W
authors.initials: LW
authors.lastname: Delbridge
authors.forename: Anthony
authors.initials: A
authors.lastname: Gill
authors.forename: Mark S
authors.initials: MS
authors.lastname: Sywak
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000209:etiology / Q000601:surgery*; D016015:Logistic Models; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D010282:Parathyroid Neoplasms / Q000150:complications / Q000473:pathology / Q000601:surgery*; D016105:Parathyroidectomy / Q000379:methods*; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D016896:Treatment Outcome