title: Concurrent occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma in the same thyroid should be considered as coincidental.
abstract: OBJECTIVE
  The simultaneous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) in the same thyroid gland is documented. In this study, we evaluated the prevalence and characteristics of patients with concurrent MTC and PTC. Design Retrospective analysis of patients with MTC in a single centre and review of the literature.
  
  
  METHODS
  Patients with MTC who underwent initial surgical treatment between 1996 and 2006 at Asan Medical Centre, Seoul, Korea were enrolled. We additionally reviewed the medical records of patients who initially underwent surgery for Graves' disease (GD) or follicular thyroid carcinoma (FTC) during the same period. The concurrent occurrence rate of PTC in MTC patients was compared with that in GD and FTC patients.
  
  
  RESULTS
  Ten of 53 (19%) MTC patients displayed the concomitant PTC. In all 10 cases, the MTC and PTC components were separated by normal thyroid tissue, with the maximal diameters of PTC being less than 1.0 cm in the majority of patients. The rates of concurrent PTC in patients with MTC, GD and FTC were 19%, 15% and 19%, respectively, which were not significantly different.
  
  
  CONCLUSIONS
  Our results suggest that the occurrence of concurrent MTC/PTC is generally a simple reflection of incidental papillary microcarcinoma.
authors.affiliation: Department of Endocrinology and Metabolism, Asan Medical Centre, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea.
authors.forename: Won Gu
authors.initials: WG
authors.lastname: Kim
authors.forename: Gyungyub
authors.initials: G
authors.lastname: Gong
authors.forename: Eui Young
authors.initials: EY
authors.lastname: Kim
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.forename: Suck Joon
authors.initials: SJ
authors.lastname: Hong
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
mesh_terms: D000328:Adult; D018276:Carcinoma, Medullary / Q000175:diagnosis* / Q000453:epidemiology; D002291:Carcinoma, Papillary / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D055815:Young Adult