title: Revisiting Low-Risk Thyroid Papillary Microcarcinomas Resected Without Observation: Was Immediate Surgery Necessary?
abstract: BACKGROUND
  Low-risk thyroid papillary microcarcinomas (PMCs) without evidence of metastasis grow slowly if at all. However, we recommended surgery for tumors touching the trachea (TR) or located in the course of the recurrent laryngeal nerve (RN). Here we compared the cases of low-risk PMC patients who underwent immediate surgery to cases of TR- and RN-involved PMCs.
  
  
  METHODS
  We enrolled 1143 low-risk PMC patients who underwent immediate surgery in the years 2006-2014. The PMCs of 437 patients touched the TR on imaging studies: 270, 104, and 63 were graded as low, intermediate, and high risk, respectively, for TR invasion based on the angles between the tumor and the TR surface. The tumor was in the course of the RN in 144 patients, with 35 graded low risk and 109 high risk for RN invasion based on the normal rim of the thyroid in the direction of the RN.
  
  
  RESULTS
  Invasion of the TR cartilage was observed only in high-risk patients. Peritracheal connective tissue was resected in 21, 15, and 6 of the high-, intermediate- and low-risk patients, respectively. Significant invasion of the RN requiring complete resection was observed in only nine patients at high risk for RN invasion. The incidence of TR invasion in high- and intermediate patients and the incidence of RN invasion in the high-risk patients were significantly higher than those of the low-risk patients. Tumors <7 mm did not show TR or RN invasion.
  
  
  CONCLUSIONS
  Among PMCs that touched the TR or were located in the course of the RN, observation could be the first choice for tumors < 7 mm and those ≥ 7 mm judged as low risk for TR or RN invasion. However, for PMCs with high-risk features, immediate surgery after cytological diagnosis by a needle aspiration biopsy is recommended.
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan. ito01@kuma-h.or.jp.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan. miyauchi@kuma-h.or.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Miyauchi
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Oda
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Kihara
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe, 650-0011, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Miya
mesh_terms: D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000601:surgery*; D011379:Prognosis; D012086:Reoperation; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000601:surgery*; D013965:Thyroidectomy / Q000379:methods*; D014057:Tomography, X-Ray Computed