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JPTM > Ahead-of Print

doi: https://doi.org/10.4132/jptm.2018.12.07    [Epub ahead of print]
Encapsulated Papillary Thyroid Tumor with Delicate Nuclear Changes and a KRAS Mutation as a Possible Novel Subtype of Borderline Tumor
Kenji Ohba1,2, Norisato Mitsutake3, Michiko Matsuse3, Tatiana Rogounovitch3, Nobuhiko Nishino4, Yutaka Oki2, Yoshie Goto1, Kennichi Kakudo5
1Department of Internal Medicine, Enshu Hospital, Shizuoka, Japan
2Department of Family and Community Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
3Department of Radiation Medical Sciences, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan
4Department of Surgery, Maruyama Hospital, Shizuoka, Japan
5Department of Pathology, Nara Hospital, Kindai University Faculty of Medicine, Nara, Japan
Corresponding Author: Kennichi Kakudo ,Tel: +81-743-77-0880, Fax: +81-743-77-0890, Email: kakudo@thyroid.jp
Received: November 8, 2018;  Revised: December 5, 2018  Accepted: December 7, 2018.  Published online: January 14, 2019.
Although papillary thyroid carcinoma (PTC)-type nuclear changes are the most reliable morphological feature in the diagnosis of PTC, the nuclear assessment used to identify these changes is highly subjective. Here, we report a noninvasive encapsulated thyroid tumor with a papillary growth pattern measuring 23 mm at its largest diameter with a nuclear score of 2 in a 26-year-old man. After undergoing left lobectomy, the patient was diagnosed with an encapsulated PTC. However, a second opinion consultation suggested an alternative diagnosis of follicular adenoma with papillary hyperplasia. When providing a third opinion, we identified a low MIB-1 labeling index and a heterozygous point mutation in the KRAS gene but not the BRAF gene. We speculated that this case is an example of a novel borderline tumor with a papillary structure. Introduction of the new terminology “noninvasive encapsulated papillary RAS-like thyroid tumor” (NEPRAS) without the word “cancer” might relieve the psychological burden of patients in a way similar to the phrase “noninvasive follicular thyroid neoplasm with papillary-like nuclear features” (NIFTP).
Key Words: Borderline/precursor tumor; Observer variation; RAS-like tumor
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