title: Extremely Well-Differentiated Papillary Thyroid Carcinoma Resembling Adenomatous Hyperplasia Can Metastasize to the Skull: A Case Report.
abstract: We describe herein histologic, immunohistochemical, and molecular findings and clinical manifestations of a rare case of an extremely well differentiated papillary thyroid carcinoma (EWD-PTC). Similarly, it is also difficult to diagnose follicular variant papillary thyroid carcinoma (FVPTC), whose diagnosis is still met with controversy. A recently reported entity of well-differentiated tumor of uncertain malignant potential (WDT-UMP) is added to the diagnostic spectrum harboring EWD-PTC and FVPTC. We report this case, because EWD-PTC is different from FVPTC in its papillary architecture, and also from WDT-UMP in its recurrence and metastatic pattern. These morphologically deceptive entities harbored diagnostic difficulties in the past because the diagnosis depended solely on histology. However, they are now diagnosed with more certainty by virtue of immunohistochemical and molecular studies. We experienced a case of EWD-PTC, which had been diagnosed as adenomatous hyperplasia 20 years ago and manifested recurrence with lymph node (LN) metastasis 7 years later. After another 7 years of follow-up, a new thyroid lesion had developed, diagnosed as FVPTC, with LN metastasis of EWD-PTC. One year later, the patient developed metastatic FVPTC in the skull. Immunohistochemically, the EWD-PTC was focally positive for CK19, negative for galectin-3, and focally negative for CD56. Molecular studies revealed BRAF-positivity and K-RAS negativity. The FVPTC in the left thyroid showed both BRAF and K-RAS negativity. In conclusion, EWD-PTC and FVPTC share similar histologic features, but they are different tumors with different molecular biologic and clinical manifestations. A large cohort of EWD-PTC should be included in further study.
authors.affiliation: Department of Pathology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ju Yeon
authors.initials: JY
authors.lastname: Pyo
authors.affiliation: Department of Pathology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jisup
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Pathology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Sung Eun
authors.initials: SE
authors.lastname: Choi
authors.affiliation: Department of Pathology, CHA Gangnam Hospital, CHA University Medical School, Seoul, Korea.
authors.forename: Eunah
authors.initials: E
authors.lastname: Shin
authors.affiliation: Department of Pathology, Yonsei MokGu Clinic, Seosan, Korea.
authors.forename: Seok Woo
authors.initials: SW
authors.lastname: Yang
authors.affiliation: Thyroid Cancer Center, Department of Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Cheong Soo
authors.initials: CS
authors.lastname: Park
authors.affiliation: Thyroid Cancer Center, Department of Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Seok Mo
authors.initials: SM
authors.lastname: Kim
authors.affiliation: Department of Pathology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea. soonwonh@yuhs.ac.
authors.forename: Soonwon
authors.initials: S
authors.lastname: Hong
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology / Q000556:secondary; D000328:Adult; D018265:Carcinoma, Papillary, Follicular / Q000473:pathology / Q000556:secondary*; D005260:Female; D037502:Galectin 3 / Q000032:analysis; D006801:Humans; D006965:Hyperplasia / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D012888:Skull Neoplasms / Q000556:secondary*; D013964:Thyroid Neoplasms / Q000473:pathology*
chemical_list: D037502:Galectin 3
keywords: CD56, immunohistochemistry; adenomatous hyperplasia; extremely well-differentiated; follicular epithelial dysplasia; papillary thyroid carcinoma; well-differentiated tumors of uncertain malignant potential