Yonsei Med J.  2017 Jan;58(1):255-258. 10.3349/ymj.2017.58.1.255.

Extremely Well-Differentiated Papillary Thyroid Carcinoma Resembling Adenomatous Hyperplasia Can Metastasize to the Skull: A Case Report

• Pyo JY
• Kim J
• Choi SE
• Shin E
• Yang SW
• Park CS
• Kim SM
• Hong S

• KMID: 2374215
• DOI: http://doi.org/10.3349/ymj.2017.58.1.255

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.

Keyword

CD56, immunohistochemistry; papillary thyroid carcinoma; follicular epithelial dysplasia; adenomatous hyperplasia; extremely well-differentiated; well-differentiated tumors of uncertain malignant potential

MeSH Terms

Adenocarcinoma, Follicular/pathology/secondary
Adult
Carcinoma, Papillary, Follicular/pathology/*secondary
Female
Galectin 3/analysis
Humans
Hyperplasia/pathology
Lymphatic Metastasis
Male
Middle Aged
Neoplasm Recurrence, Local/pathology
Skull Neoplasms/*secondary
Thyroid Neoplasms/*pathology
Galectin 3

Figure

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  Fig. 1 Neck lymph node (LN) shows metastatic extremely well differentiated papillary thyroid carcinoma (EWD-PTC) (A, H-E stain, ×12.5 and inset ×400) with focal positivity of CK19 (B, ×400) in the first metastatic lesion. The left thyroid shows follicular variant papillary thyroid carcinoma (FVPTC) without capsular (arrow) invasion (C, H-E stain, ×40 and inset ×400) with focal positivity of CK19 (D, ×40) and loss of CD56 (E, ×40) in second episode. The LN also shows metastatic EWD-PTC (F, H-E stain, ×12.5 and inset ×400) with focal positivity of CK19 (G, ×400) and CD56 (H, ×400) in the second metastatic lesion. The skull lesion shows metastatic FVPTC (I, H-E stain, ×100 and inset ×400) with focal positivity of CK19 (J, ×400) and CD56 (K, ×400).

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