Encapsulated follicular thyroid tumor with equivocal nuclear changes, so-called well-differentiated tumor of uncertain malignant potential: a morphological, immunohistochemical, and molecular appraisal.

Abstract

There is a continuous debate regarding the classification of thyroid follicular lesions and the term "well-differentiated tumor of uncertain malignant potential (WDT-UMP)" was recently introduced to cover this problematic spectrum of tumors. The objective of this study was to reappraise WDT-UMP using morphological, immunochemical, and molecular analysis and to shed more light on encapsulated thyroid follicular-patterned tumors. A total of 30 cases of WDT-UMP with equivocal papillary thyroid carcinoma-type nuclear changes (PTC-N) or focal unequivocal PTC-N were examined. As a control, follicular adenoma (n = 29), follicular carcinoma (n = 8), hyalinizing trabecular adenoma (n = 5), and PTC (n = 48) were included. HBME-1, cytokeratin 19, and galectin-3 were positive in 12 (40.0%), 10 (33.3%) and 11 (36.7%) cases of WDT-UMP, respectively. According to the positivity of those markers, significant differences were obtained between WDT-UMP and PTC encapsulated common type (P = 0.028, 0.010, and 0.004, respectively), infiltrative follicular variant (P = 0.020, 0.026, and 0.008, respectively), and infiltrative common type (P = 0.004, 0.001, and 0.005, respectively), but not between WDT-UMP and follicular adenoma or follicular carcinoma. BRAF(V600E) mutation was absent but RET/PTC1 rearrangement was found in only two (6.7%) cases of WDT-UMP. None of the 20 patients with WDT-UMP developed recurrence, with an average follow-up of 80 months. These findings indicate that WDT-UMP has a favorable outcome and is distinct from PTC in morphological, immunohistochemical, and molecular characteristics. We propose that WDT-UMP should be classified as "well-differentiated tumor with uncertain behavior".

• Authors: Zhiyan Liu, Gengyin Zhou, Misa Nakamura, Eisuke Koike, Yaqiong Li, Takashi Ozaki, Ichiro Mori, Emiko Taniguchi, Kennichi Kakudo
• Journal: Cancer science (Cancer Sci) Vol. 102 Issue 1 Pg. 288-94 (Jan 2011) ISSN: 1349-7006 [Electronic] England
• PMID: 21070478 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2010 Japanese Cancer Association.

Chemical References

• Biomarkers, Tumor
• Galectin 3
• HBME-1 antigen
• Keratin-19

Topics

• Adenocarcinoma, Follicular (chemistry, pathology)
• Adult
• Aged
• Aged, 80 and over
• Biomarkers, Tumor (analysis)
• Cell Differentiation
• Cell Nucleus (pathology)
• Female
• Galectin 3 (analysis)
• Humans
• Immunohistochemistry
• Keratin-19 (analysis)
• Male
• Middle Aged
• Thyroid Neoplasms (chemistry, pathology)