J Pathol Transl Med.  2020 May;54(3):197-203. 10.4132/jptm.2020.04.29.

New insights into classification and risk stratification of encapsulated thyroid tumors with a predominantly papillary architecture

• Jung CK
• Park SY
• Kim JH
• Kakudo K

• KMID: 2501654
• DOI: http://doi.org/10.4132/jptm.2020.04.29

Figure

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  Fig. 1. Noninvasive encapsulated papillary RAS-like thyroid tumor. (A) The tumor has a thick fibrous capsule and shows cystic change. (B) The solid area is predominantly composed of papillary architecture lined by cuboidal to columnar follicular cells. (C) Psammoma bodies are occasionally seen (arrow). (D) Tumor cells show nuclear enlargement, overlapping, and elongation, with slightly irregular nuclear membranes and dark chromatin, and have no nuclear pseudoinclusions. Molecular analysis revealed KRAS G12V mutation.

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  Fig. 2. Follicular adenoma with papillary hyperplasia. The tumor is cystic and has a thick complete capsule upon gross (A) and microscopic examination (B). (C) The tumor is composed of a predominantly papillary structure. (D) Tumor cells show basally located, small, and dark nuclei with round contours.

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  Fig. 3. Noninvasive encapsulated classic papillary thyroid carcinoma with predominant follicular growth and BRAF V600E. This tumor was initially misdiagnosed as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). (A) The tumor is completely surrounded by a thin fibrotic capsule. (B) The encapsulated tumor is composed of follicular architecture. (C) The tumor cells have florid nuclear features of papillary carcinoma. Nuclear pseudoinclusions and grooves are frequently seen. (D) Immunostaining for BRAF V600E (VE1) is positive.

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  Fig. 4. Two cases of the invasive form of noninvasive encapsulated papillary RAS-like thyroid tumor. (A, B) A tumor with NRAS Q61R. (C, D) The other case without BRAF V600E or RAS mutations. Both tumors show capsular invasion (A, C). A high-power view of the tumors reveals enlarged round-to-ovoid, overlapping nuclei with few nuclear grooves and less chromatin clearing than seen in classic papillary carcinoma.

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