Objective: The encapsulated follicular variant of papillary carcinoma (FVPC) was recently reported to have genetic alterations and biological behavior closer to follicular adenoma/carcinoma than classic papillary carcinoma and unencapsulated FVPC. The objective of this study is to alert cytologists to this new subtype and to report our experience. Study Design: Cytology of 41 cases of surgery-proven encapsulated FVPC was reviewed and correlated with histopathology and ultrasound findings. These cases were collected over 19 years from 188 aspirates reported as ‘suspicious or atypical, cannot exclude FVPC’ and from 245 aspirates reported as follicular neoplasm. Results: Thirteen aspirates had diffusely atypical nuclei, 20 aspirates had mixed normal and atypical nuclei, and 8 aspirates had no atypical nuclei. On histology, papillary nuclei were distributed focally in the second and third groups. Crowded, oval, clear nuclei occurred in nearly 80% of the cases, nuclear grooves occurred in 12.2%, and nuclear pseudoinclusions occurred in 4.9%. Capsular invasion without angioinvasion was present in 30% of encapsulated FVPCs, with angioinvasion in 17.5% and lymph node metastasis in 7.5%. Most encapsulated FVPCs were benign-appearing on ultrasound with round-to-oval, circumscribed nodules with a hypoechoic rim. Conclusions: Encapsulated FVPC is more difficult to recognize on fine-needle aspiration and ultrasound than unencapsulated FVPC.

Baloch ZW, LiVolsi VA: Encapsulated follicular variant of papillary thyroid carcinoma with bone metastases. Mod Pathol 2000;13:861–865.
Chan JK: Strict criteria should be applied in the diagnosis of encapsulated follicular variant of papillary thyroid carcinoma (editorial). Am J Clin Pathol 2002;117:16–18.
Williams ED: Guest editorial: two proposals regarding the terminology of thyroid tumors. Int J Surg Pathol 2000;8:181–183.
Castro P, Rebocho AP, Soares RJ, et al: PAX8-PPARgamma rearrangement is frequently detected in the follicular variant of papillary thyroid carcinoma. J Clin Endocrinol Metab 2006;91:213–220.
Rivera M, Ricarte-Filho J, Knauf J, et al: Molecular genotyping of papillary thyroid carcinoma follicular variant according to its histological subtypes (encapsulated vs. infiltrative) reveals distinct BRAF and RAS mutation patterns. Mod Pathol 2010;23:1191–1200.
Rivera M, Tuttle RM, Patel S, Shaha A, Shah JP, Ghossein RA: Encapsulated papillary thyroid carcinoma: a clinico-pathologic study of 106 cases with emphasis on its morphologic subtypes (histologic growth pattern). Thyroid 2009;19:119–127.
Ghossein RA: Encapsulated malignant follicular cell-derived tumors. Endocr Pathol 2010;21:212–218.
Baloch ZW, Shafique K, Flannagan M, LiVolsi VA: Encapsulated classic and follicular variants of papillary thyroid carcinoma: comparative clinicopathologic study. Endocr Pract 2010;16:952–959.
Gallagher J, Oertel YC, Oertel JE: Follicular variant of papillary carcinoma of the thyroid: fine-needle aspirates with histologic correlation. Diagn Cytopathol 1997;16:207–213.
Baloch ZW, Gupta PK, Yu GH, Sack MJ, LiVolsi VA: Follicular variant of papillary carcinoma: cytologic and histologic correlation. Am J Clin Pathol 1999;111:216–222.
Logani S, Gupta PK, LiVolsi VA, Mandel S, Baloch ZW: Thyroid nodules with fine-needle aspiration cytology suspicious for follicular variant of papillary thyroid carcinoma: follow-up and management. Diagn Cytopathol 2000;23:380–385.
Fulciniti F, Benincasa G, Vetrani A, Palombini L: Follicular variant of papillary carcinoma: cytologic findings on fine needle aspiration biopsy samples – experience with 16 cases. Diagn Cytopathol 2001;25:86–93.
Wu HH, Jones JN, Grzybicki DM, Elsheikh TM: Sensitive cytologic criteria for the identification of follicular variant of papillary thyroid carcinoma in fine-needle aspiration biopsy. Diagn Cytopathol 2003;29:262–266.
Yang GC, Liebeskind D, Messina AV: Diagnostic accuracy of follicular variant of papillary thyroid carcinoma in fine-needle aspirates processed by Ultrafast Papanicolaou stain: histologic follow-up of 125 cases. Cancer 2006;108:174–179.
Eyibilen A, Aladağ I, Güven M, Köseoğlu RD: Surgical approach to encapsulated follicular variant of papillary thyroid carcinoma: a report of three cases (in Turkish). Kulak Burun Bogaz Ihtis Derg 2008;18:384–388.
Yang GC, Liebeskind D, Messina AV: Ultrasound-guided fine needle aspiration of the thyroid assessed by Ultrafast papanicolaou stain: data from 1,135 biopsies with a two- to six-year follow-up. Thyroid 2001;11:581–589.
Yang GC, Alvarez II: Ultrafast Papanicolaou stain: an alternative preparation for fine-needle aspiration cytology. Acta Cytol 1995;39:55–60.
Yang GC, Greenebaum E: Clear nuclei of papillary thyroid carcinoma conspicuous in fine needle aspiration and intraoperative smears processed by Ultrafast Papanicolaou stain. Mod Pathol 1997;10:552–555.
Baloch ZW, LiVolsi VA, Asa SL, et al: Diagnostic terminology and morphologic criteria for cytologic diagnosis of thyroid lesions: a synopsis of the National Cancer Institute Thyroid Fine-Needle Aspiration State of the Science Conference. Diagn Cytopathol 2008;36:425–37.
Ali SZ, Cibas ES: The Bethesda System for Reporting Thyroid Cytopathology: Definitions, Criteria, and Explanatory Notes. New York, Springer, 2010.
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