Follicular Variant of Papillary Thyroid Carcinoma
Although architecturally, it fits into the category of follicular neoplasm, follicular variant of papillary thyroid carcinoma is classified as a subtype of papillary carcinoma because it behaves clinically like papillary carcinoma. The tumor is comprised predominantly of follicles; however, the characteristic nuclear features of classic papillary carcinoma are present. Papillary clusters are notably absent. The most common diagnostic dilemma is mistaking it for either goiter or follicular neoplasm. This is due to the fact that there is an overlapping diagnostic criteria for follicular lesions in general and also the paucity of diagnostic features of PTC in this variant, either because they are poorly developed or present only focally. When the predominant architecture is the presence of syncytial tissue fragments, especially in a background of colloid, the lesion can be misdiagnosed as nodular goiter.
KeywordPapillary thyroid carcinoma Follicular variant Encapsulated Cytomorphology Architecture Microfollicles Syncytial tissue fragments Nuclear features RAS mutation Follicular neoplasm
- 14.Lloyd RV, Erickson LA, Casey MB, Lam KY, Lohse CM, Asa SL, Chan JK, DeLellis RA, Harach HR, Kakudo K, LiVolsi VA, Rosai J, Sebo TJ, Sobrinho-Simoes M, Wenig BM, Lae ME. Observer variation in the diagnosis of follicular variant of papillary thyroid carcinoma. Am J Surg Pathol. 2004;28:1336–40.CrossRefPubMedGoogle Scholar
- 15.Kini SR. Thyroid cytopathology: an Atlas and text. Philadelphia: Wolters Kluwer/ Lippincott Williams & Wilkins; 2008.Google Scholar
- 25.DeMay RM. The art and science of cytopathology: superficial aspiration cytology. Chicago: ASCP Press; 2012.Google Scholar
- 28.Chan JKC. Tumors of the thyroid and parathyroid glands. In: Fletcher CDM, editor. Diagnostic histopathology of tumors. 2nd ed. Edinburgh, Scotland: Churchill Livingstone; 2000. p. 959–1056.Google Scholar