J Korean Thyroid Assoc.  2012 Nov;5(2):104-108. 10.11106/jkta.2012.5.2.104.

Diagnostic Dilemma of a Follicular Lesions/Neoplasm in Thyroid Fine Needle Aspiration Cytology

• Jung CK

• KMID: 2095098
• DOI: http://doi.org/10.11106/jkta.2012.5.2.104

Abstract

Fine needle aspiration cytology (FNAC) of thyroid nodules is the best screening test for the selection of patients that may require surgical management. However, the diagnosis of follicular neoplasm on FNAC remains a gray area and the main differential diagnosis of follicular neoplasm includes benign (nodular hyperplasia and follicular adenoma) and malignant (follicular carcinoma and follicular variant of papillary carcinoma) lesions. The cytologic diagnosis of follicular neoplasm is based on the high cellularity, microfollicular or trabecular pattern, overlapping follicular cells, and scanty or absent colloid. Histologically, the diagnosis of follicular carcinoma requires the presence of tumor capsular invasion or vascular invasion. In the follicular variant of papillary carcinoma, nuclear features of papillary carcinoma may be subtle and seen in only a small number of cells, and thus may not be readily appreciated. Analyses of BRAF and RAS point mutations and RET/PTC and PAX8/PPARgamma rearrangements have been reported to be a useful ancillary tool for diagnosing thyroid cancer in cytology specimens. The presence of BRAF or RET/PTC mutation is a strong indicator of papillary carcinoma. PAX8/PPARgamma rearrangement is exclusively found in follicular carcinoma. RAS mutations are found in follicular adenoma/carcinoma and follicular variant of papillary carcinoma. Therefore, molecular testing of FNAC samples can improve the accuracy of cytologic diagnosis.

Keyword

Thyroid neoplasm; Fine-needle aspiration; Differential diagnosis; Molecular diagnostic testing

MeSH Terms

Biopsy, Fine-Needle
Carcinoma, Papillary
Colloids
Diagnosis, Differential
Humans
Hyperplasia
Mass Screening
Molecular Diagnostic Techniques
Point Mutation
Thyroid Gland
Thyroid Neoplasms
Thyroid Nodule
Colloids