Follicular variant of papillary carcinoma of the thyroid: To what extent is fine-needle aspiration reliable?

Fine-needle aspiration of the thyroid: Rate and causes of cytohistopathologic discordance

“…This was mostly due to overdiagnosis of follicular neoplasm in 28 cases, predominantly because of overlapping cytologic criteria among hyperplastic adenomatous nodules in goiter, follicular adenomas, well-differentiated follicular carcinomas, and the follicular variant of papillary carcinomas. 10,11,[22][23][24][25][26] The presence of syncytial fragments and a microfollicular pattern strongly suggests a follicular cancer, but in 15-25% of cases, surgical resection will reveal a hyperplastic nodule. 12,17 The risk of malignancy with indeterminate cytology depends on the definition of the term and is reported as 15-20% of thyroid aspirates.…”

Second opinion in thyroid fine-needle aspiration biopsy by the Bethesda system

“…Forty-seven cases (3.1%) were diagnosed as Category IV in PD; however, 16 cases (1.1%) were diagnosed as Category IV in SOD. This difference was due to over-diagnosis in 20 cases (42.6%), predominantly due to overlapping cytologic criteria among hyperplastic adenomatous nodules in goiter, follicular adenomas, well-differentiated follicular carcinomas, and the follicular variant of papillary carcinomas [9,10,[27][28][29][30][31]. Limitations in the ability to further characterize follicular lesions on thyroid FNA have led to debates on management approaches.…”

Fine Needle Aspiration Biopsies of the Head and Neck: The Surgical Pathologist's Perspective

“…Unusual histologic subtypes of papillary, follicular, and medullary neoplasms are now recognized, which have the ability to simulate metastatic tumors, or even imitate one another. For example, it is now recognized that papillary carcinoma may assume a pure follicular pattern, as well as Hurthle-cell, "solid," clear-cell, tall-cell, columnar-cell, and nodular fasciitis-like forms [65][66][67][68][69][70][71][72]. Hyalinizing-trabecular adenoma demonstrates occasional nuclear inclusions that can mimic papillary carcinoma of the thyroid.…”