Thyroid nodules with FNA cytology suspicious for follicular variant of papillary thyroid carcinoma: Follow-up and management

Abstract

Thyroid nodules diagnosed as follicular neoplasm on fine‐needle aspiration biopsy (FNAB) may represent hyperplastic/adenomatous nodules, follicular adenoma or carcinoma, and follicular variants of papillary thyroid carcinoma (FVPTC) on histologic follow‐up. In our laboratory, we attempted to identify a subset of cases which showed cellular specimens with focal features (nuclear chromatin clearing, membrane thickening, and rare grooves) suspicious for the follicular variant of papillary thyroid carcinoma. These cases are reported as follicular‐derived neoplasms with nuclear features suspicious for FVPTC to distinguish them from those diagnosed as follicular neoplasm. This study documents our experience with 52 cases so diagnosed and followed prospectively with histologic follow‐up. A neoplastic nodule was confirmed in 45/52 cases (86%), of which 40 were malignant (77%). FVPTC was identified in 35/52 cases (67%). Four cases were usual papillary carcinoma, 3 were follicular adenoma, 2 were Hürthle‐cell adenoma, and 1 was insular carcinoma. In 7 cases, the subsequent histologic findings were nonneoplastic (5 hyperplastic nodules and 2 colloid nodules). Our prospective study shows that in cellular smears from thyroid nodules, a careful search for the nuclear features of papillary carcinoma should be performed, and it is appropriate to diagnose cases as suspicious for FVPTC if the nuclear features of papillary carcinoma are focal. The surgical management of this group may include an intraoperative confirmation of cytologic diagnosis by scrape preparation and/or frozen section in order to avoid a second surgical intervention for completion thyroidectomy. Diagn. Cytopathol. 2000; 23:380–385. © 2000 Wiley‐Liss, Inc.

Sonographically guided fine needle aspiration of thyroid nodule: Discrepancies between cytologic and histopathologic findings

“…In addition, FNA can be limited in the case of follicular neoplasm. 15,16 The false-positive rate was 11.6% (14/121) in our study. This is slightly higher than other recently reported false-positive rates ranging from 4% to 8%.…”

“…Because these cytologic findings occurred in a follicular adenoma, follicular carcinoma, nodular hyperplasia, and follicular variant of a papillary carcinoma, it is not possible to clearly differentiate them cytologically, 11,14 and a surgical excision is recommended for a definite pathologic diagnosis. 15,19 In our study, 14 (14.4%) of the 97 US-guided FNAs whose results were described as follicular or Hurthle cell neoplasms were pathologically malignant on permanent section. This is similar to the estimated 10-20% malignancy rate in indeterminate thyroid aspirates reported in the literature.…”

“…Because such invasion cannot be diagnosed with FNA, aspirates showing follicular or Hurthle cell neoplasm were considered indeterminate for a malignancy. 15,19 After surgery, all the final histopathologic diagnoses of thyroid nodules were categorized as benign (including nodular hyperplasia, follicular or Hurthle cell adenoma, and Hashimoto's thyroiditis) or malignant (including papillary, medullary, anaplastic, follicular, and Hurthle cell carcinomas).…”

“…[10][11][12][13][14] In addition, the distinction between a follicular malignancy, such as a follicular carcinoma or a follicular variant of papillary carcinoma, from benign lesions, such as a follicular adenoma or nodular adenomatous goiter, is very limited on cytologic grounds. 15,16 In this study, we analyzed our results of US-guided FNA of thyroid nodules and focused on the discrepancies between cytologic and final pathologic results.…”

The Bethesda System for Reporting Thyroid Cytopathology: Interpretation and Guidelines in Surgical Treatment

“…Such cases are best classified as suspicious for malignancy. Most (60-75%) of these cases prove to be papillary carcinomas and the rest are usually FAs [3,5,8].…”