2018-19 Section 7-Neoplastic and Inflammatory Diseases of the Head and Neck eBook

Table 1. Malignancy rates before and after implementation of the histologic diagnostic category non-invasive follicular thyroid neo- plasmwith papillary-like nuclei in 3 studies used for meta-analysis Cases Malignancy rate before, % Malignancy rate after, % Strickland et al. [11] Non-diagnostic 53 18.9 17.0 Benign 167 13.2 5.4 FLUS 97 39.2 21.6 Follicular neoplasm 88 45.5 37.5 Suspicious for malignancy 94 87.2 45.7 Malignant 156 98.7 93.6 Total 655

up. An important component of the Bethesda categoriza- tion systemwas that each category was associated with an estimated range of malignancy risk. This linkage of diag- nostic category with malignancy risk was helpful in the follow-up management of patients with thyroid nodules. The risk of malignancy for each diagnostic category of TBSRTC was developed after a comprehensive literature search and was based on established histopathologic di- agnostic categories. The entity follicular variant of papil- lary thyroid carcinoma, including its invasive and non- invasive forms was included in the malignant category for the calculation of malignancy risk. Subsequent to the publication of TBSRTC, many authorities have come to view the non-invasive forms of follicular variant of papil- lary thyroid carcinomas as benign rather than malignant [2–8] . This reevaluation was based on substantial experi- ence that encapsulated/non-invasive forms of the follicu- lar variant of papillary thyroid carcinoma were unlikely to metastasize and generally behaved in a benign fashion [8] . For this reason, this subset of follicular-derived neo- plasms has been categorized as “non-invasive follicular thyroid neoplasm with papillary-like nuclear features,” (NIFTP) [2–8] . With this re-categorization of a signifi- cant number of neoplasms, originally considered histo- logically malignant to the histologically benign category, a change in the malignancy risk for the TBSRTC diagnos- tic categories is imminent [9, 10] . To evaluate the nature and size of this potential shift in malignancy risk, the au- thors studied the meta-analysis of the extant literature, investigating the changes in malignancy risk for the cyto- pathologic diagnostic categories secondary to changes in the histopathologic categorization of some non-invasive follicular variant papillary thyroid carcinomas as “be- nign.” The retrospective correlation study of material reviewed at the University of Missouri was submitted for Institutional Review Board assessment, and designated exempt by the University of Missouri Institutional Review Board. Following an electronic search of the records of the Division of Anatomic Pathology, 315 fine needle aspirates of the thyroid with surgical pathology follow- up were obtained for analysis. These cases had been classified using the 2008 Bethesda System for Reporting Thyroid Cytopathology [1] . The associated surgical pathology diagnoses were first ana- lyzed using the traditional categorization scheme where all follicu- lar variants of papillary thyroid carcinoma were considered malig- nant, and then reanalyzing the data for malignancy risk when the subset of follicular variants with encapsulation and non-invasive characteristics were considered benign [2, 7] . Material and Methods

Faquin et al. [10] Non-diagnostic

70 25.3 426 9.3 397 31.2 304 33.2 179 82.6 450 99.1

23.9 5.8 17.6 18.0 59.2 95.7

Benign FLUS

Follicular neoplasm Suspicious for malignancy

Malignant

Total

1,826

Layfield et al. (present study) Non-diagnostic

21 9.5 56 10.7 86 17.4 81 22.2 29 82.8 39 100

9.5 7.1

Benign FLUS

15.1 19.7 65.8 87.2

Follicular neoplasm Suspicious for malignancy

Malignant

Total

312

Canberk et al. [12] Non-diagnostic

202 13 1,296 7 98 45 127 30 69 72 94 98

6.5 6.0

Benign FLUS

30 10 48 87

Follicular neoplasm Suspicious for malignancy

Malignant

Total Original TBSRTC rate ranges Benign Follicular neoplasm Suspicious for malignancy FLUS

N/A

0–3

5–15 N/A 15–30 N/A 60–75 N/A

Malignant 97–99 N/A FLUS, follicular lesion of undetermined significance.

ria to select patients for fine-needle aspiration (FNA), techniques for procuring cytologic specimens, a report- ing format with diagnostic categories, and recommenda- tions for post-cytologic diagnosis, treatment, and follow-

Layfield/Baloch/Esebua/Kannuswamy/ Schmidt

Acta Cytologica 2017;61:187–193 DOI: 10.1159/000469654

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