Diagnosis of Thyroid Micropapillary Carcinoma and Histopathological Changes after Fine-needle Aspiration Biopsy

By Gizem Akkas Akgun¹, Sahinde Atlanoglu², Mehmet Korkmaz², Mehmet Fatih Ekici³, Mehmet Ali Gedik²

Affiliations

1. Department of Pathology, Kutahya Health Sciences University, Evliya Celebi Research and Training Hospital, Kutahya, Turkey
2. Department of Radiology, Kutahya Health Sciences University, Evliya Celebi Research and Training Hospital, Kutahya, Turkey
3. Department of General Surgery, Kutahya Health Sciences University, Evliya Celebi Research and Training Hospital, Kutahya, Turkey

doi: 10.29271/jcpsp.2022.04.445

ABSTRACT
Objective: To investigate “worrisome histologic alteration following fine-needle aspiration of the thyroid’’ (WHAFFT) in thyroid papillary microcarcinoma and the importance of tumor size, fibrosis, depth and concomitant diseases in ultrasonographic diagno
Place and Duration of Study: Department of Pathology, Kutahya Health Sciences University, Evliya Celebi Research and Training Hospital, Turkey, from December 2015 to December 2020.
Methodology: A total of 208 TPMC nodules belonging to 87 (41.8%) fine-needle aspiration biopsy (FNAB)-case group and 121 (58.2%) non-FNAB-control group were included in the study. The thyroidectomy specimens were evaluated for worrisome histologic alteration following fine-needle aspiration of the thyroid (WHAFFT). The relationship between tumor size, depth and capsule distance and concomitant diseases were investigated, according to the detection status in ultrasonography.
Results: In the FNAB group, hemorrhage, capsular distortion and tumor diameter were greater, while there was less non-tumor fibrosis and granulation tissue. Dysplasia focus was found to be higher in Hashimoto thyroiditis and lower in nodular goiter (p = 0.000). The rate of ≥0.5 cm tumors (p = 0.000), the rate of 0-25% tumor fibrosis (p = 0.038) and tumor-capsule distance between <0.2 cm (p = 0.030) was higher in thyroid micropapillary carcinomas detected in US. 
Conclusion: In the FNAB group, hemorrhage, capsular distortion and tumor diameter were greater. While fibrosis was insignificant in the diagnosis with ultrasonography (US), tumor size and location were found to be more significant. Since US has a lower success rate in lesions <0.5 cm and is deeply located, it can be supported with radiological alternatives.

Key Words: Worrisome histologic alteration, Thyroid micropapillary carcinoma, Fine-needle aspiration, Ultrasonography.

INTRODUCTION

In the last few decades, fine-needle aspiration biopsy (FNAB) has become a rapid, cost-effective and reliable diagnostic procedure in the evaluation of thyroid nodules.¹ In order to obtain efficiency from FNAB, the lesion must be detected by ultrasonography (US). The usefulness of US is controversial, especially in small lesions such as thyroid micropapillary carcinoma (TPMC) and also in deep lesions.²

 

FNAB procedure produces some histological and cytological changes in the thyroid gland. These changes are common and the concept of “worrisome histologic alterations following FNAB of thyroid (WHAFFT)’’, was first described by LiVolsi and Merino.¹ According to Pandit et al., WHAFFTs were seen in 38% of all specimens, and in 72% according to Rosemary et al.^3,4 Furthermore, problems may occur in diagnosis due to the above-mentioned histopathological findings caused by FNAB.^3,4 They may lead to misinterpretation of repeat FNAB, and the diagnosis of non-diagnostic or "insignificant follicular lesion atypia" (AUS/FLUS); and may require further repeat thyroid FNAB.^4,5 These diagnoses account for approximately 10% to 25% of all thyroid FNAB cases.⁴ However, it creates pitfalls in the diagnosis of repeated FNABs; and even tumor cells can be completely destroyed after FNAB is reported.^4,6

In this study, the aim was to compare WHAFFTs in TPMCs, incidentally detected on FNAB; and to evaluate the contribution and harms of FNAB method of diagnosis. The secondary aim was to investigate the importance of tumor size, capsule distance, fibrosis, existence of Hashimoto's thyroiditis and nodular goiter for evaluating the detection of the tumor ultrasonographically, which may affect the usefulness of FNAB in TPMC.

METHODOLOGY

This study included a total of 208 nodules consisting of 87 (41.8%) fine-needle aspiration biopsy (FNAB)-case group) and 121 (58.2%) non-FNAB-control group belonging to 132 patients, presenting to the Pathology Department, Kutahya Health Sciences University, Evliya Celebi Training and Research Hospital, Turkey between December 2015 and December 2020. HE sections of patients, who underwent thyroidectomy, were removed from the pathology archive.

The presence of hemorrhage, granulation tissue, siderophage, mitosis, granulomatous inflammation, capsular distortion, fibrosis, dysplasia, metaplasia, infarction, papillary hyperplasia and calcification was investigated as a WHAFFT component in the sections. It was checked whether there was a difference between FNAB and non-FNAB groups in terms of WHAFFT. While doing this, scoring was done for fibrosis detection. In the evaluation of fibrosis, intra-tumor and non-tumor areas were separately scored as 0-25 = I, 26-49 = II, 50-75 = III, and >76 = IV.

When looking at detection rates with ultrasonography (US), tumor size was divided into ≤0.5 and >0.5; and tumor capsule distance was divided into three as <0.2, 0.2-0.5, and >0.5 cm. From the past US reports of the cases, which nodules were detected with US or not was checked. In addition, whether there was a difference between the nodules detected and undetected in US in terms of size, fibrosis, tumor capsule distance, and the existence of Hashimoto's thyroiditis and nodular goiter was investigated. Diagnoses, according to Bethesda classification from past FNAB reports, were noted.⁵

To determine the usefulness of US and FNAB in small thyroid lesions, the authors included the thyroid papillary carcinoma cases smaller than 1 cm and excluded tumors larger than 1 cm. Twenty-five (12%) cases, whose US reports could not be accessed, were excluded. TPMC nodules, whose HE slides could not be reached, were excluded during the statistical evaluation.

Descriptives of quantitative variables were expressed as mean and SD for normally distributed variables, while as; median and range for not normally distributed variables. Counts and percentages were given for qualitative categorical variables. The conformity of data to normal distribution was examined using the Shapiro-Wilk test. The Mann-Whitney U-test was used to compare continuous data between independent variables of two groups. The Chi-square test and Fisher’s Exact test were used in the group comparisons (cross-tabulation) of nominal variables. IBM SPSS version 20 software package was used in statistical analyses, and p <0.05 was accepted as the statistical significance limit.

RESULTS

The mean age was 48.74 ± 11.68; 100 (75.8%) were females while 32 (24.2%) were males. Eighty-seven (41.8%) of 208 TPMC nodules of 132 cases were in the FNAB group and 121 (58.2%) of them were in the non-FNAB group. Thirty-eight (28.7%) of the cases had multifocality. Of the 87 biopsied nodules, 38 (43.7%) were located in the right lobe, 45 (51.7%) in the left lobe, and 4 (4.6%) in the isthmus. The median tumor diameter was 0.5 (0.1-1). The median (Min-Max) number of tumor biopsies and tumor diameters were 1 (1-4), and 0.5 (0.1-1), respectively.

While 56 (26.9%) of 208 TPMC nodules were detected in ultrasonography (US), 127 (61.1%) of them could not be detected in US, and US data of 25 (12%) cases could not be reached. Detection of tumor diameter, capsule distance and fibrosis (%) in ultrasonography are given in Table I. The rate of ≥0.5 cm tumors (p =0.000), tumor-capsule distance between <0.2 cm (p = 0.030), and the rate of 0-25% tumor fibrosis (p = 0.038) were higher in TPMCs detected in US. No statistical difference was found between the detection/no-detection rates in US in terms of nodular goiter and Hashimoto's thyroiditis (HT) (Table I). Median (Min-Max) values ​​of dysplastic focus, values ​​found in terms of detection/nondetection in US, and test statistics were 0 (0-3)/0 (0-4), U=1804.0, and p=0.010, respectively. 

The diagnoses of nodules biopsied according to the Bethesda classification were I: 12 (9.9%), II=49 (40.4%), III = 12 (9.9%), IV = 11 (9.0%), V = 33 (27.2%), and VI = 4 (3.6%). A statistical comparison could not be made due to the small number of tumor calcifications, and  infarctions. In the vicinity of the biopsied TPMCs, the rates of hemorrhage (p = 0.022), capsular distortion (p = 0.010) and larger tumor diameter (p =0.140) were higher and those of non-tumor fibrosis (p = 0.020), and granulation tissue (p = 0.022) were lower (Table II).

FNAB/non-FNAB ratios (n = 166) of atypia and dysplastic focus were 6 (3.6%)/19 (11.4%); 3 (1.8%)/6 (3.6%). No statistically significant relationship was found between them (p = 0.765/p = 0.105). There was no difference between the number of atypia and dysplastic focus and the number of biopsies (p = 0.376/p = 0.629).

During study, 5/8 (62.5%) of the cases of atypia and 25/27 (92.5%) of the cases with dysplastic focus were observed in HT (Figure I). The rate of finding dysplastic focus was higher in nodules with HT (X²=29.433, p = 0.000). No statistical difference was found in terms of atypia in HT (p = 1.000).

In the study, 3/8 (37.5%) of the cases of atypia and 2/27 (7.5) of the cases with dysplastic focus were observed in nodular guatr (NG). Dysplastic focus was found to be lower in nodules with NG (X²=23.940, p=0.000). No statistical difference was found in terms of atypia in NG (p = 0.313).

Table I: Detection of tumor diameter, tumor-capsule distance, tumor fibrosis (%), nodular guatr and Hashimoto thyroiditis in ultrasonography.

	Detection in US Negative		Detection in US Positive		Test statistic	p
	Say1	%	Say1	%	χ2
Tumor diameter (n=183)
<0.5   ≥0.5	74 53	58.3 41.7	14 42	25 75	17.230	0.000
Tumor-capsule distance (n=160)
<0.2   0.2-0.5   >0.5	51 56 3	46.4 50.9 2.7	33 15 2	66 30 4.0	6.090	0.030
Tumor fibrosis (%) (n=153)
0-20   25-49   50-75   >76	74 13 16 6	67.9 11.9 14.7 5.5	23 6 6 9	52.3 13.6 13.6 20.5	8.449	0.038
Nodular guatr (n=183)
Positive   Negative	81 46	63.8 36.2	32 24	57.1 42.9	0.725	0.395
Hashimoto thyroiditis (n=172)
Positive   Negative	40 81	33.1 66.9	24 27	47.1 52.9	3.458	0.177
US: Ultrasonography;  Chi-square / Fisher’s Exact test.

Figure 1: Dysplastic foci in Hashimoto's thyroiditis.

DISCUSSION

Fine needle aspiration biopsy (FNAB) is a highly effective and widely used method in the diagnosis of thyroid papillary carcinoma.¹ However, FNAB has a higher chance of detecting a lesion if it is larger than 1 cm, the possibility of success decreases in lesions smaller than 1 cm.⁷ Therefore, thyroid micropapillary carcinoma (TPMC) is mostly incidentally detected.⁸ In this study, most of them (58.2%) were detected incidentally.

FNAB can also cause some histological changes, secondary to trauma caused by the aspiration needle.^1-4 In the literature, various publications on the incidence of worrisome histologic alteration following fine-needle aspiration of the thyroid (WHAFFT) are available.^{1-4, 6-11}

In some studies, the most common change was infarction or necrosis.¹² In this study, infarction or necrosis was observed only in one (0.6%) case. In other studies, hemorrhage is reported to be the most common change among WHAFFT, followed by granulation tissue and siderophage.^1,2,10,11 In the present study, the rates of hemorrhage (p = 0.022), capsular distortion (p = 0.008) and larger tumor diameter (p = 0.140) were greater in the FNAB group but non-tumor fibrosis (p = 0.020), and granulation tissue (p = 0.022) were lower. In this study, consistent with the literature, the incidence of hemorrhage (p = 0.022) was higher in the FNAB group, while the incidence of granulation tissue (p = 0.022) was found to be lower in the FNAB group, contrary to the literature. The incidence of siderophagia was not statistically significant (p = 0.668).

In this study, the rate of reactive atypia was 19 (11.4%) in the non-FNAB group and 6 (3.6%) in the FNABs group. Although reactive atypia, due to FNAB, causes non-diagnostic results and insignificant follicular lesion atypia (AUS/FLUS) diagnoses and creates a differential diagnosis problem, the rate of reactive atypia was not statistically significant (p = 0.765). In the present study, AUS/FLUS ratio among all FNABs was 9.9%; which was consistent with the literature.^5,13

 Table II: Comparison of the study groups according to histopathological changes and FNAB, non-FNAB.

	Non-FNAB		FNAB		Test statistic
	n	%	n	%	X2	p
Tumor diameter (n=208)
<0.5	64	52.9	37	42.5	2.176	0.140
≥0.5	57	47.1	50	57.5
Tumor fibrosis (%) (n=177)
0-25	75	70.8	45	63.4	4.873	0.181
25-49	12	11.3	8	11.3
50-75	14	13.2	8	11.3
>76	5	4.7	10	14
Non-tumor fibrosis (n=177)
Positive	27	25.5	8	11.3	5.408	0.020
Negative	79	74.5	63	88.7
Hemorrhage (n = 164)
Positive	63	62.4	50	79.4	5.226	0.022
Negative	38	37.6	13	20.6
Capsular distortion (n =166)
Positive	21	20.6	25	39.1	6.700	0.010
Negative	81	79.4	39	60.9
Siderophage (n = 166)
Positive	18	17.6	13	20.3	0.184	0.668
Negative	84	82.4	51	79.7
Granulation tissue (n = 166)
Positive	26	25.5	7	10.9	5.229	0.022
Negative	76	74.5	57	89.1
Tumor calcification (n=165)
Positive	4	3.9	1	1.6	0.722	0.650
Negative	98	96.1	62	98.4
Non-tumor  calcification  (n=166)
Positive	9	8.8	7	10.9	0.202	0.653
Negative	93	91.2	57	89.1
Metaplasia (n = 166)
Positive	37	36.3	18	28.1	1.179	0.278
Negative	65	63.7	46	71.9
Papillary hyperplasia (n=166)
Positive	27	26.5	16	25	0.044	0.833
Negative	75	73.5	48	75
Edema (n = 166)
Positive	14	13.7	9	14.1	0.044	0.951
Negative	88	86.3	55	85.9
Granulomatous inflammation (n=166)
Positive	2	2.0	6	9.4	4.713	0.056
Negative	100	98	58	90.6
FNAB: Fine-needle aspiration biopsy.

Fibrosis and capsular distortion are the most common changes seen most frequently between three weeks and six months.^1,14 In thıs study, the incidence of capsular distortion of the biopsied TPMCs was significantly higher in the FNAB group (p <0.05). The rate of capsular distortion was 7.6% in the study by Pandit et al. and 14% in the study by Bolat et al. In this study, this rate was 39.1%, which was considerably higher than the other studies.^3,11 The reason for this is that this study was based on only TPMCs; and the TPMCs detected by US were higher in those with a tumor capsule distance of <0.2 cm (p=0.030). In the study by Bolat et al., fibrosis was detected in 66.0% of patients undergoing FNAB and only 15.3% of those without a history of FNAB.¹¹ In this study, there was no statistical difference between FNAB and non-FNAB groups in terms of tumor fibrosis, while non-tumor fibrosis were higher in the non-FNAB group (p <0.05). This made the authors think that this situation may be more related to Hashimoto's thyroiditis (HT). In this study, there was no statistical difference in the detection rates of HT cases in US, while 24 (37.5%) of HT cases could be detected in US, and 40 (62.5%) could not be detected.

When fibrosis is evident in non-tumor areas, such as HT, it may mask particularly small lesions. However, there are various publications stating that fibrosis in tumors increases the detectability of the lesion in US. According to Moon et al.,¹⁴ some malignancies may lack central vascularity due to fibrosis. In addition, Reading et al. reported that refractive shadow appearance was also associated with fibrosis.¹⁵ In the current study, tumor fibrosis rate between 0-25% was higher in TPMC detected on US (p <0.05). This contradicts the notion that fibrosis makes lesions more distinguishable on US. This suggests that in lesions smaller than 1 cm, size and location are much more significant than fibrosis in diagnosis on US. In addition, it may be necessary to use Doppler US to evaluate the lack of central vascularity^14,16 and high-resolution transducers.²

The number of dysplastic foci was lower among the TPMCs detected in US (p <0.05). This was associated with the higher incidence of dysplasia in HT and US details being masked by HT (p <0.001). In the literature, the presence of HT in the thyroid was reported to significantly decrease the sensitivity and specificity in nodules of <0.5 cm.¹⁷ Hashimoto's thyroiditis is the most common inflammatory thyroid disease, and the relationship between HT and TPC has a long history of debate, with no consensus having been reached on the link between these two thyroid diseases.^4,17,18

In the management of thyroid nodules ≤1 cm, the performance of US‐FNAB is widely debated. In 2016, the American Association of Clinical Endocrinologists recommends monitoring for nodules <5 mm, while ultrasound-FNAB is recommended for nodules >0.5 with suspicious sonographic features.¹⁹ In the literature, few reports comparing the efficacy of US-FNAB in thyroid nodules smaller than 0.5 cm in diameter have presented different results.¹⁹ Sabel et al. reported as the nodule becomes smaller, the NDS rate becomes higher and the sensitivity of the FNAB becomes lower.²⁰ In this study, 101 (48.6%) of the cases were below 0.5 cm and tumor diameters in the non-FNAB group were smaller than the FNAB group (p= <0.01).

CONCLUSION

In the FNAB group, hemorrhage, capsular distortion, and tumor diameter were greater; however, they did not affect the tumor diagnosis negatively. In the presence of Hashimoto's thyroiditis, it should be kept in mind that dysplastic foci may be missed by masking with non-tumor fibrosis on ultrasonography (US). Tumor fibrosis was found to be insignificant in the diagnosis with the US, but more significant in the diagnosis by size and location. Since US has a lower success rate in lesions < 0.5 cm and is deeply located, it can be supported with radiological alternatives.

ETHICAL APPROVAL:
Ethical approval was obtained from Non-Interventional Clinical Research Ethics Committee of the Kutahya Health Science University Evliya Celebi Research and Training Hospital, prior to the initiation of the research work (Date: 25.01.2021, Decision No. 2021/1744).

PATIENTS’ CONSENT:
Since it was a retrospective study, no patient consent form was obtained.

CONFLICT OF INTEREST:
The authors declared no conflict of interest.

AUTHORS’ CONTRIBUTION:
GAA, SA, MK, MFE, MAG: Substantial contributions to the conception or design of the work; and the acquisition, analysis or interpretation of data for the work. Final approval of the version to be published. Agreement to be accountable for all aspects of the work.
GAA: Drafting the work, and revising it critically for important intellectual content.

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