Optimized Cutoff Value and Indication for Washout Thyroglobulin Level According to Ultrasound Findings in Patients with Well-Differentiated Thyroid Cancer

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Fig 1.
Ultrasonography of a 73-year-old man who had a small cystic nodule (A, cross) in the left thyroid gland and a suspicious cystic level VI lymph node (B, arrow). US-guided FNA cytology was performed on the small cystic thyroid nodule and the level VI cystic node, and the results were suspicious for papillary thyroid carcinoma from a nodule and a few pigmented macrophages from a lymph node. However, metastasis was considered due to the high FNA-Tg level of 1023 ng/mL. Final surgical pathology revealed a tiny papillary thyroid carcinoma of the left thyroid gland and nodal metastasis.
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Fig 2.
A 39-year-old female patient who underwent total thyroidectomy. The patient had a palpable lymph node (cross) in level V and no suspicious US feature. Even though the lymph node had inadequate FNA cytology due to a few hemosiderin-laden macrophage and lymphoid cells, it was considered benign because of its low FNA-Tg level. The node showed no changes in a 2-year follow-up. According to our results, there was no significant diagnostic enhancement of FNA-Tg in patients without suspicious US findings.
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Fig 3.
Flow chart of recommended management of clinically suspicious lymph nodes in patients with well-differentiated thyroid carcinoma from our results.

Table 1:

Clinical, imaging, and cytopathologic characteristics of 177 lymph nodes

Characteristics	Total (n = 177) (%)
Age (mean) (yr)	47 (range, 15–85)
Sex (female/male)	127:50
Mean lesion size (mean) (cm)	1.0 (range, 0.2–3.6)
Patient status
Preoperative	81 (46)
Postoperative	96 (54)
Suspicious malignant US features
Yes	109 (62)
No	68 (38)
Initial FNA
Malignant	66 (37)
Benign	94 (53)
Inadequate	17 (10)
Final cytopathology
Malignant	77 (44)
Benign	100 (56)
Reference standard
Surgical excision	81 (46)
Follow-up	96 (54)

Table 3:

Diagnostic performance of suspicious US findings for 177 lymph nodes^a

	Sensitivity	Specificity	PPV	NPV	Accuracy
Microcalcification	27.3 (21/77)	95.0 (95/100)	80.8 (21/26)	62.9 (95/151)	65.5 (116/177)
Cystic change	28.6 (22/77)	96.0 (96/100)	84.6 (22/26)	63.6 (96/151)	66.7 (118/177)
Hyperechoic cortex	42.9 (33/77)	89.0 (89/100)	75.0 (33/44)	66.9 (89/133)	68.9 (122/177)
Not oval shape	15.6 (12/77)	86.0 (86/100)	46.1 (12/26)	57.0 (86/151)	55.3 (98/177)
Irregular margin	26.0 (20/77)	95.0 (95/100)	80.0 (20/25)	62.5 (95/152)	65.0 (115/177)
At least 1 of US findings	96.1 (74/77)	65.0 (65/100)	67.9 (74/109)	95.6 (65/68)	78.5 (119/177)

Table 4:

Comparison of diagnostic performances of FNA-C and FNA-C with FNA-Tg according to US features using washout Tg ≥ 1.8^a

US Feature	Sensitivity	Specificity	PPV	NPV	Accuracy
Overall
FNA-C	84.4	99.0	98.5	89.2	92.1
FNA-C+FNA-Tg	100	93.0	91.7	100	96.1
P value	.0015^b	.04123^b	.0235^b	.0011^b	.2386
Positive
FNA-C	85.1	97.1	98.4	75.6	88.9
FNA-C+FNA-Tg	100	91.4	96.1	100	97.3
P value	.0051^b	.9590	.4149	.0088^b	.0530
Negative
FNA-C	66.7	100	100	98.5	98.5
FNA-C+FNA-Tg	100	93.9	42.9	100	61.7
P value	1.0000	.1336	02482	.3212	.3711