Ultrasound gray scale ratio for differential diagnosis of papillary thyroid microcarcinoma from benign micronodule in patients with Hashimoto's thyroiditis

Abstract

Background: To investigate the diagnostic value of ultrasound gray scale ratio (UGSR) in differentiating papillary thyroid microcarcinomas (PTMCs) from benign micronodules (BMNs) in patients with Hashimoto's thyroiditis (HT).

Methods: The ultrasound images of 285 PTMCs (from 247 patients) and 173 BMNs (from 140 patients) in the HT group, as well as 461 PTMCs (from 417 patients) and 234 BMNs (from 197 patients) in the non-HT group were retrospectively analyzed. The diagnosis of all cases was confirmed by histopathological examinations. The gray scale values of the nodules and surrounding thyroid tissues were measured and subsequently the UGSRs were calculated. Receiver operating characteristic curve analysis was used to determine the area under the curve (AUC), optimal UGSR threshold, sensitivity and specificity in differentiating PTMCs and BMNs in the two groups.

Results: The UGSR of PTMC and BMN was 0.52 ± 0.12 and 0.85 ± 0.24 in the HT group (P < 0.001), and 0.57 ± 0.13 and 0.87 ± 0.20 in the non-HT group (P < 0.001), respectively. The difference in PTMC-UGSR was significant between the two groups (P < 0.001), whereas BMN-UGSR did not differ between the two groups (P = 0.416). The AUC, optimal UGSR threshold, sensitivity and specificity of UGSR for differentiating PTMC and BMN in the HT and non-HT group were 0.890 versus 0.901, 0.68 versus 0.72, 91.23% versus 90.67%, and 77.46% versus 82.05%, respectively.

Conclusions: The USGR of the HT group was lower than that of the non-HT group. Moreover, UGSR exhibited important diagnostic value in differentiating PTMC from BMN in both HT and non-HT groups.

Keywords: Echogenicity; Hashimoto’s thyroiditis; Papillary thyroid microcarcinoma; Thyroid nodule; ultrasound gray scale ratio.

Fig. 1

Flow chart of study participant selection

Fig. 2

A 39-year-old man with PTMC in the left lobe of the thyroid. A the ultrasound transverse image shows that UGSR is 0.51 (36.52/71.62). B the pathological image (H&E × 40 magnification) illustrates that the PTMC is located in the left upper part of the image, with high amounts of fiber and collagen hyperplasia (blue stars) inside the lesion, and almost no lymphocyte infiltration. The lesion and surrounding normal thyroid tissues are separated by fibers and minimal lymphocyte infiltration (black star)

Fig. 3

A 54-year-old woman with BMN in the left lobe of the thyroid. A the measurement is performed after avoiding the anechoic cystic region. The ultrasound longitudinal image shows that UGSR is 1.09 (74.09/67.79); B the pathological image (H&E × 40 magnification) indicates the presence of nodular goiter. The lesion is at the lower part of the image, which is separated from the normal thyroid tissues by fine fibers. Almost no lymphocyte infiltration is found within and around the lesion

Fig. 4

A 33-year-old woman with HT and PTMC in the left lobe of the thyroid. A calcification with hyperecho intensity is avoided during the measurement, and the ultrasound transverse image shows that UGSR is 0.27 (17.53/65.63). B the pathological image (H&E × 40 magnification) indicates the presence of HT accompanied with PTMC. The right part of the image corresponds to the PTMC, in which local fiber hyperplasia and moderate amount of lymphocyte infiltration are observed (black stars), and high amount of lymphocytes infiltration (black arrows) and lymphoid follicles formation are found around the lesion

Fig. 5

A 30-year-old woman with HT and BMN in the left lobe of the thyroid. A calcification with hyperecho intensity is avoided during the measurement. The ultrasound longitudinal image shows that UGSR is 0.88 (53.38/60.95). B the pathological image (H&E × 40 magnification) demonstrates the presence of accompanied with nodular goiter. The right part of the image corresponds to the nodular goiter, in which high amount of lymphocyte infiltration (yellow arrows) and lymphoid follicles formation (white stars) are observed. The lesion is separated from the surrounding tissues by relatively thick fibers, which are infiltrated with moderate amount of lymphocytes (black stars). Deep infiltration of the fibers is noted in the lesion, which is surrounded with high amount of lymphocyte infiltration (black arrows)

Fig. 6

A 49-year-old woman with HT and PTMC in the right lobe of the thyroid. A the hyperecho strap resulting from technical factors is avoided (white arrow). The ultrasound longitudinal image shows that UGSR is 0.22 (12.68/58.84). B the pathological image (H&E × 10 magnification) indicates the presence of HT accompanied with PTMC. PTMC is localized at the lower part of the image and depicted in the black square at the right lower part of the image (H&E × 100 magnification). The lesion is separated from the surrounding thyroid tissues by thick fibers and collagens, and high amount of lymphocyte infiltration (yellow arrows) is noted in the lesion. The magnified image at the right lower part indicates high amount lymphocyte infiltration in the central axis of the papilla and around the lesion (black arrows)

Fig. 7

A 37-year-old woman with HT and PTMC in the left lobe of the thyroid. 6A. The hyperecho strap (white arrow) resulting from technical factors is avoided. The ultrasound longitudinal image shows that the UGSR is 0.42 (40.42/96.75). 6B, The pathological image (H&E × 40 magnification) indicates the presence of HT accompanied with PTMC. PTMC is at the right part of the image. Low amount of lymphocyte infiltration and fiber hyperplasia are found in the lesion (yellow arrow), and high amount lymphocyte infiltration and lymphoid follicles formation are found around the lesion (black stars)

Fig. 8

ROC curves of UGSR for the differential diagnosis of PTMC from BMN in the two groups. A ROC curve for the HT group. B ROC curve for the non-HT group