Summary and Analysis of Molecular Biological Changes, PD-L1 Immune Status and Clinicopathological Features of 78 Cases of Papillary Thyroid Carcinoma (<1 cm in Diameter) Combined With Lateral Cervical Lymph Node Metastasis.

To observe and analyze the variation status of BRAF, K-RAS, N-RAS, RET, TERT and PIK3CA genes and the expression of PD-L1 immune factors in patients with papillary thyroid carcinoma (<1 cm in diameter) combined with lateral cervical lymph node metastasis, and to further explore the potential relationship and significance between the above 7 indexes and clinical ultrasound pathology and multiple parameters of ER, PR, and KI-67 protein. Seventy-eight cases of papillary thyroid carcinoma (<1 cm in diameter) combined with lateral cervical lymph node metastasis diagnosed after the first treatment in Yantai Yuhuangding Hospital from April 1, 2013, to April 1, 2021, were retrospectively analyzed (another 102 cases were not included in this study due to incomplete information), and the relevant clinical ultrasonic pathologic data were collected. The tumor DNA was extracted and the mutations of BRAF, K-RAS, N-RAS, RET, TERT, and PIK3CA were analyzed by ARMS fluorescence quantitative PCR. The expressions of PD-L1, ER, PR, and KI-67 were detected by immunohistochemistry. There were 78 patients of papillary thyroid carcinoma (<1 cm in diameter) combined with lateral cervical lymph node metastasis, including 20 males (mean age: 32.75 y) and 58 females (mean age: 49.97 y). Other clinical ultrasound pathologic parameters include: (1) preoperative serological thyroid function analysis includes TSH, FT4, FT3, TGAB, ATPO, and TRAB. (2) Ultrasound abnormalities include calcification, aspect ratio ≥1, unclear boundary and irregular shape. (3) Pathologic image analysis included tumor size, capsule invasion, extraglandular strap muscle invasion, the number of lymph node metastasis and the expression of ER, PR, and KI-67. (4) Postoperative I131 treatment. Combined molecular detection showed that, in 78 cases, BRAF gene mutation was the most common (52 cases), followed by N-RAS gene mutation (30 cases), then K-RAS (12 cases), TERT (7 cases), and RET (4 cases), while PIK3CA gene was wild-type. BRAF and K-RAS gene mutations only appeared in female patients. The former was related to 7 parameters: patient sex ( P =0.000), onset age ( P =0.000), TSH ( P =0.000), ultrasonic aspect ratio ( P =0.030), tumor size ( P =0.002), ER ( P =0.000), and PR ( P =0.003). The latter was related to 5 parameters: sex ( P =0.000), onset age ( P =0.008), TSH ( P =0.018), TGAB ( P =0.049), and strap muscle invasion ( P =0.021). Only one case of N-RAS gene mutation was male, and the other 29 cases were female. It was related to 5 parameters: patient sex ( P =0.000), onset age ( P =0.001), TF4 ( P =0.027), strap muscle invasion ( P =0.048), and KI-67 index ( P =0.009). TERT gene mutation was slightly more in men (4 cases) than in women (3 cases), which was not only related to sex ( P =0.045), but also related to strap muscle invasion( P =0.013). The RET gene mutation was associated with capsule invasion ( P =0.031) and strap muscle invasion ( P =0.022). Single gene, double gene and triple gene mutations were found in 63 of 78 tumors: single gene mutations were found in 26 cases, among which BRAF gene mutations were the most common (17 cases). There were 32 cases of double gene mutation, and the simultaneous mutation of BRAF + N-RAS gene was the most common (25 cases). There were 5 cases of triple gene mutation, and the combined mutation of BRAF + N-RAS + TERT gene was the most common (2 cases). PD-L1 immune factor status showed that the positive expression rate of PD-L1 in 78 tumors was about 94.9% (74 cases), which was related to 4 parameters: patient sex ( P =0.000), onset age ( P =0.000), TSH ( P =0.036), and ER ( P =0.025). Among them, 17.9% (14 cases) were ≥ 50% strong positive, and all of them were female patients (accounting for 34.5% of female patients). Papillary thyroid carcinoma (<1 cm in diameter) combined with lateral cervical lymph node metastasis mainly occurs in young and middle-aged female (female: male = 2.9:1), but male patients are younger. In molecular genetics, 5 gene abnormalities of BRAF, K-RAS, N-RAS, RET, and TERT were detected, which can be manifested in 3 modes: single gene mutation, double gene mutation, and triple gene mutation. The tumors with double gene mutation and triple gene mutation may be more invasive. The above 5 gene mutations and PD-L1-mediated immune escape play an important role in the pathogenesis of papillary thyroid carcinoma (<1 cm in diameter) and lateral cervical lymph node metastasis, while the PIK3CA gene may not be involved in the pathogenesis of the tumor. BRAF, K-RAS, and N-RAS gene mutations were more common in female patients, while RET and TERT gene mutations were more common in male patients. Among them, patients with BRAF and K-RAS gene mutations are usually accompanied by positive expression of ER and PR, suggesting that these patients may benefit from endocrine therapy. In addition, PD-L1-mediated immunotherapy has broad application prospects in this tumor, female patients may benefit more, and immunotherapy combined with endocrine therapy is expected to become a good adjuvant treatment option for female cases.