[The clinicopathological features of adult thyroid tumors with DICER1 mutation]

A total of 37 cases of thyroid tumors with pathological features suggestive of DICER1 gene mutation were selected to detect the DICER1 gene and BRAF gene using Sanger sequencing. A total of 10 patients (27.0%) exhibited DICER1 gene mutation all of whom were female with an age of [M(Q₁, Q₃)] 38.0 (30.5, 47.5) years. All patients had wild-type BRAF^V600E gene. The ultrasound examination showed high-low echogenic well-demarcated intra-thyroidal nodules with abundant peripheral and internal blood flow signals in the DICER1 mutated thyroid tumor. The tumor was confined within the thyroid gland, with a diameter of (3.68±1.31) cm. The pathological features are as follows: the majority of tumors are encapsulated, which mainly composed of large follicles rich in colloid and some are small and micro follicles. The nucleus is round and deeply stained or slightly light stained, small to medium-sized, with occasional nuclear grooves and a lack of nuclear pseudoinclusion bodies within the nucleus. Immunohistochemical staining shows that Ki67 proliferation index of approximately 2%-10%. All cases were followed up for 11 to 18 months, and there was no recurrences or distant metastase. This study confirmed that the DICER1 gene mutation is mutually exclusive with the BRAF^V600E gene mutation. The thyroid tumor with DICER1 mutation are in big size and are more common in young females with a good prognosis. Cases with the wild-type DICER1 gene may exhibit similar morphological features, and molecular testing is recommended. If somatic DICER1 mutation is confirmed, patients should undergo germline mutation testing to rule out DICER1 syndrome in order to define whether genetic counseling is necessary.