Prevalence of DICER1 variants in large multinodular goiter: thyroid function, clinical and imaging characteristics

ABSTRACT Objective: Mutations in DICER1 are found in differentiated thyroid carcinoma (DTC) and in multinodular goiter (MNG) at a younger age with other tumors, which characterizes DICER1 syndrome. DICER1 is one driver to DTC; however, it is also found in benign nodules. We speculated that patients with mutations in DICER1 may present long-lasting MNG. Our aim was to investigate the frequency of DICER1 variants in patients with MNG. Subjects and methods: Patients who submitted to total thyroidectomy due to large MNG with symptoms were evaluated. DICER1 hotspots were sequenced from thyroid nodule samples. To confirm somatic mutation, DNA from peripheral blood was also analyzed. Results: Among 715 patients, 154 were evaluated with 56.2 ± 12.3 years old (28-79) and the thyroid volume was 115.7 ± 108 mL (16.2-730). We found 11% with six DICER1 variations in a homo or heterozygous state. Only rs12018992 was a somatic DICER1 variant. All remaining variants were synonymous and likely benign, according to the ClinVar database. The rs12018992 was previously described in an adolescent with DTC, measuring 13 mm. There were no significant differences according to gender, familial history of goiter, age, thyroid volume, TSH and TI-RADS classification between DICER1 carriers. Free T4 were lower in patients with DICER1 polymorphisms (13.77 ± 1.8 vs. 15.44 ± 2.4 pmol/L, p = 0.008), regardless of TSH levels. Conclusions: We conclude that germline DICER1 variants can be found in 11% of large goiters but no second-hit somatic mutation was found. DICER1 is one driver to thyroid lesion and a second-hit event seems unnecessary in the MNG development.

Pituitary blastoma, expanding the spectrum of newly recognized entities. A case report

Tumors of the pituitary gland and sellar region represent about 15% of all brain tumors, with pituitary adenoma being the commonest and pituitary carcinoma being very rare. Pituitary tumors in children are even rarer. Pituitary blastoma, a pediatric adenohypophysial tumor, is a new entity described in the 2017 WHO classification of pituitary tumors. This is a very rare tumor with only 21 cases reported so far. Hence, we are reporting this unusual case seen in a 7-month-old infant who presented with a large sellar/suprasellar mass with pressure symptoms of short duration. Typically, they present between 7–24 months of age. On histopathology, a cellular tumor was seen with primitive-looking round cells with scanty cytoplasm with few well-defined gland or rosette-like structures. The immunohistochemical stains showed diffuse strong staining for synaptophysin with a very high MIB-1 index. Other markers for common round cell tumors in this age group and hormonal markers of pituitary tumors were negative with INI-1 being intact. The initial cases described by Scheithauer presented with Cushing's disease and at least focally expressed adrenocorticotrophic hormone on immunohistochemistry. However, nonfunctioning tumors are also seen, albeit rarely. These are known to be associated with DICER 1 mutations and have a poor prognosis. Hence, morphologic recognition in the right clinical context and excluding other differential diagnoses in infants help make the correct diagnosis.

Conditional deletion of the human ortholog gene Dicer1 in Pax2-Cre expression domain impairs orofacial development.

Background: Orofacial clefts are common worldwide and result from insufficient growth and/or fusion during the genesis of the derivatives of the first pharyngeal arch and the frontonasal prominence. Recent studies in mice carrying conditional and tissue-specific deletions of the human ortholog Dicer1, an RNAse III family member, have highlighted its importance in cell survival, differentiation, proliferation, and morphogenesis. Nevertheless, information regarding Dicer1 and its dependent microRNAs (miRNAs) in mammalian palatogenesis and orofacial development is limited. Aims: To describe the craniofacial phenotype, gain insight into potential mechanisms underlying the orofacial defects in the Pax2-Cre/Dicer1 CKO mouse, and shed light on the role of Dicer1 in mammalian palatogenesis. Materials And Methods: Histological and molecular assays of wild type (WT) and Pax2-Cre/Dicer1 loxP/loxP (Dicer1 CKO) mice dissected tissues have been performed to characterize and analyze the orofacial dysmorphism in Pax2-Cre/Dicer1 loxP/loxP mouse. Results: Dicer1 CKO mice exhibit late embryonic lethality and severe craniofacial dysmorphism, including a secondary palatal cleft. Further analysis suggest that Dicer1 deletion neither impacts primary palatal development nor the initial stages of secondary palatal formation. Instead, Dicer1 is implicated in growth, differentiation, mineralization, and survival of cells in the lateral palatal shelves. Histological and molecular analysis demonstrates that secondary palatal development becomes morphologically arrested prior to mineralization around E13.5 with a significant increase in the expression levels of apoptotic markers (P < 0.01). Conclusions: Pax2-Cre-mediated Dicer1 deletion disrupts lateral palatal outgrowth and bone mineralization during palatal shelf development, therefore providing a mammalian model for investigating the role of miRNA-mediated signaling pathways during palatogenesis.