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DICER1 syndrome is a highly pleiotropic tumor predisposition syndrome that has been increasingly recognized in the last 10 years. Diseases in the syndrome result from mutations in both copies of the gene DICER1, a highly conserved gene that is critically implicated in micro-ribonucleic acid (miRNA) biogenesis and hence modulation of messenger RNAs. In general, susceptible individuals carry an inherited germline mutation that disables one copy of DICER1; within tumors, a very characteristic second mutation alters function of the other gene copy. About 20 hamartomatous, hyperplastic or neoplastic conditions comprise DICER1 syndrome. Most are not life-threatening, but some are aggressive malignancies. There are many unaffected carriers because penetrance is generally low; however, clinically occult thyroid nodules and lung cysts are frequent. Rare diseases of early childhood were the first recognized conditions in DICER1 syndrome, while other conditions affect adolescents and adults. The hallmarks of DICER1 syndrome are certain rare tumors including pleuropulmonary blastoma; cystic nephroma; ovarian Sertoli-Leydig cell tumor; sarcomas of the cervix, kidneys and cerebrum; pituitary blastoma; ciliary body medulloepithelioma; and nasal chondromesenchymal hamartoma. Radiologists are often the first practitioners to observe these diverse manifestations and play a primary role in recognizing DICER1 syndrome. [ABSTRACT FROM AUTHOR]

Dicer is central to microRNA-mediated silencing and several other RNA interference phenomena that are profoundly embedded in cancer gene networks. Most recently, both germline and somatic mutations in DICER1 have been identified in diverse types of cancer. Although some of the mutations clearly reduce the dosage of this key enzyme, others dictate surprisingly specific changes in select classes of small RNAs. This Review reflects on the molecular properties of the Dicer enzymes in small RNA silencing pathways, and rationalizes the newly discovered mutations on the basis of the activities and functions of its determinants. [ABSTRACT FROM AUTHOR]

The discovery of each new cancer susceptibility gene answers one set of questions but poses many more. In this article, we outline a recent example: a new cancer syndrome caused by germline mutations in DICER1, responsible for microRNA processing. In particular, we discuss the endocrine manifestations of mutations in this crucial gene. [Copyright &y& Elsevier]

The article discusses the association of germline DICER1 mutation with loss of heterozygosity in pineoblastoma. It explores the link between the loss of heterozygosity and tumor aggressiveness, and suggests that the complete loss of DICER1 protein offers a selective advantage to tumour cells that have undergone tumourigenesis. Moreover, it indicates the role of DICER1 mutations in the justification of rare tumours in the absence of family history of other cancers and related disorders.

Abstract: Objective: Pleuropulmonary blastoma (PPB) is a childhood cancer arising from pleuropulmonary mesenchyme. This neoplasm is a sentinel disease in a familial tumor syndrome recently found to be associated with germline mutations in DICER1. Observations of ovarian sex cord-stromal tumors (OSCST) in PPB kindreds led to further study. We sought to characterize ovarian tumors seen in probands and families with PPB and PPB-related conditions and define germline DICER1 status. Methods: Patient and family records of pathology-reviewed PPB cases enrolled in the International PPB Registry (IPPBR) were searched for ovarian tumors. Ovarian tumor pathology specimens were obtained and centrally reviewed. Germline DNA from patients with ovarian tumors was tested for DICER1 mutations. Three additional OSCST patients registered in the IPPBR were also tested for mutations in DICER1. Results: Among 296 kindreds including 325 children with PPB, we observed three children with both PPB and Sertoli–Leydig cell tumors (SLCT)/Sertoli cell tumors. Among family members of PPB patients, we identified six OSCST (three SLCT, one Sertoli cell tumor, one juvenile granulosa cell tumor, one gynandroblastoma). Age at ovarian tumor diagnosis was youngest in PPB probands and younger in family members than in OSCST in general. Germline DICER1 mutations were identified in four of six patients with OSCST from PPB kindreds and in two of three children with OSCST and no personal or family history of PPB. Conclusions: Primary ovarian neoplasms, particularly OSCST, are a manifestation of the familial PPB syndrome and may be the initial clinical presentation of DICER1 mutations within a family. [Copyright &y& Elsevier]