DICER1 encodes an RNase III endonuclease protein that regulates the production of small non-coding RNAs. Germline mutations in DICER1 are associated with an autosomal dominant hereditary cancer predisposition syndrome that confers an increased risk for the development of several rare childhood and adult-onset tumors, the most frequent of which include pleuropulmonary blastoma, ovarian sex cord-stromal tumors, cystic nephroma, and thyroid gland neoplasia. The majority of reported germline DICER1 mutations are truncating sequence-level alterations, suggesting that a loss-of-function type mechanism drives tumor formation in DICER1 syndrome. However, reports of patients with germline DICER1 whole gene deletions are limited, and thus far, only two have reported an association with tumor development. Here we report the clinical findings of three patients from two unrelated families with 14q32 deletions that encompass the DICER1 locus. The deletion identified in Family I is 1.4 Mb and was initially identified in a 6-year-old male referred for developmental delay, hypotonia, macrocephaly, obesity, and behavioral problems. Subsequent testing revealed that this deletion was inherited from his mother, who had a clinical history that included bilateral multinodular goiter and papillary thyroid carcinoma. The second deletion is 5.0 Mb and was identified in a 15-year-old female who presented with autism, coarse facial features, Sertoli-Leydig cell tumor, and Wilms' tumor. These findings provide additional supportive evidence that germline deletion of DICER1 confers an increased risk for DICER1-related tumor development, and provide new insight into the clinical significance of deletions involving the 14q32 region.

Sertoli-Leydig cell tumors are a group of tumors composed of variable proportions of Sertoli cells, Leydig cells, and sometimes heterologous elements. We describe the case of a 68-yr-old woman who presented with abdominal distention. A computed tomographic scan revealed a large right adnexal mass without evidence of intrahepatic tumors, and a complete cytoreductive surgery was performed. Pathologic examination revealed a moderately differentiated Sertoli-Leydig cell tumor with various heterologous elements, including gastrointestinal-type glands, insular carcinoid, and aggregations of hepatocytes without significant cytologic atypia. Moreover, adjacent to these hepatocytes, extensive overgrowth of highly atypical hepatocyte-like cells, providing a striking morphologic similarity to hepatocellular carcinoma of the liver, was identified. Both the heterologous hepatocytes and hepatocellular carcinomatous tumor cells were immunohistochemically positive for alpha-fetoprotein, hepatocyte paraffin 1, and arginase-1. Some Sertoli cells adjacent to the heterologous hepatocytes were also positive for alpha-fetoprotein and hepatocyte paraffin 1. The present case showed that a tumor morphologically and immunohistochemically analogous to hepatocellular carcinoma of the liver can arise in the ovary, in association with Sertoli-Leydig cell tumors.

Germline DICER1 pathogenic variants predispose to numerous benign and malignant tumors. In this report, we describe DICER1 gene analysis in an adolescent diagnosed with multinodular goiter, ovarian Sertoli-Leydig cell tumor, and lung cyst. DICER1 mutational screening at the DNA level failed to detect any pathogenic variant. Subsequent messenger RNA (mRNA) analysis revealed a 132 nucleotide intronic sequence exonization. This truncating event was caused by a deep intronic mutation generating a de novo acceptor splice site. This study demonstrates that some undetected DICER1 mutations should be investigated at the mRNA level.

Our report details the workup and management of a 43-year-old woman with an identical twin who presented with 2 years of virilization and secondary amenorrhea. Serum total testosterone was elevated. An MRI did not identify adnexal or adrenal pathology. Subsequent ovarian vein sampling demonstrated unilateral testosterone elevation. The patient underwent laparoscopic unilateral oophorectomy resulting in the diagnosis of Sertoli-Leydig cell tumor (SLCT). Although SLCT is a rare sex-cord ovarian tumor, it is associated with endometrial hyperplasia and malignancy. Our goals are to review the workup of androgen-secreting tumors and discuss the clinical importance of the DICER1 mutation in the context of SLCT. In this case, an identical twin underwent DICER1 testing which was one of the essential steps in her clinical management.

Pathogenic germline DICER1 variants cause a hereditary cancer predisposition syndrome with a variety of manifestations. In addition to conferring increased cancer risks for pleuropulmonary blastoma (PPB) and ovarian sex cord-stromal tumors, particularly Sertoli-Leydig cell tumor, individuals with pathogenic germline DICER1 variants may also develop lung cysts, cystic nephroma, renal sarcoma and Wilms tumor, nodular hyperplasia of the thyroid, nasal chondromesenchymal hamartoma, ciliary body medulloepithelioma, genitourinary embryonal rhabdomyosarcoma, and brain tumors including pineoblastoma and pituitary blastoma. In May 2016, the International PPB Registry convened the inaugural International DICER1 Symposium to develop consensus testing and surveillance and treatment recommendations. Attendees from North America, Europe, and Russia provided expert representation from the disciplines of pediatric oncology, endocrinology, genetics, genetic counseling, radiology, pediatric surgery, pathology, and clinical research. Recommendations are provided for genetic testing; prenatal management; and surveillance for DICER1-associated pulmonary, renal, gynecologic, thyroid, ophthalmologic, otolaryngologic, and central nervous system tumors and gastrointestinal polyps. Risk for most DICER1-associated neoplasms is highest in early childhood and decreases in adulthood. Individual and caregiver education and judicious imaging-based surveillance are the primary recommended approaches. These testing and surveillance recommendations reflect a consensus of expert opinion and current literature. As DICER1 research expands, guidelines for screening and treatment will continue to be updated. Clin Cancer Res; 24(10); 2251-61. ©2018 AACR.