Synchronous Ectopic Adrenal Rhabdomyosarcoma and Ipsilateral Cystic Nephroma Revealing a Diagnosis of DICER1-Related Tumor Predisposition: A Case Report.

DICER1-related tumor predisposition (DRTP) results from loss-of-function germline variants that predispose patients to numerous benign and malignant tumors. Cystic nephromas are among the most common neoplasms in patients with DRTP; however, there are no reports of rhabdomyosarcoma from adrenal tissue in children with DRTP. We present a case of a 30-month-old child with simultaneous cystic nephroma and rhabdomyosarcoma from ectopic adrenal tissue. He initially presented with chronic abdominal pain and poor weight gain. CT imaging demonstrated a large mass extending from the left kidney as well as an adjacent smaller mass in the retroperitoneum. Routine laboratory tests and tumor markers were unremarkable. He underwent an open left radical nephroureterectomy with excision of the midline retroperitoneal mass and lymph node dissection of the retrocaval and paraaortic basins. Pathologic examination revealed the larger mass to be a cystic nephroma, while the smaller mass was found to be embryonal rhabdomyosarcoma arising from ectopic adrenal tissue. Genetic testing of the rhabdomyosarcoma revealed a pathogenic c.4102dup (p.R1368fs) germline frameshift variant and a second c.5425G > A (p.G1809R) somatic missense variant in DICER1, as well as a somatic variant in BCOR. With this report, we advocate for further investigation of DICER1-associated rhabdomyosarcoma to improve management of this rare presentation.