Abstract
INTRODUCTION: Anaplastic sarcoma of the kidney (ASK) is a rare renal tumor, with fewer than 50 cases reported in the literature since 2007. ASK is pathologically characterized by the presence of cystic and solid areas consisting of spindle cells showing marked anaplasia. Recent studies have reported that the vast majority of patients with ASK have DICER1 variants, and that these tumors are part of the DICER1 syndrome, a hereditary cancer predisposition disorder. Herein, we report a pediatric case of this rare tumor, including pathological findings, DICER1 gene analysis of the tumor and peripheral blood samples, and the disease course. CASE PRESENTATION: A previously healthy 2-year-old girl presented with gross hematuria and a mass in her right abdomen. She had a family history of tumor; her eldest maternal aunt had developed rhabdomyosarcoma, another maternal aunt had follicular thyroid cancer, and her maternal grandmother had a benign thyroid tumor. Imaging revealed a 10-cm tumor with conspicuous internal cystic structures in the right kidney. The patient underwent right nephrectomy, removing a tumor measuring 12.5 × 9 × 8 cm that contained cystic and solid parts. The tumor was composed of spindle-shaped cells with anaplastic changes. Finally, the diagnosis of ASK was established. The treatment regimen, in accordance with the therapy for clear cell sarcoma of the kidney or diffuse anaplasia type Wilms tumor, was administered. Based on the diagnosis of ASK and the family history of DICER1-associated tumors, DICER1 syndrome was suspected. Sequencing of the hotspot region (i.e., RNase IIIb domain) using tumor specimen and coding regions using blood sample in the DICER1 revealed somatic c.5125G>A (p.D1709N) and germline c.4458dupA (p.S1487Ifs*5). Two years have passed since the end of treatment, and the patient is alive and healthy without evidence of tumor recurrence. CONCLUSIONS: Treatment with intensive chemotherapy (vincristine, doxorubicin, etoposide, and cyclophosphamide) and abdominal irradiation was effective as 2-year event-free survival was achieved. Since DICER1 syndrome causes a variety of rare cancers, particularly in infants and young adults, all surgeons and pediatric oncologists should be aware of the possibility of DICER1 syndrome.