Description of longitudinal tumor evolution in a case of multiply relapsed clear cell sarcoma of the kidney.

Background: Clear cell sarcoma of the kidney (CCSK) is the second most common pediatric renal tumor.

Case: A 2-year-old boy was diagnosed with CCSK, which relapsed four times until he yielded to the disease at the age of 7 years. To characterize the longitudinal genetic alterations occurring in the present case, we performed targeted-capture sequencing by pediatric solid tumors panel (381 genes) for longitudinally sampled tumors, including autopsy samples of metastasis. Internal tandem duplication of BCOR (BCOR-ITD) was the only truncal mutation, confirming the previously reported role of BCOR-ITD in CCSK.

Conclusion: Acquisition of additional mutations along tumor relapses and detection of metastasis-specific mutations were reminiscent of the tumor progression and therapeutic resistance of this case, leading to clonal selection and a dismal fate.