An Asymptomatic, Ectopic Mass As a Presentation of Adrenocortical Carcinoma Due to a Novel Germline P.Phe338Leu Tetramerisation Domain Variant

Adrenocortical carcinoma (ACC) is a rare cancer in childhood. ACC is frequently associated with germline variants, with founder effects especially due to the p.Arg337His mutation. ACC leads to the secretion of adrenocortical hormones, resulting in endocrine syndromes, which is the usual trigger for establishing the diagnosis. We present a surprising ACC pathology in a non-secreting, ectopic retroperitoneal tumour in a 4-year-old boy, successfully controlled with chemotherapy and mitotane after microscopically incomplete tumour resection with spillage. Genomic analysis (gene panel sequencing and copy-number microarray) demonstrated a novel p.Phe338Leu tetramerisation domain (TD) variant in the proband and his cancer-free mother and a monoallelic deletion encompassing the locus in cancer tissue, consistent with cancer-predisposition syndrome. While the recurrent p.Arg337His variant translates into high ACC risk, residue 338 and, in general, TD domain variants drive heterogeneous clinical scenarios, despite generally being considered less disruptive than TP53 DNA-binding domain mutations.