Melanoma in children and adolescents: analysis of susceptibility genes in 123 Italian patients

UV-radiation and MC1R germline mutations are risk factors for the development of conventional and spitzoid melanomas in children and adolescents

BACKGROUND

Genomic characterisation has led to an improved understanding of adult melanoma. However, the aetiology of melanoma in children is still unclear and identifying the correct diagnosis and therapeutic strategies remains challenging.

METHODS

Exome sequencing of matched tumour-normal pairs from 26 paediatric patients was performed to study the mutational spectrum of melanomas. The cohort was grouped into different categories: spitzoid melanoma (SM), conventional melanoma (CM), and other melanomas (OT).

FINDINGS

In all patients with CM (n = 10) germline variants associated with melanoma were found in low to moderate melanoma risk genes: in 8 patients MC1R variants, in 2 patients variants in MITF, PTEN and BRCA2. Somatic BRAF mutations were detected in 60% of CMs, homozygous deletions of CDKN2A in 20%, TERTp mutations in 30%. In the SM group (n = 12), 5 patients carried at least one MC1R variant; somatic BRAF mutations were detected in 8.3%, fusions in 25% of the cases. No SM showed a homozygous CDKN2A deletion nor a TERTp mutation. In 81.8% of the CM/SM cases the UV damage signatures SBS7 and/or DBS1 were detected. The patient with melanoma arising in giant congenital nevus (CNM) demonstrated the characteristic NRAS Q61K mutation.

INTERPRETATION

UV-radiation and MC1R germline variants are risk factors in the development of conventional and spitzoid paediatric melanomas. Paediatric CMs share genomic similarities with adult CMs while the SMs differ genetically from the CM group. Consistent genetic characterization of all paediatric melanomas will potentially lead to better subtype differentiation, treatment, and prevention in the future.

FUNDING

Found in Acknowledgement.

Tumor predisposition: what's the skin got to do with it?

PURPOSE OF REVIEW

Recognition of skin findings associated with tumor predisposition syndromes can prompt early evaluation and surveillance and improve management. Additionally, knowing when to test and when to defer performing genetic testing can streamline management. This article reviews tumor predisposition syndromes with recently characterized skin findings and disorders for which early recognition and counseling can impact the course of disease.

RECENT FINDINGS

Café au lait macules (CALMs) are important in many tumor predisposition syndromes, and 'atypical' CALMs are associated with constitutional mismatch repair deficiency and Fanconi anemia. Melanoma predisposition syndromes caused by pathogenic variants in POT1 and BAP1 are more recently described, and both are associated with Spitzoid tumors. Somatic pathogenic variants can cause segmental nevoid basal cell carcinoma syndrome and a mosaic form of Peutz-Jeghers syndrome. Patients with PTEN hamartoma syndrome have increased risk for melanoma but this might not occur until adulthood.

SUMMARY

The cutaneous manifestations of tumor predisposition syndromes can aid diagnosis. Early photoprotection is key to modifying a main risk factor for skin cancer in many of these syndromes. Implementing surveillance guidelines facilitates early detection of tumors.