SYNCHRONOUS T-LYMPHOBLASTIC LYMPHOMA AND NEUROBLASTOMA IN A 3-YEAR-OLD WITH NOVEL GERMLINE SMARCA4 AND EZH2 VARIANTS.

T-lymphoblastic lymphoma is the most common lymphoblastic lymphoma in children, and often presents with a mediastinal mass. Lymphomatous suprarenal masses are possible but rare. Here we discuss the case of a previously healthy 3-year-old male who presented with mediastinal T-lymphoblastic lymphoma (T-LLy) with bilateral suprarenal masses. Following initial treatment, surgical biopsy of persisting adrenal masses revealed bilateral neuroblastoma (NBL). A clinical genetics panel for germline cancer predisposition did not identify any pathogenic variants. Combination large panel (864 genes) profiling analysis in the context of a precision oncology study revealed two novel likely pathogenic heterozygous variants: SMARCA4, c.1420-1G>T, p.? and EZH2 c.1943G>C p.(Ile631Phefs*44). Somatic analysis revealed potential second hits/somatic variants in EZH2 (in the T-LLy) and a segmental loss in chromosome 19p encompassing SMARCA4 (in the NBL). Synchronous cancers, especially at a young age warrant genetic evaluation for cancer predisposition; enrollment in a precision oncology program assessing germline and tumour DNA can fulfill that purpose, particularly when standard first line genetic testing is negative and in the setting of tumors that are not classic for common cancer predisposition syndromes.