June 2020 — Neuropathology

By MCL Education • June 9, 2020

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A 25-month-old female presented with eye deviation and ataxia and was found to have a large mass filling the fourth ventricle. The tumor was resected, and histopathological analysis showed a solid and papillary pattern of growth with poor differentiation, high mitotic activity, and areas of necrosis (Figure 1). The tumor also showed diffuse CAM5.2 immunostain, focal synaptophysin positivity, lacked expression of glial markers GFAP and Olig2, and showed loss of INI-1 and largely of H3 K27me3 expression. Overall, the tumor resembled a choroid plexus carcinoma. Tumor purity was morphologically estimated as 70%. Molecular and cytogenetic analyses were performed at the Mayo Clinic Genomics Laboratory. Neuro-oncology NGS testing showed a SMARCB1 mutation involving a canonical splice site in 84% of all sequencing reads (c.986+2T>G) (Figure 2). Chromosomal microarray identified losses along chromosomes 11 (including genes NUP98, IGF2, H19, and CDKN1C), 22 (including genes SMARCB1, MN1, NF2, EWSR1, and CHEK2), and X (Figure 3).

	Cinthya Jeanette Zepeda Mendoza, Ph.D. Fellow, Laboratory Genetics and Genomics Mayo Clinic
	Kandelaria (Ande) Rumilla, M.D. Consultant, Laboratory Genetics and Genomics Mayo Clinic Assistant Professor of Laboratory Medicine and Pathology Mayo Clinic College of Medicine and Science
	Caterina Giannini, M.D., Ph.D. Consultant, Anatomic Pathology Mayo Clinic Professor of Laboratory Medicine and Pathology Mayo Clinic College of Medicine and Science

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