Integrated Genomic Characterization of a Pineal Parenchymal Tumor of Intermediate Differentiation

Abstract

Pineal parenchymal tumors of intermediate differentiation (PPTIDs) are rare lesions. The differential diagnosis and management strategy for PPTIDs can be challenging because of the variable prognostic and pathologic characteristics of these tumors. A 24-year-old man presented with progressive headaches, gait abnormalities, and abulia. Magnetic resonance imaging revealed a large T1-hypointense, T2-isointense, contrast-enhancing, partially cystic mass of the pineal and tectal region. Near-total resection was achieved in a 2-stage operation followed by focal and craniospinal irradiation and adjuvant chemotherapy. Immunohistochemical analysis including use of pineal lineage marker confirmed a diagnosis of PPTID. Targeted exome sequencing showed mutations in TSC1(L388P) and IKZF3(F206C), whereas high-resolution array cytogenetics revealed losses in chromosomes 2, 3, 4, 8, 10, 11, 17, and 20, leading to single-copy loss of PTEN and TP53. Pineal parenchymal tumors reflect a broad spectrum of malignancy potential and prognoses, which mandate better understanding of the disease mechanism for rational therapeutic strategies. We present a case of PPTID and report several mutations and chromosomal abnormalities previously unrecognized in this tumor subtype. Review of the literature highlights a need for surgical resection followed by adjuvant chemoradiation. Further investigation of these novel variants may improve understanding of the pathogenesis underlying pineal parenchymal tumors.