Rare case of leptomeningeal small lymphocytic lymphoma with TP53 mutation detected by deep next-generation sequencing.

Involvement of the central nervous system (CNS) is an exceedingly rare presentation of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), with no consensus on the optimal therapy. Here we describe a 71-year-old man with a skull-base leptomeningeal mass consistent with SLL on biopsy. Malignant cells were observed in the cerebrospinal fluid (CSF), but not in the peripheral blood, bone marrow, or other extramedullary sites. Molecular analysis of the patient's disease by next generation sequencing (NGS) detected no pathogenic mutations in 111 genes, with the exception of two low allele frequency variants identified during deep NGS analysis of TP53. The patient was treated with six cycles of high-dose methotrexate and systemic/intrathecal rituximab followed by venetoclax monotherapy, with complete resolution of CSF disease and radiographic decrease in size of the skull base lesion.