The characteristics of cerebrospinal fluid anaplastic large cells in a patient with primary leptomeningeal anaplastic large cell lymphoma

Primary central nervous system lymphomas (PCNSL) anaplastic large cell lymphoma (ALCL) are very rare non-Hodgkin’s lymphomas, especially in the leptomeninges. Until now, the diagnostics and therapeutics of PCNSL-ALCL is a challenge and urgent need. A 26-y Chinese male presented altered awareness and severe headache. A 26-y Chinese male presented altered awareness and severe headache. Brain magnetic resonance imaging (MRI) delineated no intracerebral lesions and focal leptomeningeal enhancement. Diagnosis was based on cerebrospinal fluid (CSF) examination discovering anaplastic large cells (ALCs) with positive expression for anaplastic lymphoma kinase (ALK) and CD30, and no evidence of systemic involvement. In addition, we firstly performed the single-cell RNA sequencing to identify transcriptome characteristics of CSF-ALCs. The case was diagnosed as a rare primary leptomeningeal anaplastic large cell lymphoma (PL-ALCL). Four cycles of systemic chemotherapy with methotrexate and intrathecal cytarabine help achieve complete remission. Compared to normal T cells, 45 genes were specifically upregulated in CSF-ALCs. CSF-ALCs enriched cell proliferation and metabolism pathway and lost features of immune identity. The heterogeneity of CSF-ALCs were manifested in the expression of cancer-testis antigens and cell-cycle signature genes. In addition, the gene regulatory networks (GRNs) revealed the activity of transcription factors EZH2 and NFYC were upregulated in the CSF-ALCs. The first analysis of single-cell transcriptome signatures of CSF-ALCs will provide clues for diagnosis and mechanism research of PL-ALCL.