IMG-12. Transient atypical brain and spine MRI features after high-dose chemotherapy may represent clumps of CD34+ hematopoietic stem cells

Abstract

Abstract High-dose chemotherapy is a therapeutic option in selected cases of pediatric high-grade brain tumor (pHGBT). Following high-dose chemotherapy, bone marrow is reconstituted by means of CD34+ peripheral blood stem cell (PBSC) infusion. Intravenously injected PBSCs have been reported to migrate to the Central Nervous System (CNS) and to persist for weeks. We report two cases of pHGBT in which, following PBSC infusion, we observed peculiar brain MRI signal alterations suggestive of clumps of CD34+ cells. A 15-month-old female underwent surgery and chemotherapy for an infratentorial, non-disseminated, Atypical Teratoid Rhabdoid Tumor. Following the second course of high-dose chemotherapy, MRI excluded residual disease, but revealed two contrast-enhancing nodules in the supratentorial ventricular system, with no evidence of diffusion restriction, unlike the primary tumor. Cerebrospinal fluid was collected by means of lumbar puncture and centrifuged: no neoplastic cells were found, while a few cells were positive when immunostained with anti-CD34 antibody. As no disease progression was documented, the patient completed her treatment with focal radiotherapy. Three months after the end of therapy, MRI showed new enhancing nodules with restricted diffusion, in keeping with leptomeningeal spread of disease; these progressively increased in size, despite subsequent lines of treatment, while the above-mentioned ventricular nodules shrank. Similar transient alterations were detected in a 4-year-old boy who had received treatment for high-risk Medulloblastoma, including high-dose chemotherapy. CONCLUSIONS: In the setting of new enhancing brain and spine findings with atypical MRI features, after high-dose chemotherapy to treat pHGBT, the hypothesis of CNS homing of CD34+ hematopoietic stem cells should be considered in the differential diagnosis.