ID #344 Giant intracranial melantoic neuroectodermal tumour of infancy: report of 2 cases

Background Melantoic neuroectodermal tumour of infancy (MNTI) is an extremely rare neoplasm with a predilection for the very young. These lesions are postulated to originate from neural crest cells and tend to be found within craniofacial bones. To date, there is a paucity of knowledge regarding its pathogenesis and optimal treatment regimen. We present 2 infant cases of intracranial MNTI and discuss their management nuances. Case description Patient 1 was a 5-month-old female who presented with an asymptomatic left frontal scalp swelling. Neuroimaging reported a 5.4 cm frontotemporal space-occupying lesion causing significant mass effect. Gross total resection was achieved. No adjuvant treatment was administered. Patient 2 was an 8-month-old male who presented with a painless left retro-auricular swelling. His scans showed a 5.5 cm temporal bony mass with invasion into the antero-lateral skull base. He underwent an initial tumour debulking, followed by 7 cycles of OJEC chemotherapy as per infant neuroblastoma protocol. A second resection was performed, and he completed 3 more cycles of chemotherapy. For both patients, the post-resection calvaria defects were reconstructed by the plastics surgery team. Result Histology for both patients revealed a biphasic tumour composed of neuroblasts set within neuropil admixed with pigmented epithelioid cells. The neuroblasts label for synaptophysin and NeuN, and the pigmented epithelioid cells label for AE1/3 and HMB45. The Ki67 index were <1%. Patient 2’s tumour was further interrogated by firstly, the AmpliSeqTM Childhood Cancer Panel sequencing that showed no pathogenic alterations; and next, DNA methylation profiling (DKFZ v12.8 brain classifier) which was non-classifiable. At 15 and 3 years’ follow-up respectively, the patients remain neurologically well with no radiological evidence of tumour recurrence. Conclusions Giant intracranial MNTI tumours pose therapeutic challenges to the paediatric neuro-oncology team. We advocate an individualised approach by an experienced multidisciplinary team to achieve favourable long-term outcomes.