Pediatric Primary Diffuse Leptomeningeal Primitive Neuroectodermal Tumor: A Case Report and Literature Review

Background: Primary diffuse leptomeningeal primitive neuroectodermal tumor (PDL PNET) is extremely rare, with only 19 cases reported in the literature to date. We present a case of a child with rapidly progressive PDL PNET and a literature review. A 10-year-old boy presented with mood lability, hallucinations, generalized pain, enuresis, and headaches. Initial investigation failed to produce a diagnosis. The symptoms progressed to seizure, back pain, and papilledema. Imaging showed acute hydrocephalus and mild diffuse leptomeningeal enhancement without an identifiable primary lesion. Methods: The hydrocephalus was managed with a ventriculostomy - later replaced by a ventriculoperitoneal shunt after ruling out infection. A dura mater biopsy obtained prior to shunt insertion was unrevealing. Repeat MRI at the 2-month follow-up showed severe interval progression of the leptomeningeal enhancement with thick lumbar spinal subdural enhancing areas. A biopsy from the inflamed arachnoid at the L3-L4 level unveiled a leptomeningeal PNET diagnosis. Results: Despite adjuvant therapy with chemoradiation, the disease progressed, and the patient died 22 months after the initial presentation. Nineteen other cases of PDL PNET have been reported in the literature and were analyzed. Conclusion: Primary leptomeningeal PNET is an extremely rare disease. Optimal treatment is not well established, and the prognosis is very poor.