Path-17. pilocytic astrocytoma exhibiting diffuse leptomeningeal dissemination: extremely rare form of low-grade glioma with dichotomous (children versus adults) and uncharacteristically aggressive behavior

Abstract OBJECTIVE To identify all prior reports of pilocytic astrocytoma (PA) exhibiting diffuse leptomeningeal dissemination (LMD) (WHO Grade I) in an effort to comprehensively characterize this anomalous, predominantly pediatric pathology. METHODS A systematic review of the literature was performed using the PubMed, Scopus, and Web of Science databases. RESULTS Twenty-nine studies featuring 60 patients (54 pediatric,6 adult) were identified.The mean age at initial diagnosis was 10.2 ± 10.6 years (range, 0.3 to 55 years), and most of the patients were male (n=39,65.0%). The most common primary tumor locations were the hypothalamus (n=18,30.0%), cerebellum (n=16,26.7%), and optic chiasm (n=8,13.3%). Signs/symptoms at presentation included paralysis, cerebellar findings, and symptomatic, obstructive hydrocephalus. Most patients underwent surgery alone (n=26,43.4%) or in combination with radiotherapy (n=10,16.7%) or chemotherapy (n=8,13.3%). Of 43 patients who underwent surgery, subtotal resection (STR) was achieved in 26. STR appeared to be a risk factor for future LMD and poor prognosis. Additionally, adjuvant therapy did not seem to reduce the odds of subsequent LMD. Twenty-two patients (36.7%) were found to have LMD at presentation. Time to dissemination for the remaining patients ranged from between 3.6 - 206 months. Among all the included patients, 24 (40%) exhibited LMD within the brain only, 22 (36.7%) within the spine only, and 14 (23.3%) within both locations. Multi-agent chemotherapy alone (n=20, 33.3%) was the most commonly utilized treatment modality, followed by radiotherapy alone (n=13,21.7%), surgery with radiotherapy (n=10,16.7%), and surgery alone (n=5,8.3%). The mean follow-up duration was 44.2 ± 47.7 months (range, 0 to 221 months). Mortality occurred in 18 out of the 58 patients who had follow-up information available, with a mean time from LMD diagnosis to death of 19.9 ± 23.6 months. CONCLUSION Given its truly anomalous behavior, future concerted efforts to analyze the genetic profile of all identified tissue samples of PA with LMD is warranted.