{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T02:25:45Z","timestamp":1777861545503,"version":"3.51.4"},"reference-count":15,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T00:00:00Z","timestamp":1777507200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Primary diffuse leptomeningeal melanocytosis (PDLM) is a rare central nervous system neoplasm. Diagnosis is challenging in amelanotic variants because they lack the characteristic T1 hyperintensity on magnetic resonance imaging (MRI), leading to confusion with infectious meningitis or hemorrhage.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case Presentation<\/jats:title>\n                    <jats:p>A 24-year-old male presented with severe headache and neck stiffness. Initial computed tomography suggested a subarachnoid hemorrhage (SAH); however, digital subtraction angiography was negative. MRI revealed diffuse leptomeningeal enhancement without T1 hyperintensity. Cerebrospinal fluid (CSF) analysis was non-diagnostic. Owing to progressive clinical deterioration despite CSF diversion, a biopsy was performed. Histopathology confirmed amelanotic PDLM with positive S-100, HMB-45, and Melan-A markers, but negative Fontana-Masson staining. Hematology-oncology consultation recommended MEK inhibitor therapy based on MAPK pathway rationale; however, molecular genetic profiling was pending and the patient\u2019s rapid neurological deterioration precluded initiation of targeted therapy. The patient succumbed to the disease approximately 3 months after biopsy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>This case highlights the diagnostic pitfalls of amelanotic leptomeningeal melanocytosis and the narrow therapeutic window in advanced PDLM. In young patients with \u201cangiogram-negative SAH\u201d or unexplained leptomeningeal enhancement, the absence of T1 hyperintensity should not exclude melanocytic neoplasms. Early biopsy and prompt molecular profiling are crucial for timely diagnosis and treatment planning.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fonc.2026.1768860","type":"journal-article","created":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T04:25:09Z","timestamp":1777523109000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Primary amelanotic leptomeningeal melanocytosis mimicking subarachnoid hemorrhage: a case report of the deceptive masquerader"],"prefix":"10.3389","volume":"16","author":[{"given":"Yu-Chung","family":"Juan","sequence":"first","affiliation":[{"name":"Department of Neurosurgery, China Medical University Hospital","place":["Taichung, Taiwan"]},{"name":"Neuroscience and Brain Disease Center, China Medical University","place":["Taichung, Taiwan"]},{"name":"Graduate Institute of Biomedical Sciences, China Medical University","place":["Taichung, Taiwan"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"John S.","family":"Kuo","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, China Medical University Hospital","place":["Taichung, Taiwan"]},{"name":"Neuroscience and Brain Disease Center, China Medical University","place":["Taichung, Taiwan"]},{"name":"Graduate Institute of Biomedical Sciences, China Medical University","place":["Taichung, Taiwan"]},{"name":"Department of Neurosurgery, Dell Medical School, The University of Texas at Austin","place":["Austin, TX, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chun-Chung","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, China Medical University Hospital","place":["Taichung, Taiwan"]},{"name":"Neuroscience and Brain Disease Center, China Medical University","place":["Taichung, Taiwan"]},{"name":"Graduate Institute of Acupuncture Science, China Medical University","place":["Taichung, Taiwan"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ren-Ching","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Pathology, China Medical University Hospital","place":["Taichung, Taiwan"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Der-Yang","family":"Cho","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, China Medical University Hospital","place":["Taichung, Taiwan"]},{"name":"Neuroscience and Brain Disease Center, China Medical University","place":["Taichung, Taiwan"]},{"name":"Graduate Institute of Biomedical Sciences, China Medical University","place":["Taichung, Taiwan"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yu-Kai","family":"Cheng","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, China Medical University Hospital","place":["Taichung, Taiwan"]},{"name":"China Medical University Children\u2019s 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