2025 Poster Presentations
P159: DIFFERENTIATING MENINGIOMA FROM PRIMARY BRAIN MELANOMA: A CASE REPORT OF A DIAGNOSTIC CHALLENGE IN STAGE IV NSCLC
Maxwell A Marino, DO, MPH1; Ali O Jamshidi, MD2; Fernando A Torres, MD3; 1Riverside University Health System, Moreno Valley; 2Kaiser Permanente Medical Center, Woodland Hills; 3Kaiser Permanente Medical Center, Los Angeles
This case report presents a 74-year-old male with Stage IV non-small cell lung carcinoma (NSCLC) and a diagnostic and management challenge concerning intracranial masses initially presumed to be meningiomas based on imaging studies. Post-surgical pathology unexpectedly revealed primary brain melanoma, highlighting the difficulty in distinguishing between these two entities based solely on imaging characteristics. This case offers an opportunity to explore potential neuroradiologic features that could aid in differentiating malignant melanoma from benign meningiomas, particularly in patients with a known history of malignancy.
The patient had a history of NSCLC with metastatic involvement, including spinal metastasis, and underwent MRI and PET-CT for brain lesion evaluation. The patient was found to harbor multiple presumed small metastases that were treated with stereotactic radiosurgery. The imaging also revealed two right-sided extra-axial masses, measuring 4.3 cm and 2.0 cm, respectively. Both masses were initially considered likely to be meningiomas due to their location and imaging characteristics, including photopenia on PET-CT and lobulated margins on MRI. The patient subsequently underwent a right pterional craniotomy and resection of the lesions, which revealed extra-axial masses consistent with malignant tissue. Postoperative pathology identified these lesions as primary brain melanoma, confirmed by immunohistochemical staining positive for SOX10 and HMB45.
This case underscores the limitations of imaging in differentiating meningioma from melanoma in patients with concurrent malignancies. Meningiomas are typically slow-growing, benign tumors, whereas melanoma, particularly metastatic or primary brain melanoma, can exhibit aggressive growth and mimic benign lesions on imaging. In this case, the masses had atypical imaging features, such as heterogeneous postcontrast enhancement, which, while suggestive of meningioma, should raise suspicion for malignancy in the context of a known cancer history. Key imaging distinctions, including increased vascularity and atypical enhancement patterns, may provide neuroradiologists with better diagnostic clues in similar cases.
This case highlights the importance of maintaining a broad differential diagnosis in patients with known malignancies, even when imaging findings suggest benign processes like meningioma. This awareness is critical as once the diagnosis was made, the patient’s oncologist wanted to ensure that the patient had a GTR, which was achieved as he had a Simpson grade 1 resection. Future work may focus on refining neuroradiological criteria for distinguishing between benign and malignant extra-axial masses, particularly in patients with known systemic malignancies.