Primary leptomeningeal CD30 positive diffuse large B cell lymphoma disguise as meningioma in a young adult: a case report.

Primary leptomeningeal lymphoma (PLML) without brain parenchymal involvement or systemic disease is very rare, comprising of approximately 7% of all primary central nervous system lymphomas (PCNSL). PLML is a diagnosis of exclusion which should be confirmed on biopsy after ruling out metastasis from systemic lymphomas and dissemination from PCNSL. A 21-year-old patient presented with the chief complaints of headache, diplopia, decreased vision for five months, and a swelling on the left side of the forehead for four months. On radiology, a large, lobulated, extra-axial mass lesion along the left frontal region with its base towards dura noted. No parenchymal or subependymal CNS lesions were found on CT/MRI. Histopathology was reported as primary leptomeningeal CD30 positive diffuse large B cell lymphoma. PLML is a very rare meningeal tumor that requires a very high index of suspicion and is always a diagnosis of exclusion.