Lymphoma, CNS

Central nervous system (CNS) lymphomas are defined by involvement of the brain, eyes, or spinal cord, and are categorized as primary (isolated to the CNS) or secondary (disseminated from systemic sites). They present with varied radiographic features on contrast-enhanced MRI (see below cases). These tumors are highly sensitive to chemo- and radiation therapy, and aggressive surgical resection is not considered the standard treatment. Thus, when CNS lymphoma is suspected, it is prudent to prioritize a minimally invasive stereotactic needle biopsy or a mini-craniotomy for definitive histopathology.^[1] Notably, corticosteroids should be withheld prior to tissue acquisition whenever possible to avoid the "vanishing tumor" phenomenon, which can lead to non-diagnostic results.^[2]

Cases

1

A senior patient presented with altered mental status. CT head without contrast in the emergency department showed a large hyperdense lesion (red arrow) at the left basal ganglia with surrounding hypodense edema (yellow arrow), causing compression of the left lateral ventricle and midline shift. Brain MRI with contrast demonstrated a similar heterogenously enhanced lesion. Differential diagnosis included CNS lymphoma, meningioma, and metastasis, etc. A left frontal stereotactic needle biopsy was performed and pathology showed a high-grade B-cell lymphoma.

2

A middle-aged patient presented with a one-week history of confusion. A CT scan of the head revealed a 3.5 cm left frontal lesion with associated perilesional edema and a 4 mm midline shift. Brain MRI with contrast demonstrated a left frontal, contrast-enhancing lesion (red arrow) displaying an open-ring sign (yellow arrow). Sagittal views also showed suspected Dawson's finger (cyan arrow) oriented perpendicular to the left lateral ventricle. The differential diagnosis included demyelinating disease (specifically tumefactive multiple sclerosis) and neoplastic processes. A left frontal stereotactic needle biopsy was performed, and histopathology confirmed high-grade diffuse large B-cell lymphoma (DLBCL). Post-operative CT head showed a small hemorrhage (green arrow) at the biopsy site. The patient subsequently underwent chemotherapy and recovered well. At the three-month clinical follow-up, the patient had a GCS of 15 and no neurological deficits.