**Question:** All are true regarding Primary CNS lymphoma except

A. Lymphoma involving the central nervous system (CNS) is rare.
B. Symptoms are usually nonspecific and mimic other neurological disorders.
C. The diagnosis is straightforward using a single cerebrospinal fluid (CSF) examination.
D. Treatment involves only systemic chemotherapy.

**Correct Answer:** **D. Treatment involves only systemic chemotherapy.**

**Core Concept:** Primary CNS lymphoma (PCNSL) is a rare subtype of non-Hodgkin's lymphoma that affects the central nervous system (CNS). It typically occurs in immunocompromised individuals, such as those with AIDS, organ transplant recipients, or those receiving long-term corticosteroid therapy.

**Why the Correct Answer is Right:** In the majority of cases, treatment for PCNSL involves a combination of chemotherapy, including drugs like methotrexate, cytarabine, and dexamethasone. These drugs penetrate the blood-brain barrier and effectively target the malignant cells within the CNS. In some instances, local therapies like stereotactic radiotherapy (SRT) may be employed, especially for those patients where systemic chemotherapy is limited or contraindicated.

**Why Each Wrong Option is Incorrect:**

A. While PCNSL is not common, treatment strategies involve a combination of systemic chemotherapy, as mentioned above, not solely systemic chemotherapy.

B. PCNSL patients can present with a diverse array of symptoms and signs that can mimic various neurological disorders. The diagnosis is not straightforward and requires a combination of clinical, radiological, and laboratory assessments.

C. A single cerebrospinal fluid (CSF) examination may not be sufficient to diagnose PCNSL. Diagnosis typically involves a combination of clinical presentation, radiological imaging, and laboratory tests (e.g., CSF analysis, MRI, and PET-CT scans).

**Clinical Pearl:** PCNSL diagnosis often requires a multidisciplinary approach involving neurologists, oncologists, and neuro-imaging experts. Treatment approaches should be tailored according to the patient's overall health status, extent of CNS involvement, and presence of systemic lymphoma. Surgical interventions, such as biopsy, are often necessary to confirm the diagnosis and guide treatment selection.