American Board of Internal Medicine (ABIM) Certification Practice Exam

What is necessary to confirm a diagnosis of primary central nervous system lymphoma before treatment?

1. Physical examination

2. Neuroimaging

3. Pathologic analysis of a brain biopsy

4. Patient history review

The correct answer is: Pathologic analysis of a brain biopsy

To confirm a diagnosis of primary central nervous system lymphoma (PCNSL) before initiating treatment, pathologic analysis of a brain biopsy is essential. PCNSL is a malignant brain tumor that primarily occurs in the context of immune suppression. While neuroimaging techniques, such as MRI or CT scans, can reveal lesions consistent with lymphoma, they cannot definitively diagnose the condition. These imaging studies can suggest the presence of a tumor but can also lead to misinterpretation, as various lesions may share similar imaging characteristics. The patient’s history and physical examination are important components of the overall clinical assessment, as they help to guide the diagnostic process and identify potential symptoms associated with PCNSL. However, neither of these elements provides the definitive confirmation of the disease. Pathologic analysis through a biopsy involves obtaining a tissue sample from the suspected lesion and examining it microscopically. This is crucial because it allows for the identification of the characteristic cellular features of lymphoma, such as atypical lymphoid cells and specific markers that confirm the diagnosis. Without this definitive pathologic confirmation, treatment might be misdirected, as other conditions could mimic PCNSL on imaging studies. Therefore, obtaining a tissue sample for biopsy and performing pathologic analysis is the gold standard for