[Primary CNS lymphomas. Morphology and diagnosis]

Area of Science:

• Neuropathology
• Oncology
• Immunohistochemistry

Context:

• Primary central nervous system lymphomas (PCNSL) present diagnostic challenges, often requiring differentiation from glioblastoma and brain metastases.
• Histological analysis reveals that most PCNSL cases are diffuse large B-cell lymphomas, with BCL6 expression observed in 80%.

Purpose:

• To outline the diagnostic criteria and histological features of primary central nervous system lymphomas (PCNSL).
• To differentiate PCNSL from other brain tumors like glioblastoma and metastases.
• To describe various PCNSL subtypes and their characteristic cellular morphology.

Summary:

• Stereotactic biopsy with intraoperative smear cytology is the preferred diagnostic method for PCNSL, detecting lymphoid blasts.
• Immunohistochemistry, utilizing markers such as CD20 and CD79a, is crucial for confirming B-cell lineage.
• Key differentiating features from high-grade gliomas include the absence of endothelial proliferations in PCNSL.
• PCNSL variants include anaplastic, T-cell rich, and intravascular types. HIV/AIDS-associated PCNSL shows plasmoblastic or Burkitt-like cells and necrosis. Primary leptomeningeal lymphomas are rare and diagnosed via cerebrospinal fluid cytology.

Impact:

• Accurate differentiation of PCNSL is critical for appropriate patient management and treatment planning.
• Understanding PCNSL heterogeneity aids in precise diagnosis and subtyping.
• This information supports neuropathologists and oncologists in diagnosing complex CNS malignancies.