Abstract
Lymphomas involving the central nervous system (CNS) have worse outcomes, including both primary and secondary CNS lymphomas, which are associated with poorer overall survival outcomes. The World Health Organization classifies CNS lymphoma as arising from the brain, leptomeninges, and spinal cord, but this simplified CNS anatomical definition fails to incorporate areas of ambiguity that can be clinically relevant for treatment decision making. In this article, we review the anatomical boundaries of CNS lymphoma within select border-zone biological structures located at the CNS borders in order to gain a consensus working definition of CNS disease boundaries. We review anatomical localizations with border-zone CNS boundaries, including the dura, cavernous sinus, circumventricular organs, pituitary gland, and cranial nerves. Though some portions of the eye would be considered CNS and others extra-CNS, recommendations for this structure are outside the scope of this review. Through this review, we examine the impact of lymphomatous invasion on select CNS-bordering anatomical structures, aiming to better define treatment categorization as CNS or extra-CNS, with a focus on B cell lymphoma types.