Deckert and colleagues investigated PCNSL for the presence of lymphatic vessels using immunohistochemistry for Lyve-1, podoplanin, and Prox-1 expression in a series of 20 intraparenchymal PCNSL biopsies in comparison with 8 dural/meningeal-based foci of systemic diffuse large B-cell lymphoma (DLBCL) as well as 20 glioblastomas lacking any contact with the meninges.
|Absence of lymphatic vessels in PCNSL demonstrated by|
negative Prox-1 staining
(inset: human tonsils serve as positive control)
tumors) in areas where the tumors had invaded the fibrous tissue of the dura. Taken together, the immunohistochemical panel demonstrated lymphatic vessels in 7 out of 8 (87.5%) of the DLBCLs investigated.
The authors note that although cerebrospinal fluid drains to lymph nodes through a variety of routes, these passages are presumably too small to allow passage of large neoplastic lymphocytes.
This report leaves one glaring question unanswered: If one investigated glioblastomas that did have contact with the dura/meninges, would those show evidence of lymphatic vessels? If so, why do those glioblastomas not metastatize to areas outside the CNS?