Primary dural lymphoma: a novel concept of heterogeneous disease.

Spinal primary dural lymphoma (PDL) is uncommon with a total of 37 previous well-documented cases reported, including one diagnosed in the authors' institution. More recently we encountered an additional case of spinal PDL that, similarly to our previous case, was grade 1-2 follicular B-cell PDL. Our two cases were diagnosed over a 3-year interval in a 72-year-old female and a 74-year-old male, respectively. An exhaustive literature review on PDL was performed consequently to reveal that: (i) spinal and cerebral sites of involvement by PDL are constantly mutually exclusive; and (ii) unlike cerebral PDL, which is usually of marginal zone B-cell type, only two of the 38 cases of spinal PDL were diagnosed as such, diffuse large B-cell lymphoma being the most commonly encountered type in the spine. This divergence infers that, in contrast to the prevailing concept that PDL is a unique disease group, PDL appears to be rather heterogeneous with a difference in predilection of lymphoma type for the anatomical site of dural involvement. Such a site-specific lymphoma-type predilection phenomenon, well-recognized in other organ systems, has not been acknowledged in PDL. This report brings new insights into PDL, and may contribute to a better understanding of nervous system pathophysiology and lymphoma classification.