Hematogenous metastases of carcinoma to dorsal root ganglia.

Hematogenous metastases of carcinoma to dorsal root ganglia was found in 2 of approximately 500 consecutive autopsies in which a lumbar dorsal root ganglion was routinely examined microscopically. The primary tumors were poorly differentiated colonic adenocarcinoma and oat cell carcinoma of the lung, both with widespread hematogenous metastases which spared the central nervous system. No symptoms were detected clinically. In the same series of patients the sural nerve as well as the lumbar plexus were histologically sampled but no examples of distant endoneurial metastases were found. The vascular endothelium of dorsal root ganglia is fenestrated and, presumably as a consequence, provides no blood-ganglion barrier. This microvascular difference may account for the susceptibility of the ganglia to metastases when compared to nerve trunks which posses unfenestrated endothelium and blood-nerve barrier.