Intradural parenchymal involvement in the spinal subarachnoid space associated with primary lung cancer

Intradural parenchymal involvement (IPI) in the spinal subarachnoid space associated with primary lung cancer is rare. A retrospective study was undertaken to investigate the clinical and pathologic features of IPI.A total of 1215 cases of primary lung cancer were studied at autopsy; the results were reviewed retrospectively.Twenty (1.65%) of the cases revealed IPI in the spinal subarachnoid space. The histologic diagnoses were small cell carcinoma in ten cases, adenocarcinoma in eight cases, and squamous cell carcinoma in two cases. In 14 (70%) cases, the IPI was located between the lumbar and cauda equina of the spinal cord. However, no metastases were observed in the cervical spinal cord. Brain metastasis, vertebral metastasis, and meningeal carcinomatosis were seen in 70%, 60%, and 40% of the 20 cases, respectively, suggesting that these metastases may be related to the metastatic pathway to the spinal cord. Most patients had neurologic symptoms or signs referable to IPI; IPI could be diagnosed before death in only one patient by magnetic resonance imaging. The median interval between diagnosis of lung cancer and development of IPI and median survival after the onset of neurologic symptoms referable to IPI were 415 days and 110 days, respectively.The authors retrospectively received 1215 autopsies of patients with primary lung cancer and found 20 (1.65%) with IPI.