Brain Pathology Case of the Month - May 2019

FINAL DIAGNOSIS

Drop metastasis of an anaplastic oligodendroglioma

DISCUSSION

Malignant progression in patients with oligodendroglioma is inevitable [3]. However, the prognosis is generally more favorable than astrocytomas of the corresponding grade. Oligodendrogliomas, which usually arise in the cerebral hemispheres, primarily recur locally, typically within the resection margins or treatment fields [2]. Nevertheless, spinal drop metastasis from oligodendroglioma is a rare finding with fewer than a dozen cases since first reported in 1971 [1]. In the present case, 14-years elapsed after the initial diagnosis of oligodendroglioma. During a staging MRI for metastatic adenocarcinoma, an intradural tumor attached to the conus medullaris was detected, which was considered compatible with schwannoma or ependymoma. Surprisingly, histopathological examination revealed an anaplastic oligodendroglioma. Of note, additional tumor resection of the intracranial oligodendroglioma was performed 4 months after resection of the spinal drop metastasis. Histological examination revealed features of anaplastic oligodendroglioma with co-deletion of 1p/19q.

While primary brain tumors such as glioblastoma, followed by primitive neuroectodermal tumors (PNET) and ependymomas are more likely to metastasize to the spinal canal, metastatic spread of oligodendroglioma is exceedingly rare [1]. The mechanism underlying the metastatic spread of oligodendroglioma is controversial, with possible pathways including tumor dissemination via the cerebrospinal fluid pathways or even hematogenous spread. In cases of leptomeningeal disease or scalp involvement associated with multiple craniotomies, spread along lymphatic channels to regional lymph nodes followed by distal metastases is discussed [2]. Tumor dissemination via the cerebrospinal fluid, reported in up to 14% of patients with oligodendroglioma, is thought to arise after surgical intervention with breaching the pia mater and ependymal lining [4]. Isolated intramedullary metastases are suggested to occur from hematogenous dissemination.

The short survival in patients with anaplastic oligodendroglioma combined with the relatively slow growth rate has been considered as an explanation for the rare occurrence of metastasis [1]. Thus, in future, the incidence of patients with spinal drop metastasis of oligodendroglioma is likely to increase due to improved therapies and longer survival of patients

REFERENCES

1. Carlsen JG, Tietze A, Lassen YA & Rosendal F (2012) Paraplegia due to drop metastases from anaplastic oligodendroglioma. Br J Neurosurg 26:94-95.
2. Costigan DA & Winkelman MD (1985) Intramedullary spinal cord metastasis. A clinicopathological study of 13 cases. J Neurosurg 62:227-233
3. Jaeckle KA, Decker PA, Ballman KV, Flynn PJ, Giannini C, Scheithauer BW et al (2011) Transformation of low grade glioma and correlation with outcome: An NCCTG database analysis. J Neurooncol 104:253-259.
4. Macdonald DR, Brien RA, Gilbert JJ & Cairncross JG (1989) Metastatic anaplastic oligodendroglioma. Neurology 39:1593 - 1596.

Contributed by Julia Velz, David Bellut, Niklaus Krayenbühl, Sebastian Winklhofer, Elisabeth Rushing, Katrin Frauenknecht

International Society of Neuropathology