DESMOPLASTIC INFANTILE GANGLIOGLIOMA (DIG)
Desmoplastic infantile gangliogliomas are rare neoplasms, that have been considered distinct clinicopathologic entities. Typically the lesions occur equally in male and female within the first two years of life accompanied by complex partial seizures (1). Computed tomography and magnetic resonance imaging typically reveal largely cystic tumors with a solid cortical component in the frontal and parietal lobes, which enhances intensely, and with moderate surrounding edema (1, 2). All reported cases are supratentorial, usually superficially situated with frequent extension to subarachnoid space and involvement of multiple lobes in more than half the cases. As in the present case, these tumors are characteristically firm due to extensive desmoplasia. Histologically tumor is composed of a mixture of spindle or enlarged astrocytes and occasional neuronal cells in a densely fibrous stroma. Immunohistochemistry demonstrates extensive glial differentiation but also neuronal epitopes in tumor cells with ambiguous features. Cells often binucleate that morphologically ganglion cells are also present. The cellular pleomorphism and atypia are frequently observed in this tumor and a diagnosis of a high-grade neoplasm should be avoided. Despite the cellular pleomorphism, atypia and mitosis, the prognosis has been considered favorable (3, 4). The treatment of choice for DIG is surgical resection and prolonged survivals of 14.5 years have been reported (4). If total surgical resection can be achieved, further therapy may not be indicated. In those patients with residual tumor, chemotherapy appears to be an effective form of therapy. The value of radiotherapy is not established (4, 5).
In contrast to the previous reports (1-5), the tumor in this case involved the brainstem extensively invaginating the mesocephalon precluding total resection. Although DIGs are thought to be indolent tumors, subsequent follow up demonstrated continued growth of residual tumor encouraging re-operation. Tumor progression determined by image studies occurred as early as 2 months after combined surgical resection and chemotherapy. These findings suggest that some DIGs, despite their histology, may behave more like WHO grade II lesions.
Acknowledgments The contributors would like to thank Dr. Peter Burger at Johns Hopkins University Medical Center for reviewing this case.
Contributed by Xuemo Fan, MD, PhD, Ted C Larson, MD, Mark T Jennings, MD, Noel B Tulipan MD, Steven A Toms, MD and Mahlon D Johnson, MD, PhD