Neurosurgical staging of midline intra-axial (nuclear) tumors

A staging system is needed for midline intra-axial (nuclear) tumors so that treatment results can be compared, insights about tumor biology can be obtained, and prognosis can be estimated. The TNM staging classification is of limited value because nuclear tumor margins cannot be defined by an operation, there are no nodes to sample, and the tumors rarely metastasize. Nuclear tumors can be staged best now by computed tomography (CT) and pathology findings. Diagnostic staging by CT scans will demonstrate tumor features that may be of prognostic importance: tumor size, density, volume, enhancement, laterality, and presence of cysts and calcifications. In the current series, prognosis was better for tumors with cysts or calcifications, and for tumors less than 5 cm, but correlated poorly with laterality and site. Biopsy and often partial resection can be performed on nuclear tumors with low risks, but operative staging is not helpful because operations are necessarily limited. Most diencephalic tumors are astrocytomas or mixed gliomas, but approximately 15% are malignant astrocytomas or malignant mixed gliomas that need more intensive therapy, and 5% to 10% are neoplasms such as hamartomas that require no additional therapy. Two individual histopathologic characteristics, high cell density and mitoses, indicate a worse prognosis. Pediatric brain tumor study groups need to accumulate additional radiographic and pathologic information to stage nuclear tumors more accurately.