A 29-year-old man presented in 1984 with a recent onset of partial seizures
marked by speech arrest. Electroencephalography identified a left frontote
mporal dysrhythmia. Computerized tomography (CT) scanning revealed a superf
icial hypodense nonenhancing lesion in the midleft frontal convexity, with
some remodeling of the overlying skull. The patient was transferred to the
London Health Sciences Centre for subtotal resection of what was diagnosed
as a "fibrillary astrocytoma (microcystic)." He received no chemotherapy or
radiation therapy and remained well fur 11 years.
The patient presented again in late 1995 with progressive seizure activity.
Both CT and magnetic resonance imaging demonstrated a recurrent enhancing
partly cystic lesion. A Grade IV astrocytoma was resected, and within the m
alignant tumor was a superficial area reminiscent of a dysembryoplastic neu
roepithelial tumor (DNT). Data on the lesion that had been resected in 1984
were reviewed, and in retrospect the lesion was identified as a DNT of the
complex form. It was bordered by cortical dysplasia and contained glial no
dules, in addition to the specific glioneuronal element. The glial nodules
were significant for moderate pleomorphism and rare mitotic figures. The Ki
67 labeling index averaged 0.3% in the glial nodules and up to 4% focally.
Cells were rarely Ki67 positive within the glioneuronal component. This cas
e is the first documented example of malignant transformation of a DNT. It
serves as a warning of the potential for malignant transformation in this e
ntity, which has been traditionally accepted as benign. This warning may be
especially warranted when confronted with complex forms of DNT. The comple
teness of resection in the benign state is of paramount importance.