Practical aspects regarding the histopathological grading and anaplastic transformation of gangliogliomas – a literature review

Ganglioglioma represents a benign central nervous tumor, occurring predominantly in the pediatric population and affecting the temporal lobe. It is also renowned for its epileptogenic potential. However, to date, there are numerous uncertain features about this tumor, especially about its grading system. In the former World Health Organization (WHO) Classification of central nervous tumors system, gangliogliomas could have been attributed one out of three grades: grade I (benign), grade II (atypical), and grade III (anaplastic). The new classification systems have renounced to atypical ganglioglioma nomenclature, due to the lack of histopathological criteria for this entity. Another controversial aspect of grade I ganglioglioma is its potential to transform into a malignant tumor, namely, most frequently an anaplastic ganglioglioma. Based on our knowledge, there are no literature reviews to date focusing on anaplastic transformation potential. The present paper encompasses all anaplastic transformation of gangliogliomas and has analyzed the time frame between the two events, the age of the patients and its relationship to the complete or subtotal resection and administration of radiotherapy. Thirty-three cases of malignant transformation of ganglioglioma have been reported so far in the literature, with 54.54% of them undergoing progression to anaplastic ganglioglioma and 21.21% to anaplastic ganglioglioma. Median age was 26 years, and the cases were evenly distributed between the two genres. Only 27.27% of all evaluated cases had been administrated adjuvant radiotherapy, and only 44% of the latter have had an incomplete tumoral resection.