Adult recurrent pilocytic astrocytoma: Clinical, histopathological and molecular study

Background: PA is a grade I glial tumor that mostly occurs in children. However, although apparently similar to paediatric PA, adult PA presents a different clinical follow-up that could arise from specific molecular alterations. A variety of genetic alterations have been identified as diagnostic or prognostic glioma molecular markers.

Material and methods: We describe a right infratentorial tumor that occurred in a 58-year-old man. Neuroimaging and neuropathological examination suggested PA as an initial diagnosis. The tumor was completely resected. Unexpectedly, two years later, a rapidly growing tumor on the operative site was observed with a second location in the pineal region. Immunohistochemical reactions (IHC), Multiplex ligation probe amplification (MLPA) and fluorescence in situ hybridization (FISH) was performed in both primary and relapse tumor.

Results: Neuroimaging and neuropathological examinations suggested an unusual diagnosis for adult patients: a recurrent PA. Both MLPA and FISH analysis contribute to diagnostic confirmation by KIAA1549: BRAF fusion detection. Additional genetic results revealed interesting findings that justified the tumor aggressivity.

Conclusion: Molecular analysis of adult PA cases should be routinely combined with histopathological and neuroimaging examination to further refine prognostic diagnoses.