Abstract
RATIONALE: Pilocytic astrocytoma (PA) typically shows biphasic pattern with a mixture of loose microcystic and compact regions, in which it is not uncommon to see heterogeneous morphology. However, there has not been reported in the literatures of the PA type that shows similarity to dysembryoplastic neuroepithelial tumor (DNT) in both histological morphology and immunophenotype. PATIENT CONCERNS: The present study described a case of PA affecting the right temporal-occipital lobe in a 22-year-old male patient. Morphologically, it composed of totally distinctive microcystic pattern. The classical biphasic pattern of PA was not observed. Immunohistochemically, neuronal marker NeuN was expressed in tumor cells scattered in the background which simulated its expression morphology in DNT. However, KIAA1549-BRAF fusion gene was identified by fluorescence in situ hybridization (FISH), supporting for the diagnosis of PA. DIAGNOSES: DNT-like PA (WHO grade I). INTERVENTIONS: The tumor was totally removed via a right temporal-occipital craniotomy. OUTCOMES: The patient is free of local recurrence and dissemination eleven months after surgical resection of the lesion. LESSONS: We herein report a rare case of DNT-like PA. For diagnosis, KIAA1549-BRAF fusion gene should be detected under similar situation.