Histological and genetic analysis of anaplastic pleomorphic xanthoastrocytoma suspected of malignant progression over a 12‐year clinical course

We report a case of anaplastic PXA for which histological study and molecular analysis were performed at the time of the first resection and two recurrences. A 15-year-old girl had a temporal lobe tumor that had been followed as a cystic lesion from three years of age without histopathological examination. The first and second surgical specimens exhibited typical histological features of PXA such as nuclear and cytoplasmic pleomorphism. In addition, microvascular proliferation was observed in the second surgical specimen. On the other hand, nuclear pleomorphism was unclear in the third surgical specimen and it was mainly composed of spindle cells. Palisading necrosis was observed. Mitotic figures and the Ki-67 proliferation index gradually increased. BRAF V600E and TERT promoter mutation were detected in the first, second, and third surgical specimens. In addition, PTEN mutation and CDNK2A deletion were detected in the third surgical specimen. Considering the histopathological and genetic changes over time, we concluded that our case of anaplastic PXA underwent malignant progression.