Pilocytic Astrocytoma With Histological Malignant Features Without Previous Radiation Therapy -Case Report-

Abstract

Pilocytic astrocytoma sometimes transforms to a malignant type, and previous radiation therapy is considered to be a key factor. We report a case of pilocytic astrocytoma with histological malignant features without previous radiation therapy. A 21-year-old man presented a sudden onset of severe headache. Neuroimaging had detected a cystic mass in the posterior fossa at the age of one year without therapeutic intervention. On admission, computed tomography depicted a brain tumor in the posterior fossa with cystic components, intratumoral hemorrhage, and upward herniation. Urgent surgery was performed, and histological examination revealed some features of pilocytic astrocytoma but also broad necrosis, high cellularity, and MIB-1 labeling index of more than 20%. The histological diagnosis was pilocytic astrocytoma with malignant features. This tumor had continued a benign clinical course for 20 years, but had eventually transformed to a malignant type. Therefore, pilocytic astrocytoma may undergo spontaneous malignant transformation during its natural clinical course.

Heterogeneity of histopathological presentation of pilocytic astrocytoma – diagnostic pitfalls. A review

“…Only occasionally, tumours with brisk mitotic activity, necrosis and marked nuclear pleomorphism have been diagnosed as anaplastic PA [82]. It has been documented that anaplastic/malignant transformation of PA occurred most often in association with previous ionizing radiation [75] or surgery alone [88], whereas spontaneous malignant transformation was unique [10,72,90]. The majority of anaplastic cases have been described in adults [10,101].…”

“…The pilomyxoid variant of pilocytic astrocytoma (PMA) is suggested to represent a subtype with more invasive growth and increased risk of recurrences [49,50]. Occasionally, the classic PA may exhibit the distinct histological features of anaplasia such as necrosis, mitoses and vascular proliferation [10,25,31,53,82,90,101]. Some other factors, including partial resection, brainstem location and adult age, are also associated with a worse prognosis [27].…”

Primary Pilocytic Astrocytoma with Malign Transformation

“…Therefore, it is suggested that the primary tumor in the case can be PA and it can show malignant transformation spontaneously in the past 20 years with no treatment. Malignant transformation is suggested to be developed during the natural clinical course of tumor [10]. In our case, the lack of RT history shows that unexplained factors play a role in malignant transformation and the underlying mechanisms should be clarified.…”

Pilomyxoid astrocytoma showing malignant transformation in adult male

“…In a publication, histologically increased cellularity, cellular atypia and extensive necrosis in PA was defined as malignant transformation (19). According to some publications, malignant transformation is mostly seen after RT treatment and radiation is a key factor in malignant transformation (8).…”