Pilomyxoid astrocytoma with high proliferation index

Abstract

Pilomyxoid astrocytomas is an uncommon aggressive piloid neoplasm, closely related to pilocytic astrocytomas and typically presents in the very young but can occur in older children and rarely in adults. A 12-years-old male presented with focal seizures, headache and vomiting of 10 days duration. Computed tomogram showed a hypo- to hyperdense and peripherally enhancing, solid-cystic lesion in the left temporal lobe. Histopathological examination revealed a characteristic tumor composed of bipolar cells arranged in dyscohesive sheets, angiocentric pattern in a loose myxoid background, with brisk mitotic activity and foci of necrosis. No Rosenthal fibers or eosinophilic granular bodies were seen. The tumor cells showed strong GFAP and scattered p53 positivity, but were negative for EMA. Ki-67 positivity ranged from 30 to 40%, highest reported till date. The patient was treated with radiotherapy and concurrent temozolamide and the tumor recurred after two years.

Pilomyxoid Astrocytoma (PMA) Shows Significant Differences in Gene Expression vs. Pilocytic Astrocytoma (PA) and Variable Tendency Toward Maturation to PA

“…It is notable that mitosis-related genes were overexpressed in PMAs versus PAs despite the known overlap between the rates in these two entities (23). The MIB-1 rates for pure PMAs in our study were not out of range of previously-reported levels (8, 12), and thus our study cohort was not skewed by cases that were exceptionally proliferative, although such cases have been reported (21). Possibly the microarray better detects modest differences in cell cycling between PMAs and PAs than does manual MIB-1 counts.…”

Hypothalamic Pilomyxoid Astrocytoma in a Child with Lipodystrophy

“…4,6 However, cases have been identified across a broad age range, even among adults. 8 Clinical presentations vary and include developmental delay, failure to thrive, vomiting, feeding difficulties, and generalized weakness. 6 In infants, the initial clinical manifestations can be more subtle, such as increased head size or bulging fontanelle from increased intracranial pressure.…”

“…9 The reported frequency of central necrosis varies; some authors believe it to be rare, while a large review of cases noted necrosis in nearly one-third of tumors. 8,11 Peritumoral edema is infrequently seen. 12 PMAs tend to be devoid of calcifications and do not demonstrate reduced diffusivity, helping distinguish them from craniopharyngiomas and germinomas, respectively.…”

Spontaneous Malignant Transformation of a Pilocytic Astrocytoma of Cerebellum

“…In the majority of published case reports, patients had received previous radiotherapy. 4 , 9 , 11 , 12 Therefore, this therapy has been considered a key factor for malignant changes, despite there being no available information about cumulative incidence, risk factors, and molecular abnormalities. 7 Malignant transformation without previous radiotherapy has also been reported but occasionally in a pediatric age and in locations other than the cerebellum.…”