Anaplastic pleomorphic xanthoastrocytoma (APX)

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Status

Done

Definition

A pleiomorphic xanthoastrocytoma with > 5 mitosis/ 10 high power fields

Numbers

Lower frequency of BRAF V600E mutation vs PX

CNS WHO grading

Grade 3

Localization

Like PXA: supratentorial → temporal lobe

Clinical features

Seizures most → superficial

Radiology

MRI

Cystic circumscribed supratentorial mass

Contrast enhancing

Fig. 2.25 Anaplastic pleomorphic xanthoastrocytoma. Tl -weighted MRI with contrast sequences demonstrates a large non-homogeneously enhancing tumour with mass effect and moderate surrounding oedema. — Anaplastic pleomorphic xanthoastrocytoma. T1-weighted MRI with contrast sequences demonstrates a large non-homogeneously enhancing tumour with mass effect and moderate surrounding oedema.

Histopathology

A The tumour shows classic features with pleomorphic and xanthomatous (arrow) cells and

(B) brisk mitotic activity (arrows), including atypical mitoses.

C The tumour recurred 1 year later and showed remaining areas with pleomorphic morphology and

(D) monomorphous areas with epithelioid and rhabdoid cells with mitotic activity (arrows).

APX is like PX but with greater mitotic activity

Fig. 2.26 Anaplastic pleomorphic xanthoastrocytoma. A The tumour shows classic features with pleomorphic and xanthomatous (arrow) cells and (B) brisk mitotic activity (arrows). including atypical mitoses. C The tumour recurred 1 year later and showed remaining areas with pleomorphic morphology and (D) monomorphous areas with epithelioid and rhabdoic cells with mitotic activity (arrows). — Anaplastic pleomorphic xanthoastrocytoma.

Differential diagnosis

Epithelioid glioblastoma

Hard to differentiate from APX histologically and molecularly (both contain BRAF V600E mutation)
Differentiating factor: APX lack the cytological uniformity seen in epithelioid glioblastoma

Prognosis

55% 5 yr survival with/without necrosis, necrosis presence worsens survival

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