General
- “Circumscribed” referring to their more solid growth pattern, as opposed to the inherently “diffuse” tumors in the above 3 adult and paediatric groups
Consist of
Comparison
Pilocytic astrocytoma vs PXA
Feature | Pilocytic Astrocytoma | Pleomorphic Xanthoastrocytoma |
Definition | An astrocytoma with classic histological features such as biphasic compact growth patterns (compact bipolar cells with rosenthal fibres), loose growth patterns (loose, textured multipolar cells with micro cyst), piloid cytology, low proliferative activity, with or without Rosenthal fibres and/or eosinophilic granular bodies. A low-grade piloid astrocytic neoplasm with a solitary МАРК alteration, such as KIAA1549-BRAF fusion. | An astrocytic glioma with large pleomorphic and frequently multinucleated cells, spindle and lipidized cells, a dense pericellular reticulin network and numerous eosinophilic granular bodies. |
Prevalence | Most common CNS neoplasm of childhood. | Rare, 1% of all primary brain tumours. |
Age | Peak age 8 - 13 years. May arise in adults but very rare. | Mean age 25 years. |
Gender Ratio | M:F same. | M:F = 1:1. |
Genetic Profile | Mitogen-activated protein kinase (MAPK) pathway alterations, BRAF mutation forming fusion protein (KIAA1549:BRAF), associated with noonan syndrome (neuro-cardio-facial-cutaneous syndrome), associated with NF1. | BRAF V600E point mutation, constitutionally activated BRAF → MAPK signaling, no IDH mutation. |
Grading | WHO grade I. | Grade 2 unless there is high mitotic index or necrosis then becomes Grade 3: PXA with anaplastic features. |
Location | Usually involves midline structures. Paeds: infra-tentorial region. | Superficial meningocerebral location (leptomeninges and cerebrum), 98% arise supratentorially, preferential temporal lobe involvement. |
Radiology | Well circumscribed, large tumour cyst with a contrast enhancing wall and mural nodules. Contrast enhancement is variable. | Cystic with a frequent cyst mural nodule architecture, strong contrast enhancing. |
Pathology | Characterized by a biphasic pattern with varying proportions of piloid areas alternating with spongy areas. Bipolar neoplastic cells with elongated hair-like processes that are arranged in parallel bundles and resemble mats of hair (knotted hair). | Pleiomorphic(Greek many forms): variable histological appearance of tumour, spindled cells are intermingled with mononucleated or multinucleated giant astrocytes, nuclei show variation in size and staining. |
Management | Surgery | Surgery is the treatment of choice for PXAs and PXA associated epilepsy. Chemotherapy (Alkylating chemotherapy, BRAF inhibitor vemurafenib). Radiotherapy and treatment with alkylating chemotherapy for anaplastic PXA. |
Prognosis | Better prognosis than diffuse types, particularly if resectable (such as cerebellar tumours). 5 yrs and 10 yrs survival >95% after surgical resection. | Gross total resection usually eliminates seizures. 5 yr overall survival 90.4%. |
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