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Spontaneous malignant transformation of a supratentorial pilocytic astrocytoma. Sarabia-Herrero; M. Pilocytic astrocytoma PA is a circumscribed neoplasia considered as a grade I astrocytoma by the World Health Organization. Its most common location is the cerebellum and it develops during the first two decades of the life. Anaplastic or malignant transformation MT can rarely occur and is usually related to previous radiation. Spontaneous MT has exceptionally been reported.

Histological criteria for diagnosis of MT are unclear, so no consensus exists. We present an atypical case of MT of a frontal PA without previous radiotherapy in a 28 years old patient. Also, we review the literature about prognostic factors of PA and discuss histological features that are considered as anaplastic or malignant in the PA. Key words: Pilocytic astrocytoma. Malignant transformation.

Histologically, PA is characterized by a biphasic pattern: in one, there are compact zones constituted by strongly glial fibrillary acidic protein GFAP inmunopositive bipolar cells with Rosenthal fibers, and, on the other, microcystic areas that contain weakly GFAP-positive multipolar cells with eosinophilic granular bodies Occasional mitoses, hyperchromatic and pleomorphic nuclei and glomeruloid vascular proliferation may appear, but they are not considered signs of malignancy 37, On MRI PA is generally a well-demarcated, either oval or round mass that is constituted by a cyst and mural nodule.

Solid component is hipointense relative to gray matter in T1-weighted images and hyperintense relative to gray matter in T2-weighted images. After gadolinium administration the mural nodule intensely, heterogeneously enhances 25,31 while most cyst walls do not One of the main prognostic factors related to outcome is the degree of resection 15,22, Those tumours undergoing a gross-total resection have a significantly better prognosis than those with subtotal resection 15,22, Radiotherapy has a limited therapeutic role and is indicated when tumours are surgically inaccessible, in multicentric PAs, anaplastic recurrence or significant residual postoperative tumour 15,26, Sometimes an unfavourable evolution can occur.

This feature is characterized by phenomenons such as local recurrence, multicentric disease, leptomeningeal dissemination or malignant transformation MT 15,16, Anaplastic or malignant transformation of PA is a rare event described in the literature Radiation therapy may be related with this anaplastic change because most of such tumours had been previously irradiated 14,33, However, pathological criteria for classifying PAs with atypical features are unclear 33, We describe a case of MT of a PA located in frontal lobe without previous radiotherapy.

We review the literature about prognostic factors related with PA and the evolution of this tumour. Lastly, we discuss features that are related with anaplastic transformation in PA. This 25 year old patient was first admitted to our service referring lancinating pain in the left side of his neck for two weeks and double vision on left lateral gaze since 5 days before his admission. He did not refer headache or other neurological symptoms.

Neurological examination only evidenced a left VI cranial nerve palsy. Cranial computed tomography and MRI with and without contrast enhancement, showed a voluminous right frontal cystic tumour with nodule and mural enhancement Figure 1. He was operated through a right pterional approach and a complete excision of the tumour was achieved without complications. He was discharged asymptomatic. The tumour was pathologically diagnosed as PA, with some necrotic and brain infiltration areas, but no mitosis nor atypical features were found Figures 2 and 3.

Figure 1. Axial postcontrast MRI showing cystic right frontal tumour with gadolinium enhancing nodule. Figure 2. Air dried smears stained with Diff Quick 20x Romanowsky type stains. Bipolar neoplastic cells with elongated hair-like processes. The nuclei are round to oval with open chromatin and indistinct nucleoli.

Lack of substantial pleomorphysm. Figure 3. Obtained material smeared on slide, alcoholfixed and stained with Hematoxylin-Eosin 20x. Observe multiple nuclei within large or giant cells. There is no mitosis nor necrosis nor vascular proliferation. He was followed on an ambulatory basis for the next 3 years, with no evidence of persistence or recurrence of the tumour on imaging. The MRI disclosed a rapidly growing recurrent cystic tumour on the right frontal region Figure 4.

He was operated again through the same previous right pterional craniotomy and a complete excision could be achieved although this time, the sylvian artery branches were surrounded and involved by tumour, making resection less straightforward but without complications. The patient was discharged neurologically asymptomatic on anticonvulsants. He was submitted to the Radiotherapy Service where he was complementary treated with whole brain radiation therapy.

Figure 4. Axial contrast enhanced MRI displays cystic tumor with nodule at the same location. Figure 5. Hematoxylinn-Eosin stained biopsy material 10x showing malignant degeneration with hypercellularity, higher cellular pleomorphysm and mitotic figures. Figure 6. Hematoxylin-Eosin stained biopsy material 20x of the malignant degeneration tumour showing hypercellularity, endothelial proliferation and focal necrosis.

He was followed for the next 30 months, with no remarkable events but some scarce epileptic seizures and imaging studies remained without visible recurrence but some small enhancing punctuate lesions scattered in both cerebral hemispheres and brainstem that progressively appeared and were interpreted as reactive radiotherapy changes. At this time the patient suffered a new rapid neurological deterioration and was readmitted presenting right hemiplegia and aphasia secondary to a frontoparietal parasagittal subcortical expansive lesion affecting the corpus callosum, which enhanced homogeneously on MRI.

The MR spectroscopy was compatible with radionecrosis. No amelioration was obtained with dexamethasone. He was operated through a frontoparietal left craniotomy, excising the necrotic tissue and the pathological diagnosis confirmed radio-necrosis.

He recovered partially from his hemiplegia and aphasia, and was discharged with sequelae, that persist2 years after his third operation. The patient is still alive, 33 years old by now, but neurologically severely disabled. He is ambulatory controlled every 6 months. He developed progressive ventriculomegaly finally requiring a ventriculoperitoneal shunt this year.

In the last MR controls no recurrence of the original tumour is seen but there is evidence of leptomeningeal spread of his tumour and a new cerebellar vermian solid tumour that enhances brightly and is compatible with an astrocytic tumour by spectrometry.

This tumour has not yet been biopsied. To review the literature, a computerized search of the National Library of Medicine database of the literature published from to was undertaken. The following medical subject headings were used in combination with "pilocytic astrocytoma": "anaplastic", "malignant", "outcome" and "prognosis".

Non-English language citations were excluded. PA is a low-grade, slowly growing tumour, generally considered to have a benign course 26, It is classified as a grade I tumour by the WHO grading system, which means a neoplasm with low proliferative potential and the possibility of cure following surgical resection alone Although PA is regarded as a circumscribed neoplasm, infiltration of the surrounding parenqchyma might be demonstrated histologically 2, Malik et al 29 reported that Supratentorial hemispheric PAs, as the presented case in this report, are relatively uncommon and little information has been reported on incidence and behaviour of this location 1,5,8,17,18, In one retrospective, single institution study of 20 recurrent PAs in children, only 3 lesions were described in the cerebral hemispheres 3.

Long-term disease-free survival rates have also been reported. Various features have been considered to correlate with prognosis. One of the main prognostic factors is the grade of surgical resection. Complete resection generally implies better prognosis than partial resection. Hayostek found that gross total resection was related with improved survival and disease-free survival However, in their series of benign cerebellar astrocytomas pilocytic and nonpilocytic in children, Pencalet el al 34 reported that extent of surgical excision was not related with survival, although this feature significantly determined the risk of tumour recurrence.

Tumour location also has been related with outcome, but this may be a result of the strong correlation between the extent of resection and tumour location The best survival rates were observed in the cerebellum located PAs. Pencalet et al showed that if cerebellar PAs extended towards the brainstem "transitional forms" according to the authors , survival was lower In their series of ninety-seven patients with cerebellar astrocytomas, Sgouros et al 39 concluded that the main negative prognostic factor was the brain stem involvement.

There is some controversy over biologic behaviour of PAs in adults. Some authors like Brown et al 45 did not find differences in the prognosis of these tumours in adults.

Respect to cystic tumours, solid PAs have not been generally associated with shorter survival times 15,19,34, However, Klein et al 24 observed that cyst-nodule type of PAs were more amenable to total resection because they did not frequently affect the brainstem structures since they usually settled in a lateral cerebellar position.

No association has been generally found between proliferation indices such as MIB-1 labelling or BUdR index and outcome 20,23,28,35, The reported mean values of the MIB-1 labelling range from 0. Nevertheless, when evaluation of MIB-1 labelling indexes was restricted to partially resected tumours, there was only an insignificant trend of MIB-1 labelling higher than 2. Some PAs seed throughout the neural axis. Incidence of LD appears increased when PAs are located in the hypothalamus. Mamelak et al 30 concluded that hypothalamic PA was 23 times more likely to show dissemination than cerebellar one.

This feature might be due to their proximity to the ventricular system. LD tends to occur within 3 years of initial diagnosis.

Outcome of patients with LD is unknown


Astrocitoma pilocĂ­tico

Spontaneous malignant transformation of a supratentorial pilocytic astrocytoma. Sarabia-Herrero; M. Pilocytic astrocytoma PA is a circumscribed neoplasia considered as a grade I astrocytoma by the World Health Organization. Its most common location is the cerebellum and it develops during the first two decades of the life. Anaplastic or malignant transformation MT can rarely occur and is usually related to previous radiation.


Esencialmente, estas neoplasias exhiben una patente monomorfa que ha sido llamada pilomixoide y predomina una densa trama de fibrillas gliales con abundantes fibras de Rosenthal. Pathology and genetics of tumours of the nervous system. Lyon: IARC; Central nervous system tumors in children. Sadighi, Zsila, and John Slopis. Pilocytic astrocytoma with abundant oligodendroglioma-like component.

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