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CASE REPORT Table of Contents   
Year : 2010  |  Volume : 53  |  Issue : 2  |  Page : 294-296
Pilomyxoid astrocytoma


1 Department of Pathology, Shri Mahant Indresh Hospital, Shri Guru Ram Rai Institute of Health & Medical Sciences, Patel Nagar, Dehradun, India
2 Department of Radiology, Shri Mahant Indresh Hospital, Shri Guru Ram Rai Institute of Health & Medical Sciences, Patel Nagar, Dehradun, India
3 Department of Neurosurgery, Shri Mahant Indresh Hospital, Shri Guru Ram Rai Institute of Health & Medical Sciences, Patel Nagar, Dehradun, India

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Date of Web Publication12-Jun-2010
 

   Abstract 

Pilomyxoid astrocytoma (PMA) is a recently described brain tumor. PMA shares similar features with pilocytic astrocytoma (PA), the most common central nervous system (CNS) tumor in the pediatric population, yet displays subtle histologic differences. We describe a case of PMA in a six-year-old male involving sellar and suprasellar region presenting with failure to thrive and delayed developmental milestones. The histological findings revealed a tumor composed of a monotonous population of loosely arranged cells with delicate piloid like processes, within a prominent myxoid background. The tumor lacked biphasic appearance, Rosenthal fibers, eosinophilic granular bodies and calcification that are commonly observed in classical PA. Previous studies have shown PMA to behave more aggressively than PA, with shorter progression-free survival as well as a higher rate of recurrence and CNS dissemination. Thus, recognition of PMA and its distinction from classical PA is very important.

Keywords: Central nervous system, pediatric, pilomyxoid astrocytoma, tumor

How to cite this article:
Azad S, Kudesia S, Chawla N, Azad R, Singhal M, Rai SM, Arora P. Pilomyxoid astrocytoma. Indian J Pathol Microbiol 2010;53:294-6

How to cite this URL:
Azad S, Kudesia S, Chawla N, Azad R, Singhal M, Rai SM, Arora P. Pilomyxoid astrocytoma. Indian J Pathol Microbiol [serial online] 2010 [cited 2020 Sep 23];53:294-6. Available from: http://www.ijpmonline.org/text.asp?2010/53/2/294/64283



   Introduction Top


Pilomyxoid astrocytoma (PMA) is a recently described central nervous system (CNS) tumor of pediatric age group found mainly in the chiasmatic- hypothalamic region. This entity was described in 1999 and distinguished from pilocytic astrocytomas (PAs). [1] In recent World Health Organization (WHO) classification of CNS tumors 2007; PMA has been added into the category of histological variants of PA. [2] This tumor behaves more aggressively, has a higher rate of metastasis throughout CNS and poorer prognosis compared to PA. To the best of our knowledge, this is the first reported case of PMA from India. Rarity of this lesion prompted us to present the clinico-radiological and pathological features of this case.

Clinical Summary

A six-year-old boy presented with vomiting, increasing head size, altered sensorium, weakness of lower limbs, loss of appetite and loss of weight. His general condition was poor with grade 4 malnutrition and delayed developmental milestones.

Radiological Findings

Contrast enhanced computerized tomography (CT) [Figure 1] and magnetic resonance (MR) imaging head revealed a large uniformly enhancing, non-calcified mass lesion in supra-sellar location apparently extending into sellar region and causing significant obstructive hydrocephalus. Signal intensity on MR was uniformly hyper intense on T2 as well as FLAIR sequences and hypo intense on T1. Differential diagnoses offered on imaging were pituitary glioma, solid craniopharyngioma and pituitary adenoma.

The patient underwent a ventriculo-peritoneal shunt with gross total excision of tumor through trans-cranial approach. He has been followed up for five months now with no clinical or radiological indication of tumor recurrence. However; the patient still suffers from grade II paraplegia and visual disturbances.

Histopathological Findings

The specimen was received as multiple grey white soft tissue fragments with mucoid material, measuring 5.5 x 4.0 x 1.0 cm. Histopathological examination of sections revealed a tumor with uniform proliferation of bipolar spindle cells having piloid cytoplasm with tapering glial fibrils and focal mild nuclear pleomorphism. The tumor was loose textured and showed microcystic changes as well as myxoid appearance in the stroma [Figure 2]a. Focal vascular proliferation and telangiectatic clusters were also seen [Figure 2]b. At places, the neoplastic cells were seen concentrated in perivascular region [Figure 3]. However; biphasic pattern, eosinophilic granular bodies, Rosenthal fibers, calcification and necrosis were absent. Histochemical staining with alcian blue highlighted the prominent myxoid background. Immuno-histochemical staining showed positivity for glial fibrillary acidic protein (GFAP) and vimentin. On the basis of these findings, a diagnosis of pilomyxoid astrocytoma was made.


   Discussion Top


Pilomyxoid astrocytoma was first recognized in 1999 as a separate entity. [1] Though PMA is a pediatric tumor found in chiasmatic-hypothalamic region; it has also been described in posterior fossa, diencephalon and spinal cord. [3],[4] Mean age at diagnosis of PMA is 18 months although it can occur at any time in childhood and rarely in adults. [4],[5] Patients usually present with failure to thrive, developmental delay, altered sensorium, vomiting and generalized weakness along with focal neurological symptoms, visual and endocrine disturbances. [3]

On CT and MR imaging, PMA usually presents as a uniformly enhancing solid mass in supra-sellar region, with associated obstructive hydrocephalus and without significant cystic areas or necrosis. On MR, highly homogenous T2 signal intensity, extension of T2 signal abnormality into deep white matter as well as grey matter along with cerebrospinal fluid (CSF) dissemination may help in differentiation from PA. [6] PMA has little or no calcification while craniopharyngioma is commonly calcified and at least partially cystic. In our case, in addition to the above mentioned classical imaging features, there was an unusual apparent sellar extension of the mass and hence pituitary adenoma was also considered as an imaging possibility. Although PMA can be considered as a possibility on the basis of above described radiological findings, the diagnosis of PMA is mainly based on histopathological examination

PMA is typically characterized by monomorphous proliferation of bipolar spindle cells present in a markedly loose myxoid stroma that can be highlighted with a histochemical stain for Alcian blue. [7] Mitosis is rare or absent. Angiocentricity of the tumor cells forming pseudorossettes is also one of the recognizable histological features. Infiltration of tumor cells into surrounding neuropil at the tumor periphery may occur in some cases. [8] Classical PA has a compact biphasic architecture demonstrating densely cellular areas alternating with loose cystic regions. In contrast, pilomyxoid astrocytoma lacks the biphasic appearance. Rosenthal fibers, eosinophilic granular bodies and calcification are also uncommon or absent. [1],[8] Microvascular changes such as telangiectatic clusters in the cyst wall and necrosis without pseudopalisading can be seen. [7] The tumor cells and fibrillary background shows strong immunopostivity for GFAP, S-100, and vimentin. [1],[2],[9] The histological and immunohistochemical findings in our case matched with most of the findings described in these studies.

Majority of the pediatric low-grade astrocytomas in hypothalamic/ chiasmatic region are classical PA. Patients have a longer progression free survival with gross total resection of the lesion. However; PMA has an aggressive behavior with a higher rate of local recurrence and substantial rate of CSF dissemination as has been reported in several studies. [6],[8] Therefore the histopathological differentiation of PMA from PA is important prognostically.


   Conclusion Top


The above case highlights the clinical, radiological and pathological features of PMA in suprasellar region apparently extending to the sellar region. It is important to separately recognize PMA from PA due to its propensity to involve younger age group and an overall higher local recurrence as well as CSF spread. Histopathological examination of the tumor tissue is the mainstay in differentiating the two entities. Increased recognition of these lesions can affect the prognosis and treatment.

 
   References Top

1.Tihan T, Fisher PG, Kepner JL, Godfraind C, McComb RD, Goldthwaite PT, et al. Pediatric astrocytomas with monomorphous pilomyxoid features and a less favourable outcome. J Neuropathol Exp Neurol 1999;58:1061-8.   Back to cited text no. 1  [PUBMED]    
2.Brat DJ, Scheithauer BW, Fuller GN, Tihan T. Newly Codified Glial Neoplasms of the 2007 WHO Classification of Tumours of the Central Nervous System: Angiocentric Glioma, Pilomyxoid Astrocytoma and Pituicytoma. Brain Pathol 2007;17:319-24.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Komotar RJ, Mocco J, Jones JE, Zacharia BE, Tihan T, Feldstein NA, et al. Pilomyxoid astrocytoma: Diagnosis, prognosis and management. Neurosurg Focus 2005;18:1-3.  Back to cited text no. 3      
4.Burger PC, Cohen KJ, Rosenblum MK, Tihan T. Pathology of diencephalic astrocytomas. Pediatr Neurosurg 2000;32:214-9.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]  
5.Komotar RJ, Mocco J, Zacharia BE, Wilson DA, Kim PY, Canoll PD, et al. Astrocytoma with pilomyxoid features presenting in an adult. Neuropathology 2006;26:89-93.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]  
6.Arslangolu A, Cirak B, Horska A, Okoh J, Tihan T, Aronson L, et al. MR imaging characteristics of pilomyxoid astrocytomas. Am J Neuroradiol 2003;24:1906-8.  Back to cited text no. 6      
7.Thomas JC. Pilocytic astrocytoma and pilomyxoid astrocytoma. In: Mclendon RE; Rosenblum MK; Bigner DD, editors. Russel and Rubinstein's Pathology of Tumors of the Nervous System. London: Hodder Arnold; 2006.p.131-45.  Back to cited text no. 7      
8.Komotar RJ, Burger PC, Carson BS, Brem H, Olivi A, Goldthwaite PT, Tihan T. Pilocytic and pilomyxoid hypothalamic/chiasmatic astrocytomas. Neurosurgery 2004;54:72-9.   Back to cited text no. 8  [PUBMED]  [FULLTEXT]  
9.Fuller CE, Frankel B, Smith M, Rodziewitz G, Landas SK, Caruso R, et al. Suprasellar monomorphus pilomyxoid neoplasm an ultrastructural analysis. Clin Neuropathol 2001;20:256-62.  Back to cited text no. 9  [PUBMED]    

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Correspondence Address:
Sheenam Azad
Department of Pathology, SGRR Medical College, Patel Nagar, Dehradun, Uttrakhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.64283

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  [Figure 1], [Figure 2], [Figure 3]



 

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