Protoplasmic astrocytoma

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Synonyms and keywords: Protoplasmic astrocytomas; Diffuse astrocytoma; Low grade astrocytoma

Overview

Protoplasmic astrocytoma is a rare variant of diffuse low grade astrocytoma with characteristic histological and imaging features. It has been suggested that protoplasmic astrocytoma represents a variant of dysembryoplastic neuroepithelial tumors (DNET), as they share histologic and imaging features. Currently, protoplasmic astrocytoma is classified as a subtype of diffuse low-grade astrocytoma.[1]

Pathophysiology

Gross Pathology

Microscopic Pathology

  • On microscopic histopathological analysis, protoplasmic astrocytoma is characterized by:[2][3]
  • Neoplastic protoplasmic astrocytes
  • Scant cytoplasm
  • Rounded prominent nuclear contour
  • Flaccid processes
  • Low cellular density
  • Mild nuclear atypia (enlarged, irregular contour, hyperchromasia, and coarsened nuclear chromatin pattern)
  • Mucinous fluid containing microcystic spaces (prominent feature)
  • Abscence of mitoses, microvascular proliferation, and necrosis

Immunohistochemistry

  • Protoplasmic astrocytoma is demonstrated by positivity to tumor marker such as GFAP.[2]

Differentiating Protoplasmic Astrocytoma from other Diseases

  • Protoplasmic astrocytoma must be differentiated from:[4]

Epidemiology and Demographics

Age

  • Protoplasmic astrocytoma is a rare disease that tends to affect young adults.[5]
  • The mean age at diagnosis is 32 years.

Gender

  • Males are more commonly affected with protoplasmic astrocytoma than females. The male to female ratio is approximately 1.67 to 1.[5]

Natural History, Complications and Prognosis

Natural History

  • If left untreated, patients with protoplasmic astrocytoma may progress to develop seizures, focal neurological deficits, and hydrocephalus.[6]
  • Protoplasmic astrocytoma is a slow growing tumor with an indolent course.

Complications

  • Common complication of protoplasmic astrocytoma include:[6]

History and Symptoms

History

  • When evaluating a patient for protoplasmic astrocytoma, you should take a detailed history of the presenting symptom (onset, duration, and progression), other associated symptoms, and a thorough family and past medical history review.

Symptoms

  • Symptoms of protoplasmic astrocytoma include:[6]

CT

  • Head CT scan is helpful in the diagnosis of protoplasmic astrocytoma. On CT scan, protoplasmic astrocytoma is characterized by:[7]
  • Hypodense mass
  • Positive mass effect
  • No enhancement
  • Cystic or fluid attenuation, due to the aforementioned prominent mucinous microcystic component

MRI

  • Brain MRI is helpful in the diagnosis of protoplasmic astrocytoma. On MRI, protoplasmic astrocytoma is characterized by:[7][8]
MRI component Findings

T1

  • Hypointense compared to white matter

T2

  • Hyperintense compared to white matter

Fluid-attenuated inversion recovery (FLAIR)

  • Large areas of T2 hyperintensity suppress on FLAIR
  • These are not macrocystic, but rather represent the areas with abundant microcystic change

T1 with contrast

  • Little or no enhancement

Diffusion weighted imaging (DWI)

  • No restricted diffusion

Other Imaging Findings

Magnetic Resonance Spectroscopy

Magnetic Resonance Perfusion

  • MR perfusion may be helpful in the diagnosis of protoplasmic astrocytoma, which demonstrates no elevation of relative cerebral blood volume (rCBV).[7]

Electroencephalogram

  • Electroencephalogram (EEG) is performed in cases of protoplasmic astrocytoma to record the continuous electrical activity of the brain and locate the seizure activity.[9]

Biopsy

  • Biopsy of the protoplasmic astrocytoma tumor, taken through a needle during a simple surgical procedure, helps to confirm the diagnosis.[10]

Treatment

  • The treatment of protoplasmic astrocytoma depends on the clinical presentation, tumor size, and location.[10]
  • Surgery: The predominant therapy for protoplasmic astrocytoma is surgical resection.[10]
  • Radiotherapy: Radiotherapy may be used in protoplasmic astrocytoma post-operatively or at the time of recurrence or progression.[11]
  • Chemotherapy: Chemotherapy may have a role in recurrent and de-differentiated tumors.[11]


 
 
 
 
 
 
 
 
 
 
 
 
Treatment of protoplasmic astrocytoma
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Surgery
 
 
 
Radiotherapy
 
 
 
Chemotherapy
 
 
 
 
 
 
 
 
 
 
 
 
 

References

  1. ↑ Protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  2. ↑ 2.0 2.1 2.2 Pathology of protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  3. ↑ Pathology of low grade infiltrative astrocytoma. Dr Ahmed Abd Rabou and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/low-grade-infiltrative-astrocytoma. Accessed on January 8, 2016
  4. ↑ Differential diagnosis of low grade infiltrative astrocytoma. Dr Ahmed Abd Rabou and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/low-grade-infiltrative-astrocytoma. Accessed on January 5, 2016
  5. ↑ 5.0 5.1 Epidemiology of protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  6. ↑ 6.0 6.1 6.2 Clinical presentation of protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  7. ↑ 7.0 7.1 7.2 7.3 Radiological features of protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  8. ↑ Radiographic features of low grade infiltrative astrocytoma. Dr Ahmed Abd Rabou and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/low-grade-infiltrative-astrocytoma. Accessed on January 8, 2016
  9. ↑ Radiographic features of fibrillary astrocytoma. Dr Henry Knipe and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/fibrillary-astrocytoma. Accessed on January 4, 2016
  10. ↑ 10.0 10.1 10.2 Treatment and prognosis of protoplasmic astrocytoma. Dr Bruno Di Muzio and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/protoplasmic-astrocytoma. Accessed on January 8, 2016
  11. ↑ 11.0 11.1 Treatment and prognosis of low grade infiltrative astrocytoma. Dr Ahmed Abd Rabou and A.Prof Frank Gaillard et al. Radiopaedia 2016. http://radiopaedia.org/articles/low-grade-infiltrative-astrocytoma. Accessed on January 8, 2016

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