Meningioma

Question 1

What are the four critical histopathological variables for meningioma?

Answer 1

1. Grade;
2. Histological subtype;
3. Proliferation indices;
4. Brain invasion.

Question 2

Name 8 WHO grade I meningiomas with low recurrence risk.

Answer 2

1. Meningothelial (syncitial), most common;
2. Fibrous (fibroblastic);
3. Transitional (intermediate between meningothelial and fibrous);
4. Psammomatous;
5. Angiomatous;
6. Microcystic;
7. Secretory;
8. Lymphoplasmacyte-rich.

Question 3

Name 3 WHO II or III meningiomas with greater recurrence risk and/or aggressive growth.

Answer 3

1. Atypical;
2. Rhabdoid;
3. Malignant (anaplastic; papillary; sarcomatous).

Question 4

Do proliferation indices correlate with prognosis?

Answer 4

Yes. Examples are Ki-67 and MIB-1. Should not however be used as the sole determinant of grading.

Question 5

Is presence of brain invasion an indicator of malignancy in meningiomas?

Answer 5

No. It does increase the likelihood of recurrence though, to levels similar to atypical meningiomas.

Question 6

What are the histopathological features of meningothelial meningiomas?

Answer 6

1. Lobules of tumour cells demarcated by thin collagenous septae;
2. Mostly uniform cells, like normal arachnoid cap cells;
3. Whorls and psammoma bodies are not common.

Question 7

What are the histopathological features of fibrous meningiomas?

Answer 7

1. Spindle cells forming bundles;

2. Wide fascicles with varying amounts of intercellular collagen.

Question 8

What are the histopathological features of transitional meningiomas?

Answer 8

1. Both meningothelial and fibrous patterns;
2. Lobular and fascicular arrangements;
3. Tight whorls and psammoma bodies.

Question 9

What are the histopathological features of microcystic meningiomas?

Answer 9

Characterised by cells with thin elongated processes encompassing microcysts containing pale, eosinophilic mucinous fluid.

Question 10

What are the histopathological features of secretory meningiomas?

Answer 10

Presence of ‘pseudopsammoma bodies’, focal epithelial differentiation in the form of intracellular lumina containing PAS-positive eosinophilic secretions.

Question 11

What are the histopathological features of atypical meningiomas?

Answer 11

Increased mitotic activity, with three or more of the following features:

1. Increased cellularity;
2. Small cells with high nuclear:cytoplasm ratio;
3. Prominent nucleoli;
4. Uninterrupted patternless or sheet-like growth;
5. Foci of necrosis.

Question 12

What are the histopathological features of rhabdoid meningiomas?

Answer 12

1. Sheets of rhabdoid cells;

2. High proliferative indices.

Question 13

What are the histopathological features of malignant meningiomas?

Answer 13

1. Obvious malignant cytology resembling carcinoma, melanoma or high grade sarcoma;
2. Markedly elevated mitotic index (20+/HPF).