Microcystic meningioma with late-phase accumulation on thallium-201 single-photon emission computed tomography: case report.
WHO classification of meningiomas (adapted after Louis et al., 2016)  Meningioma WHO grade Histological type Meningothelial meningioma Fibrous meningioma Transitional meningioma WHO grade I Psammomatous meningioma Meningioma Angiomatous meningioma Microcystic meningioma Secretory meningioma Lymphoplasmacyte-rich meningioma Metaplastic meningioma WHO grade II Chordoid meningioma Meningioma Clear cell meningioma (intracranial) Atypical meningioma WHO grade III Papillary meningioma Meningioma Rabdoid meningioma Anaplastic (malignant) meningioma Table 2.
The error was in misinterpreting microcystic meningioma (WHO grade I) as a malignant neoplasm or high-grade tumor, and misdiagnosing central neurocytoma (WHO grade II) as a low-grade glioma.
A case of microcystic meningioma (WHO grade I) was reported as a malignant neoplasm in FS [Figure 5 a and b].
Frozen section Permanent section n Low-grade glioma Central neurocytoma 1 Malignant neoplasm Microcystic meningioma 1 (grade I) Ependymoma Medulloblastoma 1 Ependymoma Choroid plexus 1 papilloma Low-grade glioma Anaplastic astrocytoma 3 (grade III) Small round blue cell Glioblastoma 1 tumor Total 8 Table 5: Cases where the frozen section reports were nonrepresentative and a final diagnosis was deferred to the permanent section.
 Microcystic meningioma is named because of its microcystic appearance that occurs owing to the variable-sized intercellular vacuole.
Microcystic meningioma. Clinicopathologic report of eight cases.
of cases Percentage of cases Transitional meningioma 52 58.4% Meningothelial meningioma 11 12.4% Psammomatous meningioma 09 10.1% Angiomatous meningioma 06 6.7% Atypical meningioma 04 4.5% Fibroblastic meningioma 03 3.4% Anaplastic meningioma 01 1.1% Microcystic meningioma
01 1.1% Secretory meningioma 01 1.1% Metaplastic meningioma 01 1.1% TOTAL 89 100% TABLE No.