Our patient had an original diagnosis of atypical (grade II) meningioma with metastases to the liver two years after initial resection. Briefly, meningiomas are graded on a scale of I-III. Grade II meningiomas are characterized by the presence of either clear cell or chordoid morphology or features of an atypical meningioma (1). The histologic finding alone of either 4-19 mitotic figures/10 HPF OR brain invasion is diagnostic of atypical meningioma, but the diagnosis can also be made if three of the following histologic features are present: increased cellularity, small cells with high nuclear to cytoplasmic ratio, prominent nucleoli, patternless/sheetlike growth or geographic necrosis (1). Grade III meningiomas are characterized by the presence of rhabdoid or papillary morphology or features of an anaplastic meningioma, including 20+ mitotic figures/10 HPF or sarcomatous/carcinomatous histology 9 (1).
Extracranial metastases of meningioma are rare, occurring in approximately 0.1% of cases, but is more commonly seen in atypical or anaplastic meningiomas (2-4). In a series of 115 cases of extracranial metastases in meningioma, 19% were atypical and 31% were anaplastic (4). The most common location for distant metastases is the lung, but has also been reported in bone, liver, pleura, and even cervical lymph nodes (2-4). Other risk factors for extracranial metastases of meningioma include: previous craniotomy, venous sinus invasion, local recurrences, and papillary morphology (3). Extracranial metastases can precede and/or coincide with a diagnosis of intracranial meningioma (3). EMA can be negative in grade II/III meningiomas, but somatostatin receptor 2a (SSTR2a) can be useful in these cases as it is a highly sensitive and specific marker that demonstrates strong, diffuse nuclear and cytoplasmic staining in high-grade meningiomas (5).