A case presentation impressively demonstrated that other tumors can metastasize within a meningioma. So you have to look closely at what it is when you come across a meningioma.
(ag) An astonishing case was recently presented in the Journal of Clinical Endocrinology & Metabolism [1]: A 60-year-old woman with progressive, iodine-refractory thyroid carcinoma with skeletal and pulmonary metastases developed right-sided ataxia. Intracranial metastasis was suspected. Scintigraphy after the sixth run of I-131(radioiodine) therapy had identified a new lesion of the posterior cranial fossa. Magnetic resonance imaging of the brain showed a dura-resident mass over 20 mm in diameter in the posterior fossa, suggestive of meningioma.
With a tentative diagnosis of metastasis to the posterior fossa, treatment changed from prednisolone to dexamethasone 4 mg twice daily. This medication was maintained until metastasectomy one month later.
Histopathology revealed a WHO grade I meningioma. Interestingly, this meningioma contained a metastatic, poorly differentiated thyroid carcinoma. Although the patient had a symptomatic response to metastasectomy and external beam radiotherapy, she died a year later from complications of cauda equina syndrome.
A tumor within a tumor
Undiagnosed thyroid cancer may present as intracranial metastases mimicking meningioma [2]. Thus, it is important to more closely examine a lesion that appears benign at first glance. Meningioma is the most common intracranial tumor that harbors metastases (often from the lung and breast) [3].
Thyroid cancer and meningiomas are similar in biological, metabolic, molecular, and hormonal factors. However, the exact mechanism behind tumor-to-tumor metastases is unknown. Meningiomas themselves (without thyroid cancer) may show iodine affinity on scintigraphy due to edema and high vascularity.
What is the finding?
The authors note that this is the first published case of poorly differentiated thyroid carcinoma metastasizing inside an intracranial meningioma that developed from a multifocal mixed thyroid cancer.
Although meningiomas can physiologically concentrate I-131, their case, according to the authors, shows that the exclusion of metastases from a potentially more dangerous primary tumor in an apparently benign lesion is of great importance.
Literature:
- Ling M, et al: Tumor within Another Tumor: An Unusual Case of Metastatic Poorly Differentiated Thyroid Carcinoma within an Intracranial Meningioma. J Clin Endocrinol Metab 2014, doi: 10.1210/jc.2014-1310.
- Portocarrero-Ortiz L, et al: Thyroid follicular carcinoma presenting as skull and dural metastasis mimicking a meningioma: a case report. J Neurooncol 2009; 95: 281-284.
- Moody P, et al: Tumor to tumor metastasis: pathology and neuroimaging considerations. J Clin Exp Pathol 2012; 5(4): 367-373.
InFo Oncology & Hematology 2014; 2(7): 3-4.
