Hyperplastic intradiploic meningothelial tissue in the orbital roof mimicking metastatic disease.

Osteolytic lesions are highly suggestive of metastatic disease or in rare instances may result from primary extradural meningiomas. Herein, we describe a rare case of a patient who presented with a large area of osteolysis on the right orbital roof. An excisional biopsy revealed that the lesion was associated with the presence of hyperplastic intra-osseous meningothelial tissue. To our best knowledge, this is the first evidence that ectopic nonneoplastic meningothelial cells may induce osteolysis on the orbital walls.