Iatrogenic metastasis of a benign meningioma to the periosteum at the site of previous craniotomy: a case report.

Metastasis formation after resection of meningiomas is a rare event, predominantly occurring with malignant phenotypes. As far as we know, the presented case is the first report in the literature of iatrogenic seeding of a benign meningioma to the scalp following surgery. A 37-year-old woman was admitted because of a relapsing meningioma in the frontal lobe. In 1997, she had undergone complete excision of an atypical meningioma in same location. At follow-up, three new masses were found: a bifrontal meningioma on the edge of the falx, a smaller one in the falx just under the saggital sinus and a small mass, believed to be ectopic, in the periosteum at the site of the previous craniotomy. Surgical therapy was indicated. Histologically, the ectopic tumor was an atypical meningioma, similar to the one excised 10 years previously, with no relation to the other two intracranial masses. Because of the histological similarity and the location in the old craniotomy, the ectopic tumor was believed to have developed from an implantation metastasis as a consequence of the first surgery. The authors suggest that strict adherence to oncological principles should be applied in the case of benign neoplasms in order to prevent contamination of wounds with tumor cells and potential recurrence.