title: Intracranial collision tumor mimicking an octreotide-SPECT positive and FDG-PET negative meningioma.
abstract: OBJECTIVE/IMPORTANCE: Cancer metastasis to a pre-existing intracranial tumor is rare, but several cases have been reported. We report an unusual case of a "collision tumor" consisting of a renal cell carcinoma metastasis to an intracranial meningioma.
  
  
  METHODS
  A 67-year old male with renal cell carcinoma had an asymptomatic right posterior frontal dural-based lesion identified on a screening CT scan. MRI characteristics of the tumor were consistent with meningioma. On octreotide-SPECT and F-18 fluorodeoxyglucose (FDG)-PET scans, the lesion showed octreotide uptake but did not accumulate FDG, both of which are consistent with a diagnosis of benign meningioma. One week later, he presented with a 1-day history of progressive left-sided weakness. The intracranial tumor was resected, and subacute subdural blood was found overlying a soft, reddish tumor. Microscopic examination was consistent with renal cell carcinoma with a minor portion consisting of meningioma. The meningothelial component was strongly immunoreactive to vimentin and weakly reactive to epithelial membrane antigens. Neither area reacted with glucose transporter-1 (GLUT-1), correlating with low FDG-PET uptake.
  
  
  CONCLUSIONS
  Collision tumor involving metastatic renal cell carcinoma to an intracranial meningioma is a rare occurrence. Diagnosis by non-invasive means, with use of a combination of octreotide-SPECT and FDG-PET may not accurately reflect the malignant component of such a collision tumor. In this case, the collision tumor also demonstrated a propensity to undergo spontaneous hemorrhage. A high degree of suspicion of intracranial metastasis should be maintained for patients who have known systemic cancer and are found incidentally to have a dural-based mass lesion.
authors.affiliation: Department of Neurosurgery, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Chahlavi
authors.forename: Susan M
authors.initials: SM
authors.lastname: Staugaitis
authors.forename: Raafat
authors.initials: R
authors.lastname: Yahya
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vogelbaum
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary*; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000473:pathology*; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008579:Meningioma / Q000000981:diagnostic imaging / Q000556:secondary*; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18