Subependymoma and dysembryoplastic neuroepithelial collision tumor in the foramen of Monro: case report.

Intracranial collision tumors have rarely been reported in the literature and generally include at least 1 malignant tumor component. Subependymoma with dysembryoplastic neuroepithelial tumor (DNET) is an as-yet unreported combination. Both components are uncommon tumors, and presentation in the foramen of Monro is even more unusual. A 16-year-old male patient with a past medical history significant for asthma presented with a 3-month history of headaches and radiographic evidence of mild obstructive hydrocephalus secondary to a nonenhancing ventricular lesion at the foramen of Monro. He underwent endoscopic biopsy and resection. Pathological analysis revealed distinct components of subependymoma and DNET. At the 1-year follow-up, the patient was doing well without regrowth of tumor. The authors describe a case of intracranial collision tumor demonstrating 2 grade I components: a novel combination of subependymoma and DNET.