P10.19 Pure aqueductal tumors: A rare entity

Abstract

Pure aqueductal tumors are completely different from tectal or tegmental tumors, and they indeed exist just within the aqueduct. We report our unique cases of pure aqueductal pilocytic astrocytoma (aPA) and rosette-forming glioneuronal tumor (aRGNT), and then we reviewed the pure aqueductal tumors by literatures. In our 18 years old aPA case, he had been followed by NF-1 in dermatology, and was pointed out mild enlargement of the lateral and third ventricle by MRI three years ago. There was no obvious cause of enlargement of ventricles at that time. A year ago, he showed transient mild headache and MRI showed progression of enlargement of the ventricles, and MRI showed small tumor located within the aqueduct. Because a tumor size showed enlargement gradually after that, endoscopic third ventriculostomy (ETV) and tumor biopsy was performed at the same time, and pathological diagnosis was typical type of pilocytic astrocytoma (Ki-67: 0.3%). After the operation, he was asymptomatic and showed a good course. Although the tumor size has increased, it is stable now and being carefully observed without any chemo-radio therapy. In our 28 years old aRGNT case, he had complained intermittent mild headache. MRI showed the tumor located within the aqueduct. ETV and tumor biopsy was performed at the same time, and pathological diagnosis was RGNT (Ki-67: 0.6%). After the operation, he was asymptomatic and showed a good course. Six months later, MRI showed the enlargement of tumor extended to the fourth ventricle. Tumor removal by craniotomy was performed by suboccipital approach. After the operation, he showed a good course. Pure aqueductal tumors are very rare. Because aqueductal tumors combine a hydrocephalus and also show several pathological diagnoses, perform the ETV plus biopsy at one time is effective. Pure aPA have been reported only 3 cases from the past papers. Among these 3 cases, 2 cases comorbid the NF-1 such as our case. Although typical tectal pilocytic astrocytomas are usually stable by normal observation, pure aqueductal tumors need careful observation because they sometimes show uncharacteristic growing in spite of low score of Ki-67 index.