Anaplastic central neurocytoma (CN) of both lateral ventricles.
CN is a well-established pathological entity and is generally regarded as a low-grade well-differentiated neuronal tumor, with limited growth potential. Some doctors theorize CN may derive from bipotential precursor cells of the periventricular germinal matrix, which are capable of both neuronal and glial differentiation, but maintain a low proliferative potential after birth. However, there are multiple reports of local recurrence, abundant mitosis, necrosis, extraventricular extension of tumor, and even craniospinal dissemination.
Eng et al. , was the first to report clinical evidence of CN's aggressive nature; he reported two cases of craniospinal dissemination after craniotomy and subtotal resection of neurocytoma. Yasargil et al. , reported that two patients had evidence of anaplasia and were treated with radiotherapy after total excision. Those tumors did not relapse at the time of the report after a follow-up of 5-12 months. Three patients in the same study had recurrences 38-92 months after total excision and none had evidence of anaplasia. So, it is not clear if tumors with anaplasia have a higher relapse rate or if they need additional treatment. With GFAP positivity increases and vascular proliferation in CN, might suggest a more malignant course, .There have a report, the MIB-1 index tended to be higher in central neurocytoma with mitosis and necrosis, . The MIB-1 labeling index showed that a LI of 2% might be critical in determining recurrence. which MIB-1 labeling index cut-off of 2% demonstrated tumor recurrence of 63% , . In a larger of 15 central neurocytomas, an elevated MIB- labeling index was felt to be indicative of biological activity comparing histological atypia, proliferation, and clinical outcome, . Two other patients who had histological anaplasia and MIB-labeling index < 2 did not recur. So, it appears that there is a clinically more aggressive subgroup of central neurocytomas with elevated proliferative potential as determined by labeling index studies. This is testified in another case report of a patient with a recurrent central neurocytoma who had a four-fold increase in MIB labeling index after a 9-year disease free interval, . The MIB-1 labeling index at the initial resection was 0.7% compared to 3.9% at the time of relapse. McKenzie showed in a small series of 15 cases of CN that the typical criteria for grading brain tumors such as cellular pleomorphism, necrosis, mitotic activity and endothelial vascular proliferation do not correlate with MIB-1 labeling index. Moreover, he found that the proliferation index was a useful predictor of poor outcome; 4 of 15 patients had tumor recurrence and a MIB-1 labeling index >2%, . These results were reiterated in a 129 patient meta analysis which showed 48% recurrence rate for MIB-1 labeling index >3% versus12% for <3%, . In 2003, Takao et al. reported a patient who had hyperacusis, oscillating vision, and headaches, , who was found to have a large left intraventricular mass. She underwent a craniotomy and excisional biopsy of the tumor. Although there was no pleomorphism or mitotic figures, the MIB labeling index was as high as 4.6%. The patient had a recurrence after only 11 months.
The most important therapeutic modality is surgery. Tumor total resection and radiotherapy remain the main treatment options for central neurocytomas. The effect of chemotherapy on central neurocytomas has uncertain curative effect. Long-term responses to chemotherapy have not yet been reported. Total resection was suggested to be the best treatment for patients with atypical central neurocytomas, and that postoperative radiotherapy appeared to improve both local control and survival in patients who could not safely undergo total tumor resection .
The concept that central neurocytomas are benign is not entirely correct and is questioned. Of hundreds of CN reported to date, the incidence of recurrence is low, which makes aggressive forms of this tumor difficult to study. In our case in particular, there was mitoses, nuclear atypia, necrosis and microvascular proliferation appears to be primary, likely correlates with a high MIB-1 labeling index of 10%, display atypical behavior, and finally made the patient die for the tumor recurrence. Our case is an example of a more aggressive CN, we designate anaplastic neurocytoma, WHO grade III is appropriate.
Contributed by Liao Qiu-lin, MD, Chen Xiao-dong, MD, Peng Da-yun, MD