Liponeurocytomas are rare cerebellar neoplasm with benign histological features and a favorable clinical prognosis. However, current clinical opinion is based on a total of approximately 40 published cases
(2,7,9,12). The current WHO classification assigns the cerebellar liponeurocytoma to grade II, because recurrences have been reported in 62% of cases
(9). There have been a number of recurrences, with a mean time from diagnosis to first local recurrence presentation of 10,6 (range 10-12) years
(12,13). Despite being clinically progressive, recurrent liponeurocytomas did not show histological features of malignant progression
(9).
Liponeurocytomas are characterized by many lipidized cells found in clusters or scattered between small neoplastic cells. Immunohistochemical staining has demonstrated that both neuronal and glial differentiation. Histologically mitotic activity and proliferation rate are generally low in these lesions(9,12,13). There have been only two reported cases with histopathologic aggressive features in the literature(1,4,8,14)
Cerebellar liponeurocytoma has a relatively benign clinical course and a recurrence may appear after a long period of time with a histology only slight more aggressive than that of the original tumor(8).
Jenkinson reported an unusual case of cerebellar liponeurocytoma that presented a first recurrence 12 months after subtotal removal followed by external beam radiation therapy of the first lesion and, a second recurrence three months after a second surgical removal. Despite the absence of atypical histological features in both the primary and the relapsed tumors, the aggressive case described by Jenkinson suggested that cerebellar liponeurocytoma may not be as benign as previously thought(7).
A review of published cases indicates that 2 cases with several relapses and histopathologic aggressive features such as atypia, mitoses, necrosis and/or a high proliferation index. Both glial and neuronal differentiation were shown in all of them, as in present case (Table 1)(1,4,8,14).
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Table 1: The review of previously reported clinically and histopathologically aggressive liponeurocytomas including the present case. |
In Jouvet's case report, the recurrence was histologically identical to the original tumor in some areas but with fewer adipose-like cells, while others presented an endocrine architecture with oligodendroglia-like or monomorphic cells. Proliferation index was quite high (10-15%), and had a more likely habit of recurrence (15-30%)(8).
Gallina et al. reported the another recurred cerebellar liponeurocytoma showing clinical and histopathological aggressive features. Some differences were observed between primary lesion and its recurrence. Mitoses and MIB-1 positive cells were elevated from rare to 2-3 and from 15% to 20%. Ultrastructurally detectable synaptic vecicles were found in the recurrence, but absent in the primary tumor. Areas of micronecrosis, microhemorrhage and moderate vascular hyperplasia were observed in the relapse(1,4,14).
Our case which has occurred 3 times after the first radical excision of the primary lesion after 9, 15, and 18 years respectively. Histopathologic aggressive features like presence of mitoses, necrosis and endothelial proliferation were shown both in last two recurrent tumors. MIB-1 antibody was 33% in last surgery specimen. Therefore this findings was regarded to be reflecting its aggressiveness by multiple recurrences. Because of the rarity of the tumor, the natural history of cerebellar liponeurocytoma has not yet been defined and benign nature of the tumor is being questioned(3,4). Cerebellar liponeurocytomas may not be as benign as the current literature. Their typical low–grade cytological and histological features may hide their ominous clinical course(11).
Cluster analysis of the cDNA expression data of 1176 genes grouped cerebellar liponeurocytomas close to central neurocytomas, but distinctive from medulloblastoma. Furthermore, the cDNA expression array data suggest a relationship to central neurocytomas, but the presence of the TP53 mutations (20%), which are absent in central neurocytomas, suggest that their genetic pathways are different(4,6,9). The p53 protein was detected in our case.
The most important differential diagnosis is that of medulloblastoma with lipidized cells. In these lesions, the adipose tumour cells are usually more diffusely distributed. Lipidized medulloblastomas also occur in children. The frequency of p53 missense mutations is higher than in medulloblastomas(9).
Total resection is considered the optimal treatment. There is no consensus regarding the treatment of liponeurocytoma, specifically whether chemo- and/or radiotherapy is an indispensable part of the postoperative treatment regimen(3,4,7,9,12).
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