[Identification of a Family with SUFU Germline Deletion Based on a Case of Desmoplastic Medulloblastoma in an Infant]

Abstract

Background: Medulloblastoma, an embryonal neuroectodermal tumor of the cerebellum, is the most common malignant brain tumor in children. There are approximately 15 cases diagnosed in the Czech Republic each year. The recent World Health Organization classification recognizes several histopathological subtypes of medulloblastoma: classical, desmoplastic/ nodular with its extensive-nodularity variant, and anaplastic/ large-cell variant. Further molecular analysis identified four basic subgroups of medulloblastoma: WNT, SHH, Group 3, and Group 4. The subgroup of SHH meduloblastoma is associated with somatic mutations of SHH, PTCH1, SUFU, SMO and TP53, while the most common mutations found in infants up to three years of age were PTCH1 and SUFU. The majority of medulloblastomas are sporadic diseases, whereas only about 5- 10% of all cases occur in connection with hereditary genetic syndromes.

Case: We present a case of a 21-months old girl diagnosed with a localized posterior fossa tumor. The histopathological examination revealed a desmoplastic/ nodular medulloblastoma. The treatment comprised a radical exstirpation of the tumor followed by adjuvant chemotherapy. With the use of array-CGH, a partial biallelic deletion of the SUFU gene (locus 10q24.32) was detected in the tumor DNA, whereas a monoallelic deletion was found in the peripheral lymphocyte DNA of the patient. These findings were confirmed by an independent qPCR method. Monoallelic germline deletion of SUFU was also identified in the patients mother, who was a healthy carrier. Pedigree of the family suggested a transition of the germline deletion of SUFU, since another brain tumors (including one case diagnosed before the age of three years) were identified in previous generations.

Conclusion: Germline mutations in SUFU gene are believed to predispose to infant desmoplastic/ nodular medulloblastomas, basal cell carcinomas and meningiomas. The susceptibility gene shows autosomal dominant inheritance with an incomplete penetrance. There is no evidence-based surveillance strategy suggested for the carriers of germline SUFU mutations/ deletions so far. Our recommendation is based both on a family history of our patient and similar cases described in the literature. Since the germinal mutations in SUFU are responsible for up to 50% of all desmoplastic medulloblastomas in children under three years of age, genetic testing of SUFU should be encouraged in this population of patients.