The classic rosette with tumor cells around a central lumen can be seen.In the past, medulloblastoma was classified using histology, but recent integrated genomic studies have revealed that medulloblastoma is composed of four distinct molecular and clinical variants termed WNT/β-catenin, Sonic Hedgehog, Group 3, and Group 4. Of these subgroups, WNT patients have an excellent prognosis and group 3 patients have a poor prognosis. Also, a subgroup-specific alternative splicing further confirms the existence of distinct subgroups and highlights the transcriptional heterogeneity between subgroups. Amplification of the Sonic Hedgehog pathway is the best characterized subgroup, with 25% of human tumors having mutations in Patched, Sufu (Suppressor of Fused Homolog), Smoothened, or other genes in this pathway. Medulloblastomas are also seen in Gorlin syndrome as well as Turcot syndrome. Recurrent mutations in the genes CTNNB1, PTCH1, MLL2, SMARCA4, DDX3X, CTDNEP1, KDM6A, and TBR1 were identified in individuals with medulloblastoma. Additional pathways disrupted in some medulloblastomas include MYC, Notch, BMP, and TGF-β signaling pathways. Diagnosis
The tumor is distinctive on T1- and T2-weighted MRI with heterogeneous enhancement and a typical location adjacent to and extension into the fourth ventricle. Histologically, the tumor is solid, pink-gray in color, and is well circumscribed. The tumor is very cellular, with high mitotic activity, little cytoplasm, and a tendency to form clusters and rosettes. The Chang staging system can be used in making the diagnosis [1]. Correct diagnosis of medulloblastoma may require ruling out atypical teratoid rhabdoid tumor. Treatment
Treatment begins with maximal surgical removal of the tumor.
Dens evaginatus is a rare odontogenic developmental anomaly that is found in teeth where the outer surface appears to form an extra bump or cusp. Premolars are more likely to be affected than any other tooth. It could occur unilaterally or bilaterally. Dens evaginatus (DE) typically occurs bilaterally and symmetrically. This may be seen more frequently in Asians (including Chinese, Malay, Thai, Japanese, Filipino and Indian populations).The prevalence of DE ranges from 0.06% to 7.7% depending on the race. It is more common in men than in women, more frequent in the mandibular teeth than the maxillary teeth. Patients with Ellis-van Creveld syndrome, incontinentia pigmenti achromians, Mohr syndrome, Rubinstein-Taybi syndrome and Sturge Weber syndrome are at a higher risk of having DE. Signs and symptoms
It is important to diagnose DE early and provide appropriate treatment to help prevent periodontal disease, caries, pulpal complications and malocclusion. It occurs on the cingulum/occlusal surface of the teeth. The extra cusp can cause occlusal interference, displace of the affected tooth and/or opposing teeth, irritates the tongue when speaking and eating and decay the developmental grooves. Temporomandibular joint pain could be experienced secondarily due to occlusal trauma caused by the tubercle.This cusp could be worn away or fractured easily. In 70% of the cases, the fine pulpal extension were exposed which can lead to infection, pulpal necrosis and periapical pathosis. Associated anomalies
Additional tubercules
Aesthetic and/or occlusion problems
Agenesis
Bifid cingula
Exaggerated cusp of Carabelli
Gemination
Impaction
Labial drifting
Labial groove
Mesiodens
Megadont
Odontoma
Peg-shaped lateral incisor
Prominent marginal ridge
Shallow groove in the lateral incisor
Shovel-shaped incisor
Supernumerary

Cause
The cause of DE is still unclear.