Medulloblastoma with extensive nodularity

Medulloblastoma with extensive nodularity (MBEN) is a rare variant of medulloblastoma, a malignant brain tumor arising in the cerebellum (the part of the brain located at the back of the skull that controls balance and coordination). MBEN is classified under the desmoplastic/nodular group of medulloblastomas by the World Health Organization (WHO) and is characterized by greatly expanded lobular, reticulin-free zones (nodules) with internodular regions that are markedly reduced. This variant predominantly affects infants and very young children, typically presenting before the age of 3 years. It is associated with the Sonic Hedgehog (SHH) molecular signaling pathway. Clinical features of MBEN include signs and symptoms of a posterior fossa mass, such as headaches, vomiting (often in the morning), unsteady gait (ataxia), poor coordination, and signs of increased intracranial pressure including bulging fontanelle in infants. Hydrocephalus (accumulation of cerebrospinal fluid in the brain) is common due to obstruction of normal fluid pathways. Infants may present with increasing head circumference, irritability, lethargy, and developmental regression. MBEN is generally considered to carry a more favorable prognosis compared to other medulloblastoma variants, particularly in infants. Treatment typically involves maximal safe surgical resection of the tumor. Due to the young age of most affected patients and the desire to avoid the severe neurocognitive effects of cranial radiation on the developing brain, chemotherapy-based strategies are often employed as the primary adjuvant treatment, with radiation therapy reserved or deferred when possible. The relatively good prognosis of MBEN has led to ongoing clinical trials investigating reduced-intensity treatment approaches to minimize long-term side effects while maintaining excellent survival outcomes.

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