Final answer:
Glioblastoma multiforme is the most common primary brain tumor in individuals over 60, characterized by a rapid growth rate and a challenging prognosis.
Step-by-step explanation:
The most common primary brain tumor in patients over 60 years of age is B. Glioblastoma multiforme (GBM). GBM is known for its aggressive nature and poor prognosis. It is a type of tumor that arises from astrocytes, the supportive cells in the brain, and can grow very rapidly. Although treatments such as surgery, radiation, and chemotherapy are available, the survival rate remains low. Unlike several other health issues such as neurocysticercosis, neurotoxoplasmosis, and various types of cancer including pancreatic cancer, breast cancer, and non-Hodgkin's lymphoma, the treatment of GBM is exceptionally challenging due to its location and the difficulty of completely removing or treating the tumor without damaging normal brain tissue.