More recent studies suggest that astrocytes, oligodendrocyte progenitor cells, and neural stem cells could all serve as the cell of origin.Glioblastomas are characterized by the presence of small areas of necrotizing tissue that are surrounded by anaplastic cells. This characteristic, as well as the presence of hyperplastic blood vessels, differentiates the tumor from grade 3 astrocytomas, which do not have these features.GBMs usually form in the cerebral white matter, grow quickly, and can become very large before producing symptoms. Fewer than 10% form more slowly following degeneration of low-grade astrocytoma or anaplastic astrocytoma. These are called secondary GBMs and are more common in younger patients (mean age 45 versus 62 years). The tumor may extend into the meninges or ventricular wall, leading to high protein content in the cerebrospinal fluid (CSF) (> 100 mg/dl), as well as an occasional pleocytosis of 10 to 100 cells, mostly lymphocytes. Malignant cells carried in the CSF may spread (rarely) to the spinal cord or cause meningeal gliomatosis. However, metastasis of GBM beyond the central nervous system is extremely unusual. About 50% of GBMs occupy more than one lobe of a hemisphere or are bilateral. Tumors of this type usually arise from the cerebrum and may exhibit the classic infiltration across the corpus callosum, producing a butterfly (bilateral) glioma. Glioblastoma classification
Brain tumor classification has been traditionally based on histopathology at macroscopic level, measured in hematoxylin-eosin sections. The World Health Organization published the first standard classification in 1979 and has been doing so since.
Persistent polyclonal B-cell lymphocytosis (PPBL) is an anomaly of the human immune system characterized by mildly elevated levels of white blood cells (called leukocytosis), chronic, stable absolute polyclonal B-cell lymphocytosis, elevated polyclonal IgM and binucleated cells. Although cases of non-smoking women or men have been reported, patients are predominantly young smoking women. Signs and symptoms
Ten percent of patients present with splenomegaly and lymphadenopathy. Some patients report a varying degree of fatigue, consistent with a chronic fatigue syndrome, or postviral fatigue as seen in EBV infections while others remain asymptomatic. Genetics
Genetically, PPBL has been associated with a few unusual genetic characteristics. Among them, it is associated with a particular genetic variant of the human leukocyte antigen called HLA-DR7. This variant is normally present in 26% in the Caucasian population. Chromosome analysis has detected an isochromosome +i(3q), with or without premature chromosome condensation. Also, a t(14;18)(q22;21) bcl-2/IgH rearrangement has been described, as usually seen in follicular lymphoma. Immunologically, peripheral B-cells show more functional IgD+ positive CD27 cells than usual. Prognosis
In the followup of 111 patients, most remained stable and event free. However, two patients developed IgM gammopathy 2 lung cancer; one developed cervical cancer and three developed non-Hodgkins lymphoma. The possibility of developing  a clonal proliferation, malignant lymphoma or secondary solid cancer led the authors to conclude not to classify  PPBL as a benign pathology, as has been previously postulated but rather to recommend a careful and continued clinical and biological longterm follow-up. == References ==