Glioblastoma IDH wild-type (multifocal)


The patient went on to have a craniotomy and debulking. 



All the sections show features of a densely cellular astrocytic tumor. The tumor cells have pleomorphic and hyperchromatic nuclei. Many mitotic figures are identified. There are prominent foci of microvascular proliferation. Areas of palisaded necrosis are present.

The tumor cells extend extensively into the cerebral cortex. There is no oligodendroglial component. The features are those of glioblastoma. The tumor cells are focally p53 positive. There is weak staining in 10% of the tumor cells for MGMT immunostain. IDH-1 is negative.

DIAGNOSIS: Glioblastoma (WHO Grade IV).

Note: Although this is tumor is entirely consistent with IDH wild-type molecular subtype, strictly speaking, to conclusively establish this, IDH would need to be sequenced to ensure that a non-IDH1 R132H mutation was present. In practice, an IDH1 R132H negative tumor in an individual over 55-years-of-age makes the possibility of this being IDH mutant remote (<1%), and sequencing is not felt to be necessary by many institutions, and not recommended by the WHO classification of CNS tumors (2016). 

Multicentric vs multifocal

Multifocal glioblastoma is that where multiple areas of enhancement are connected to each other by abnormal white matter signal, which represents microscopic spread to tumor cells. 

Multicentric glioblastoma on the the other hand is where no such connection can be seen. 


In this case, although definite connection cannot be seen, the areas of enhancement are along large connecting white matter tracts and thus almost certainly represent multifocal disease rather than the much rarer multicentric disease.