The diagnosis of solitary primary reticulum cell sarcoma of the posterior fossa with computed tomography.

The CT findings in two surgically and histologically verified cases of primary reticulum cell sarcoma of the cerebellar hemisphere with secondary involvement of the cerebellopontine angle are presented. It is suggested that a correct diagnosis is possible by CT if the following criteria are present: 1. slightly increased attenuation of the mass on the precontrast scan; 2. mottled appearance of the definitely enhancing mass; 3. ill-defined borders on both the pre- and postcontrast scans; 4. degree of mass effect less than that expected from the size of the lesion; 5. involvement of the cerebellopontine angle without signs indicating an extra-axial origin of the tumor. These criteria reflect the gross and microscopic neuropathological features of the tumor.