Visualization of nonvascular cranial tumor in cerebral flow study: case report.

Unusual results were obtained from a cerebral blood flow study and a brain scan performed on a patient with an uncommon, nonvascular scalp tumor eventually identified as a proliferating trichilemmal cyst with acanthosis. The tumor accumulated the radionuclide during the early phase of the cerebral flow study, and the increased radioactivity was persistent, being prominently observable in a scan made 3 min and 2 hr after the radionuclide injection. This unusual, positive finding in a cerebral blood flow study of a nonvascular tumor was thought to be a consequence of the higher counting efficiency resulting from the lack of shielding by the skull and from the larger volume of the tumor tissue.