Cystosarcoma phyllodes. Report of an unusual case, with death due to intraneural extension to the central nervous system.

Cystosarcoma phyllodes tumors of the breast occasionally exhibit malignant behavior, including chest wall invasion, hematogenous spread or, rarely, metastasis by lymphatic routes. An unusual case of cystosarcoma is presented in which death was apparently caused by perineural and intraneural extension of the tumor along intercostal nerves, to the sympathetic chain, and then to the brain stem by spinal roots, with no evidence of embolic metastasis.