Cystosarcoma phyllodes of the prostate is a rare, relatively benign sa
rcoma of the prostate. We describe the magnetic resonance imaging find
ings in an unusual case of cystosarcoma phyllodes which resulted in ex
tensive local recurrence and sarcomatous degeneration. Although uncomm
on, radiologists should be aware of the existence of cystosarcoma phyl
lodes of the prostate.