A 49 year old man suffering from carcinoma of prostate was x -rayed. He showed areas of sclerosis and collapse of T10 and T11 vertebrae in x-ray. The spread of this cancer to the above vertebrae was through

Ans. is 'c' i.e. Internal vertebral plexus of veins Prostatic cancer spreads to the bones through blood vessels; first into the periprostatic venous plexus* and then into the internal vertebral plexus of veins. This metastasis is possible because of valveless communication* between the periprostatic and vertebral plexus of veins.Points of importance -Most common sites * of bony metastasis for prostatic CA-: Lumbar vertebrae > Proximal femur > Pelvis Bony metastasis of prostate CA are mainly osteoblastic* and cause sclerotic lesions.