Pelvic tumor
Pelvic tumors are dangerous because they grow in closed and small spaces that contain important organs that fulfill many different functions. The growing tumor compresses all the surrounding structures, including the sciatic nerve, which passes through the pelvis. As mentioned before, when the nerve is compressed, it will lead to pain, numbness or tingling sensation, which constitutes the classical presentation of sciatica. If the pain worsens or the functions of both urinary bladder or rectum are changed or somewhat affected, that may be a symptom for severe nerve damage which needs doctor intervention.