A lump on the middle of the lower spine could be symptomatic of osteomyelitis (a bone infection usually accompanied by pain and inflammation), an abscess (if the lump is on the skin as opposed to the actual vertebra beneath), a bone spur (additional bone growth leading to pain) or a spinal tumor, according to WebMD. Spinal tumors are caused by excessive cell-growth and, while they can often be benign, should be checked by a medical professional.
The precise location of a spinal tumor is often a good indication of its seriousness. Those on the spinal column itself are the most common type of spinal tumor and are often indicative of cancer having spread from elsewhere in the body. The source for this kind of tumor is typically the lungs, breast or prostate, but sometimes also the kidneys, thyroid or gastrointestinal tract. It may also have metastasized from melanoma, lymphoma or sarcoma cancers.
Spinal tumors, whether indicative of cancer or not, are usually accompanied by middle or lower back pain, which might spread to the limbs. This pain might also be resistant to pain-relieving medications.
Other symptoms to be aware of include physical weakness, mobility problems, incontinence, paralysis and spinal deformation.
Since spinal tumors can be life-threatening, it is advised to seek medical attention immediately. Treatment might include surgical or non-surgical procedures.