Dad, 85, shallow mid & lower back pain wks ago, pain almost resolved from meds by orth.dr.no other symp. whole spine mri : t2 hyperintense signal noted in spinal cord at the level of d4-d5 intervertebral disc extending for a segment of 10 mm. cancer?

Diagnosing Cancer requires a complete workup including blood, imaging, biopsies, symptom history and examination. Have your dad talk to their Dr who ordered the test to review the results in conjunction with all the other workup components. It is not possible to diagnose Cancer based on stand alone results from an MRI.

Urge you discuss results of study with your personal physician and the involved radiologist, as they know your Dad best, and can correlate results. The T2 lesion is likely chronic, and perhaps secondary to a mild myelomalacia associated with prior trauma or mild cord compression. Seriously, doubt "cancer".