Tumor in chest bone- is it cancerous?

My father is having a lump on chest bone from past one year and he feels it is increasing in size and feels pains occasionally. Its hard and doesn't move. Nuclear Bone scan says -Osteoblastic lesion on found in sternum near the sterno- costal junction and no other significant osteoblastic lesion in rest of the skeleton. Diabetic- fasting:151 & pp:256. S. Ceratine:1.60mg/dl , alp:61u/L, vit D:12.4 ng/ml, crp -2.30 mg/L. Hiv 1&2,HBsAG, anti HCV, VLDR(Rpr)-Non reactive. Haematology- all values are under normal range. Local orthopedic says reports don't suggest any cancer and doesn't prescribe Biopsy due to high sugar level. I want to know its there any change of tumor being cancerous? Is Biopsy needed? If not what other test can confirm that the tumor is not cancerous? What can be reason for the osteoblastsic lession To develop? Please answer as soon as possible as my entire family is worried.