Aim: In the present study we examine the role of bone scan with 99mTc-MIBI, following a positive 99mTc-MDP scan, in the work up to differentiate between malignant and benign bone lesions.

Material and methods: Fifty-nine patients, with a positive 99mTc-MDP bone scan had further investigation of the affected area with the oncophilic radiopharmaceutical 99mTc-MIBI (15 mCi). The agent was administered IV and images were obtained (planar/SPECT) 20 min and 3 hours later. All patients had biopsy and CT/MRI imaging.

The 99m Tc-MIBI images were estimated by 3 independent observers and every abnormal uptake, ranging from faint to intense, was considered positive.

Results: 32 patients had benign bone lesions according to histology pathology; 28 of them (87.5%) had a negative 99mTc-MIBI scan (trauma, benign bone tumors). Four patients with benign bone lesions had positive 99mTc-MIBI (chronic osteomyelitis,osteochondroma, osteochondroblastoma, chondroblastoma). 27 patients had malignant bone tumors proven by biopsy; 25 of them (92.6%) had possitive 99mTc-MIBI scans (sarcomas and metastases) and 2 negative (chondrosarcoma, MFH).

Conclusions: The 99mTc-MIBI scan in patients with positive 99mTc-MDP scan and a high index of suspicion for malignancy (either primary or metastatic) was found to have a high negative pedictive value (NPV=0.875) in excluding the presence of malignancy and a high positive pedictive value (PPV=0.926) in identifying patients with malignancy. The 99mTc-MIBI was positive in all patients with metastatic disease (PPV=1.00). We suggest the use of 99mTc-MIBI as a useful method in decision-making in cases with bone pathology.