Background: Hepatocellular carcinoma (HCC) is the 5th leading cancer which metastasizes to bones in 3%-20% cases. The routes of metastasis from HCC include hematogenous, lymphatic, or direct invasion/dissemination/ seedlings into the surrounding cavities. The 99mTc-methylene diphosphonate (MDP) bone scintigraphy is a sensitive imaging technique for early detection of skeletal metastasis.
Methods: Bone scans of 220 patients with HCC from 1st January 2012 to 31st December 2017, referred to nuclear medicine department for evaluation of skeletal metastasis, were analyzed. About 70% presented with backache followed by rib cage pains (25%).
Results: Out of total 220 patients, 40 patients (18%) had skeletal metastasis on 99mTc-MDP bone scans, with solitary to multiple metastasis ratio was 1:9. Vertebrae were the most common site of metastasis (27/40 patients, 67%). Most striking characteristic of bone metastasis of HCC was the presence of soft tissue element in vertebral metastasis. This soft tissue element is responsible for compression symptoms in these patients. These soft tissue components were poorly outlined on routine planner bone scans due to poor99mTc-MDP uptake but were better diagnosed with Single Photon Emission Tomography / Computed Tomography.‑
Conclusion: Skeletal metastatic distribution of HCC follows an unusual pattern on 99mTc-MDP bone scan with a unique feature of soft tissue component, especially in larger lesions involving spine. During radiotherapy planning, these soft tissue lesions must be included in the field of irradiation to improve post radiotherapy outcome and may play a vital role in determining progression or regression of the disease.
Key words: Hepatocellular carcinoma (HCC), Bone metastasis, Soft tissue component, 99mTc-methylene diphosphonate (MDP) bone scintigraphy, 99mTc-MDP SPECT/CT.
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