Nuclear Medicine: A Case-Based Approach Munir Ghesani, Nasrin Ghesani, E Gordon DePuey, Amir Kashefi, Yi Chen Zhang
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Section 1
General Nuclear Medicine
Nasrin Ghesani, Yi Chen Zhang, Munir Ghesani2

3CASE 1: ASSESSMENT OF OSSEOUS METASTATIC DISEASE IN THYROID CANCER

 
Brief History
A 63-year-old female with left leg pain. Plain radiographs showed a lytic bony lesion in the proximal left femur associated with intertrochanteric hip fracture and a soft tissue mass. A whole body bone scan was performed for evaluation of osseous metastatic disease.
 
Findings
Whole body bone scan demonstrates increased tracer uptake corresponding to the pathologic fracture. Uptake on the bone scan in this case may be due to metastatic disease itself, post-traumatic remodeling or a combination thereof. In contrast, significant increased uptake in the left hip on whole body iodine scan is more likely to represent metastatic thyroid carcinoma. Follicular carcinoma is more likely than papillary carcinoma to metastasize to skeleton. Foci of uptake in the neck on the iodine scan may be due to residual thyroid gland after thyroidectomy, local/marginal recurrence of thyroid malignancy or due to regional nodal metastatic disease.
 
Main Teaching Points
  • With regards to skeletal metastatic disease from thyroid carcinoma uptake of radioiodine corresponding to the suspected lesion is more specific for metastatic disease than any uptake on bone scan.
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    Fig. 1: Whole Body Tc-99m methylene diphosphonate (MDP) Bone Scan demonstrated increased radiotracer uptake in the left proximal femur, at the site of known pathological fracture through the known soft tissue mass.
    Follicular carcinoma is 4more likely to metastasize to skeleton whereas papillary carcinoma more commonly spreads to regional lymph nodes in the neck, in the mediastinum and in the lungs.
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    Fig. 2: Whole body 131I scan performed after total thyroidectomy demonstrated increased radiotracer uptake in the thyroidectomy bed, compatible with residual thyroid tissue/residual neoplasm. Markedly abnormal uptake was noted in the left him metastatic lesion.
  • If papillary/follicular tumor dedifferentiates and is no longer ioxdine-avid, but the patient has a rising serum thyroglobulin (Tg), 18F Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) may identify metabolically active tumor.
REFERENCE
  1. Coleman RE. Skeletal complications of malignancy. Cancer. 1997;80(8 Suppl):1588-94.