Findings: Initial chest x-ray demonstrates a right posterior fifth lytic expansile rib lesion. Subsequent CT chest confirms this lytic lesion as well as a mass in the left inferior aspect of the left thyroid. Subsequent ultrasound evaluation confirms the solid nature of the thyroid mass and biopsy confirmed thyroid carcinoma.
Diagnosis: Thyroid carcinoma with skeletal metastases.
Discussion: Thyroid carcinoma has an incidence of 12,000 new cases per year in the United States. The age incidence is usually less than 30 years affecting males greater than females. There is an increased incidence of thyroid carcinoma in patients with a history of neck radiation.
Incidentally detected, nonpalpable thyroid nodules can be problematic. Ultrasound studies reveal approximately 35 to 41% of patients have sonographically identifiable thyroid nodules without clinical evidence of disease. Only a small minority of patients with thyroid nodules have thyroid carcinoma, 90% of these are papillary in histology.
When there are skeletal metastases, these result in either solitary or multiple osteolytic lesions affecting predominantly the actual skeleton. An expansile nature, small calcific collections, a pathologic fracture and a tendency to extend across joints are some features of thyroid metastases. Frequently these are associated with a soft tissue mass.
Another form of cancer that has a similar appearance when it metastasizes to bone is kidney.
References:
Abbitt PL. Ultrasound, A Pattern Approach.
McGraw & Hill, Inc., New York; 1995:449.
Dahnert W. Radiology Review Manual, 3rd Edition.
Williams & Wilkins, Baltimore; 1996: 83.
Resnick D. Bone and Joint Imaging, 2nd Edition.
W. B. Saunders, Co., Philadelphia; 1996: 1085.
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