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Age / Sex : 67 / F
67/F
C.C.: right pelvic pain for 3 months (Click to enlarge)
1) What is your impression?
2) A first impression and three or less differential diagnoses are acceptable.
Courtesy : Gyung Kyu Lee, MD
Hallym University College of Medicine, Hangang Sacred Heart Hospital
Diagnosis: metastasis from thyroid cancer
Discussion
Findings:
1) AP radiograph of the pelvis shows an expansile, lytic lesion involving medial aspect of right iliac wing with loss of medial cortical margin and extension across right sacroiliac joint. The lesion appears to have no internal matrix mineralization and no periosteal reaction.
2) Bone scan shows decreased tracer uptake in right ilium consistent with lytic lesion seen on plain film
3) Axial and coronal T1-weighted spin-echo MR images of the pelvis show a large, destructive lesion of the right iliac bone with an associated soft tissue mass and extension across right sacroiliac joint to involve the sacral bone. Corresponding axial T2-weighted fast spin-echo MR images shows a high signal intensity mass with a central necrotic portion. Gadolinium-enhanced axial and coronal T1-weighted spin-echo MR images obtained with fat saturation show the homogenous enhancement of the mass with a central necrotic portion. Right iliac bone biopsy showed metastatic thyroid carcinoma
Differential Diagnosis:
Metastasis (extremely aggressive or purely osteolytic lesion),
solitary myeloma (plasmacytoma)
Discussion:
Although most metastatic lesions are multiple, as many as 10% may be solitary. This more commonly occurs with carcinoma of the lung, kidney and thyroid. Specific characteristics of the solitary lesion, such as a bubbly, highly expansile appearance , may suggest a renal or thyroid malignancy.This lesion is characteristically quite large and has been called the blow-out metastatic pattern. A solitary myeloma (plasmacytoma) or giant cell tumor may often give a very similar appearance. Hematogenous dissemination of thyroid carcinoma to the skeleton result in solitary or multiple osteolytic lesions predominating in the axial skeleton. An expansile nature, small calcific collections, a pathologic fracture, and a tendency to extend across joints are some features of thyroid metastases. 99mTc MDP bone scanning is extremely effective in screening for skeletal metastases. Uptake of tracer is dependent on blood flow and on osteoblastic activity. In searching for metastatic disease, it is important not only to delineate the areas of increased activity but also to look for cold lesions, which are usually much more difficult to identify. In cancer patients, focal photon deficient lesions are due to metastatic disease in more than 80% of the cases. They may occur if the tumor is extremely aggressive or purely osteolytic lesion, if there is disruption of the blood supply to the bone, or if there is significant marrow involvement, particularly in a vertebral body. These include highly aggressive anaplastic tumors, reticulum cell sarcoma, renal cell carcinoma, thyroid carcinoma, histiocytosis, neuroblastoma, and especially multiple myeloma.
References:
1. Resnick D. Diagnosis of bone and joint disorders, 4th ed. Philadelphia: Saunders, 2002;4274-4352 2. Yochum TR, Rowe LJ. Essentials of skeletal radiology, 3rd ed. Baltimore: Williams & Wilkins 2005;1137-1167 3. Mettler FA Jr, Guiberteau MJ. Essentials of Nuclear Medicine Imaging, 5th ed. Saunders, 2006;247-254 The copyright of the images remains with the original supplier.
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