Case Author(s): Gabriel De Simon, M.D. and Tom R. Miller, M.D., Ph.D. , 12/19/00. . Rating: #D2, #Q4
Young child with decreased use of the left arm.
Anterior and posterior scintigrams of the calvarium and upper thorax.
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Anterior and posterior scintigrams of the thorax and arms.
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Antero-posterior radiograph of the left shoulder.
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Anterior view of the proximal left humerus with abduction of the left arm.
Full history/Diagnosis is available below
Three year-old boy who has lived the majority of his life in New Guinea. His mother noticed reluctance of the child to use his left arm.
4.4 mCi Technetium 99m MDP i.v.
WHOLE BODY BONE SCINTIGRAPHY:
Focal region of intensely increased activity in the proximal left humeral metaphysis.
Normal distribution of activity in the remainder of the skeleton.
PLAIN RADIOGRAPHS OF THE PROXIMAL LEFT HUMERUS:
Eccentric two centimeter oval lytic lesion, with surrounding, well defined, narrow margin of transition. There is associated lateral metaphyseal periosteal reaction, with no distinct soft tissue component.
Osteoblastoma is a solitary, benign tumor producing osteoid and bone, with 90% of cases reported in the second and third decades of life. Cases have however been reported in patients aged 3-72 years, this patient being at the lower end of this range. There is a male predominance of 2:1. Clinical symptoms often differ from those of osteoid osteoma, with osteoblastoma producing an inconsistent, dull localized pain, as opposed to the intense nocturnal pain caused by osteoid osteoma. Osteoblastoma of the spine accounts for 30-40% of all osteoblastomas, most frequently involving the posterior vertebral elements(55%), although extension into the vertebral body is common(42%). Approximately 60-70% of osteoblastomas occur in the metaphyses and diaphyses of long bones, and rarely in the pelvis. Histological examination reveals features similar to osteoid osteomas, with interconnecting trabecular bone and fibrovascular stroma. An aneurysmal cystic component is seen in 10-15%, and a subgroup appearing similar to osteosarcomas with prominent epithelioid osteoblasts(aggressive osteoblastomas), have also been described.
The bone scintigram performed demonstrates the classical marked radionuclide increased uptake seen with these tumors, but is a non-specific finding. MR imaging is also generally non-specific, with low to intermediate signal intensity on T1 weighted images, and high signal on T2 weighted images. Surgical resection by curettage, intralesional or en-block resection are treatment options. Cryosurgery, radiation and chemotherapy may have a role in aggressive and surgically unresectable lesions of the spine. The recurrence rate for conventional lesions is 10-15%, but aggressive osteoblastomas have a far higher recurrence rate(50%), and rarely transform to osteoblastoma or even metastasize.
The patient underwent an intra-lesional curettage with excision fragments demonstrating nidus formation with islands of osteoid and bone trabeculae lined by osteoblasts, consistent with an osteoblastoma. The patient is presently asymptomatic, and a more extensive en bloc resection of the lesion bed is planned.
Major teaching point(s):
1. Non specific scintigraphic appearance of osteoblastomas, with characteristically intense radionuclide uptake.
2. Usefulness of bone scintigraphy in exclusion of multifocal osseous pathology.
Differential Diagnosis List
1. Osteoid osteoma (excluded on radiographic size).
2. Giant cell tumor.
3. Aneurysmal bone cyst.
4. Fibrous dysplasia.
ACR Codes and Keywords:
References and General Discussion of Bone Scintigraphy (Anatomic field:Skeletal System, Category:Neoplasm, Neoplastic-like condition)
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Case number: bs124
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