Mechanism of intramedullary high intensity area on T2-weighted magnetic resonance imaging in osteoid osteoma: a possible role of COX-2 expression

MR Imaging of Osteoid Osteoma: Pearls and Pitfalls

Osteoid osteoma (OO) is a benign bone neoplasm consisting of a central prostaglandin-secreting nidus surrounded by a zone of reactive sclerosis. The diagnosis is suspected in children and young adults with longstanding nighttime pain that is relieved by salicylates or nonsteroidal anti-inflammatory drugs. Early studies suggested that computed tomography had a higher sensitivity and specificity in the diagnosis of OO compared to magnetic resonance imaging (MRI). More recent literature suggests MRI done with dynamic postcontrast imaging to be equal to or slightly better at detecting the nidus of OOs, particularly the ones in atypical locations. Being able to evaluate for OO utilizing MRI is important given that the majority of these lesions occur in younger patients, in whom there is greater concern to limit ionizing radiation. Furthermore, patients with atypical OOs often receive an MRI if radiographs are not suggestive of the diagnosis. Therefore, it is important for radiologists to be aware of the imaging features that can help make the diagnosis on MRI.

Resection of a Rare Metacarpal Distal Condyle Osteoid Osteoma

Introduction

Osteoid osteoma is a benign bone-forming tumor with young male predilection. It occurs predominantly in the long bones. In the hand, osteoid osteoma is more commonly located in the phalanges and carpal bones. The metacarpals are the least common site for osteoid osteoma. Pain is the most common symptom. It usually increases at night and responds to nonsteroidal anti-inflammatory drugs.

Case Presentation

The authors report the excision of an osteoid osteoma lying at the distal condyle of a metacarpal bone of the left hand. The clinical and radiological findings are exposed as well as the surgical management of the lesion. Pain and swelling disappeared after surgery, and there was no evidence of recurrence at follow-up.

Discussion

They discuss this rare location and further radiological examination that was used leading to the diagnosis. The imputation of the traumatic factor has been discussed, along with the different therapeutic possibilities and the advantages of a total excision while preserving the integrity of the adjacent ligament and joint space.

Conclusion

The surgical alternative appears to be a satisfying treatment for osteoid osteoma in this particular superficial location. Both the exact pathogenesis and the contribution of the traumatic factor remain unclear.

Microendoscopic Excision of Osteoid Osteoma in the Pedicle of the Third Lumbar Vertebra

We present a rare case of a patient who underwent complete microendoscopic excision of an osteoid osteoma, which induced radiculopathy without nerve root compression. A 20-year-old man presented severe right groin pain that was temporarily relieved by nonsteroidal anti-inflammatory drugs. A computed tomography (CT) scan showed typical features of a nidus located in the inferior cortex of the right L3 pedicle. We performed surgery using a posterior microendoscopic approach. We drilled vertically along the line of the cortex of the caudal pedicle using a high-speed drill. After identifying the tumor, en bloc resection of the nidus was achieved. Immediately after surgery, pain in the right groin disappeared. A CT scan showed that most of the right L3 pedicle remained. This minimally invasive technique preserves spinal structures, including the facet and pedicle, and is a viable option for the treatment of spinal osteoid osteomas located close to vital structures.

Osteoid osteomas: a pain in the night diagnosis

Osteoid osteoma is a common benign bone-forming lesion that is composed of a nidus of vascular osteoid tissue and woven bone lined by osteoblasts. It is frequently associated with considerable surrounding inflammation. The diagnosis is usually straightforward when imaging reveals a radiolucent nidus surrounded by variable degrees of reactive sclerosis. However, the diagnosis can be elusive when osteoid osteomas occur in atypical locations, as they may have a nonspecific and misleading appearance on different imaging modalities, particularly on MRI. The purpose of this pictorial essay is to review the typical and atypical features of osteoid osteomas on different imaging modalities, and the appearance of osteoid osteomas in different locations. We also review growth disturbances caused by osteoid osteomas and potential mimickers, with imaging characteristics that can aid in diagnosis.

Symptomatic resolution of spinal osteoid osteoma with conservative management: imaging correlation

A 10-year-old girl presented with a history of painful scoliosis. Imaging performed, including computed tomography (CT) and magnetic resonance imaging (MRI), demonstrated a lesion with radiological features consistent with an osteoid osteoma (OO) of the 6th thoracic vertebra. The patient was treated conservatively with non-steroidal anti-inflammatory drugs (NSAIDs). Over eight months of clinical and radiological surveillance, she became entirely asymptomatic and demonstrated complete resolution of the scoliotic curve. The CT and MRI features of the osteoid osteoma during the period of surveillance are presented and are correlated with the corresponding clinical features.

Utility of immunohistochemical analysis for cyclo-oxygenase 2 in the differential diagnosis of osteoblastoma and osteosarcoma

AIMS

To study the immunoexpression of cyclo-oxygenase (COX) 2 in osteoblastomas (OBs) and osteosarcomas (OSs), and to assess the utility of immunohistochemical analysis for COX 2 in the differential diagnosis of the two tumour forms.

METHODS

The immunohistochemical features of COX 2 were studied in 11 OBs and 30 OSs, including 26 high-grade OSs (16 osteoblastic, 7 chondroblastic, and 3 fibroblastic) and 4 low-grade OSs.

RESULTS

Tumour cells from all 11 OBs unequivocally showed diffuse, intense and cytoplasmic immunoreactivity for COX 2. Strong cytoplasmic expression of COX 2 was observed in 5 of 26 (19%) high-grade OSs, all chondroblastic. In one osteoblastic-type OS, COX 2 was expressed in the chondroblastic component, but this tumour was considered to be COX 2 negative. No COX 2 expression was noted in atypical osteoblastic cells. Staining in the four low-grade OSs was negative.

CONCLUSION

The results of immunohistochemical analysis of COX 2 suggest that in addition to the routine histopathological evaluation, COX 2 is a valuable diagnostic marker in the distinction between OB and OS.

Imaging features of spinal osteoid osteoma with emphasis on MRI findings

A retrospective evaluation of the imaging of 13 patients with a diagnosis of osteoid osteoma (OO) of the spine was undertaken. Available imaging included radiographs (n=10), computed tomography (CT) (n=13), bone scintigraphy (n=5) and magnetic resonance imaging (MRI) (n=13). MRI features evaluated were pattern of neural arch and vertebral body oedema and the presence of an identifiable nidus. MRI features were correlated with other available imaging. There were seven males and six females with an age range of 8-59 years. On radiographs, scoliosis was present in ten and a sclerotic pedicle in nine patients. Focal increased uptake on bone scintigraphy consistent with OO was seen in all five patients where scintigraphy was available. On CT, a nidus was identified in all patients and reactive sclerosis was seen in 12. MRI demonstrated the nidus in eight patients and unilateral neural arch oedema with anterior extension to involve the ipsilateral posterolateral vertebral body in 11. When MRI is performed in the evaluation of back pain, the presence of unilateral neural arch oedema extending to involve the posterolateral vertebral body raises the possibility of spinal OO and should prompt CT to confirm the presence of a nidus.

The diagnostic accuracy of MRI versus CT imaging for osteoid osteoma in children

Advanced imaging often is obtained in children suspected of having osteoid osteoma. We hypothesized that magnetic resonance imaging gives a falsely aggressive appearance and that computed tomography is better for identifying osteoid osteoma. This is the first prospective blinded study comparatively assessing these imaging studies in children. Twelve preoperative magnetic resonance imaging scans of confirmed cases of osteoid osteoma were collected. Three radiologists blinded to the diagnosis reviewed these images. Only a clinical history of skeletal pain was given. Lesions were classified as benign-latent, benign-aggressive, or malignant. Radiologists were asked to list their primary diagnosis (with a confidence level from 1-10). Seven of these 12 children also had computed tomography scans that subsequently were reviewed in similar manner. With computed tomography scans, lesions were accurately identified as benign-latent (15/21 readings, 71%) and as osteoid osteoma (14/21 readings) more frequently than with magnetic resonance imaging scans (7/36 readings, 19%).

LEVEL OF EVIDENCE

Diagnostic study, Level III-1 (study of nonconsecutive patients--no consistently applied reference gold standard). See the Guidelines for Authors for a complete description of levels of evidence.

Solid variant of aneurysmal bone cysts in long tubular bones: giant cell reparative granuloma

OBJECTIVE

The purpose of this study was to determine the age distribution, location, and imaging features of histologically proven solid variants of aneurysmal bone cysts in long tubular bones.

MATERIALS AND METHODS

We performed a retrospective review of imaging studies of histologically proven solid aneurysmal bone cysts in long bones between 1961 and 2001. There were 30 cases comprising 29 radiographic, six CT, and eight MR imaging examinations. The lesions were evaluated for bone involved, location within a long bone, matrix, size, soft-tissue mass, and MR imaging characteristics. The imaging findings were correlated with the histologic findings.

RESULTS

The patients were 17 females and 13 males ranging in age from 2 to 58 years (mean, 18 years). The bones involved were the femur (n = 10), the ulna (n = 7), the tibia (n = 7), the humerus (n = 2), the radius (n = 2), and the fibula (n = 2). The lesions were five juxtaarticular, 13 metaphyseal, one diametaphyseal, and 11 diaphyseal. The location was eccentric in 20 cases, of which two were intracortical and two periosteal, and central in 10. Lesion size varied between 1 and 7 cm. Thirty-three percent of lesions were nonaneurysmal. Four lesions were mineralized. A soft-tissue mass was present in four cases. Four lesions showed a permeative-lytic pattern simulating a malignant process. Unusual findings included periosteal reaction and development of a solid aneurysmal bone cyst in a preexisting fracture. MR imaging showed solid elements in all cases and pronounced edema in 50% of cases.

CONCLUSION

Solid aneurysmal bone cyst is a reactive nonneoplastic bone lesion with varied imaging characteristics; one third of lesions are nonaneurysmal.