Answer for BIR CoW 26 Sep 2021
Osteoblastoma
Findings
Expansile osteolytic lesion measuring 2.7 x 2.1 cm noted in left pedicle and lamina of C7 vertebra causing partial erosion of left foramen transversarium. Soft tissue thickening noted involving the adjoining scalenus anterior, medius and posterior paraspinal muscles showing enhancement on contrast. Distance between the anterior border of lesion and posterior border of left vertebral artery is 6mm. Prominent twig (small artery) supplying the lesion arising from the left subclavian artery just distal to the origin of left vertebral artery. Right V1,V2 ,V3 and V4 segments of vertebral artery appears hypoplastic starting at its origin from right subclavian artery. Left vertebral artery appears displaced anteriorly due to the osteolytic expansile lesion within left pedicle and lamina of C7 vertebra. No evidence of any abnormal vessel wall thickening , aneuryms,occlusions and stenosis in the visualized blood vessels. Impression: Known case of osteoblastoma C7 vertebra with supply from a small branch of left subclavian artery distal to origin of left vertebral artery causing partial erosion of left foramen tranversarium with surrounding edematous scalenus anterior, medius and posterior paraspinal muscles. HPE - Osteoblastoma
Discussion
Osteoblastomas are primary bone neoplasms with a predilection for the spine. Histologically, they are generally indistinguishable from their smaller counterparts, osteoid osteomas. Osteoblastomas are generally greater than 2 cm in diameter, whereas osteoid osteomas are 1.5 cm or less. Osteoblastomas tend to predominate in the pediatric population during the 2nd decade of life. Osteoblastomas in the spine are typically found in the posterior elements, predominating in the pedicle and lamina. Osteoblastomas, unlike most other primary osseous tumors, typically arise in the spine. Some authors have reported equal frequency of these tumors in the cervical, thoracic, and lumbar spine. Others have reported the cervical and lumbar spine to be the predominant spinal segments involved, followed by the thoracic region and sacrum. On plain radiographs, osteoblastomas are typically radiolucent. They can have variable features, though. One pattern of representation is similar to osteoid osteomas, with a radiolucent nidus and surrounding sclerotic changes. A CT scan may reveal calcification and mineralization of the nidus. Another pattern, which is the most commonly seen, involves an expansile lesion with a multitude of small calcifications and a prominently sclerotic rim . The most aggressive variant displays an expansile pattern, with matrix calcifications, cortical bone destruction, and paravertebral and epidural extension. These more aggressive types of osteoblastomas may radiographically mimic aneurysmal bone cysts, osteosarcomas, or bone metastases. Technetium-99 bone scanning reveals avid uptake at the site of the lesion. Bone scintigraphy is the most sensitive radiographic scan for osteoblastomas. They display an intermediate to low signal on T1-weighted MRI, whereas T2-weighted MRI depicts an intermediate to high signal. A variable enhancement pattern has been noted on MRI. The reactive area surrounding the osteoblastoma often enhances on MRI, which may confound the interpreted boundaries of the lesion.11 A “flare phenomenon” has been described in spinal osteoblastomas. These osseous tumors have the potential to cause a diffuse reactive inflammatory response within adjacent vertebrae, surrounding paraspinal soft tissues, and ribs within proximity. Adjacent bone remodeling at the level of the articular facet may present as facet hypertrophy. This may be a secondary inflammatory reaction to the osteoblastoma. Total excision of an osteoblastoma has been shown to have a more favorable outcome than subtotal excision (curettage) combined with radiation therapy. Osteoblastomas of the cervical spine may lie close to the foramen transversarium, or even encompass the vertebral artery (VA) itself .This poses the potential for significant morbidity if the VA is violated during the course of resection. In such cases in which the tumor is abutting a critical structure such as the VA, it may be a wise decision to perform an intralesional excision, as opposed to the ideally used marginal resection, so as to avoid unnecessary morbidity. An alternative option is to cautiously mobilize the VA if possible, prior to excision of the osteoblastoma. Utilization of advanced technologies such as intraoperative navigation and/or CT scanning may assist in a safer resection of the osteoblastoma.
Findings
Expansile osteolytic lesion measuring 2.7 x 2.1 cm noted in left pedicle and lamina of C7 vertebra causing partial erosion of left foramen transversarium. Soft tissue thickening noted involving the adjoining scalenus anterior, medius and posterior paraspinal muscles showing enhancement on contrast. Distance between the anterior border of lesion and posterior border of left vertebral artery is 6mm. Prominent twig (small artery) supplying the lesion arising from the left subclavian artery just distal to the origin of left vertebral artery. Right V1,V2 ,V3 and V4 segments of vertebral artery appears hypoplastic starting at its origin from right subclavian artery. Left vertebral artery appears displaced anteriorly due to the osteolytic expansile lesion within left pedicle and lamina of C7 vertebra. No evidence of any abnormal vessel wall thickening , aneuryms,occlusions and stenosis in the visualized blood vessels. Impression: Known case of osteoblastoma C7 vertebra with supply from a small branch of left subclavian artery distal to origin of left vertebral artery causing partial erosion of left foramen tranversarium with surrounding edematous scalenus anterior, medius and posterior paraspinal muscles. HPE - Osteoblastoma
Discussion
Osteoblastomas are primary bone neoplasms with a predilection for the spine. Histologically, they are generally indistinguishable from their smaller counterparts, osteoid osteomas. Osteoblastomas are generally greater than 2 cm in diameter, whereas osteoid osteomas are 1.5 cm or less. Osteoblastomas tend to predominate in the pediatric population during the 2nd decade of life. Osteoblastomas in the spine are typically found in the posterior elements, predominating in the pedicle and lamina. Osteoblastomas, unlike most other primary osseous tumors, typically arise in the spine. Some authors have reported equal frequency of these tumors in the cervical, thoracic, and lumbar spine. Others have reported the cervical and lumbar spine to be the predominant spinal segments involved, followed by the thoracic region and sacrum. On plain radiographs, osteoblastomas are typically radiolucent. They can have variable features, though. One pattern of representation is similar to osteoid osteomas, with a radiolucent nidus and surrounding sclerotic changes. A CT scan may reveal calcification and mineralization of the nidus. Another pattern, which is the most commonly seen, involves an expansile lesion with a multitude of small calcifications and a prominently sclerotic rim . The most aggressive variant displays an expansile pattern, with matrix calcifications, cortical bone destruction, and paravertebral and epidural extension. These more aggressive types of osteoblastomas may radiographically mimic aneurysmal bone cysts, osteosarcomas, or bone metastases. Technetium-99 bone scanning reveals avid uptake at the site of the lesion. Bone scintigraphy is the most sensitive radiographic scan for osteoblastomas. They display an intermediate to low signal on T1-weighted MRI, whereas T2-weighted MRI depicts an intermediate to high signal. A variable enhancement pattern has been noted on MRI. The reactive area surrounding the osteoblastoma often enhances on MRI, which may confound the interpreted boundaries of the lesion.11 A “flare phenomenon” has been described in spinal osteoblastomas. These osseous tumors have the potential to cause a diffuse reactive inflammatory response within adjacent vertebrae, surrounding paraspinal soft tissues, and ribs within proximity. Adjacent bone remodeling at the level of the articular facet may present as facet hypertrophy. This may be a secondary inflammatory reaction to the osteoblastoma. Total excision of an osteoblastoma has been shown to have a more favorable outcome than subtotal excision (curettage) combined with radiation therapy. Osteoblastomas of the cervical spine may lie close to the foramen transversarium, or even encompass the vertebral artery (VA) itself .This poses the potential for significant morbidity if the VA is violated during the course of resection. In such cases in which the tumor is abutting a critical structure such as the VA, it may be a wise decision to perform an intralesional excision, as opposed to the ideally used marginal resection, so as to avoid unnecessary morbidity. An alternative option is to cautiously mobilize the VA if possible, prior to excision of the osteoblastoma. Utilization of advanced technologies such as intraoperative navigation and/or CT scanning may assist in a safer resection of the osteoblastoma.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!