Pseudoanaplastic tumors of bone

OBJECTIVE

To discuss the concept of pseudoanaplastic tumors of bone, which pathologically show hyperchromatism and marked pleomorphism with quite enlarged, pleomorphic nuclei, but with no to extremely rare, typical mitoses, and to propose guidelines for their diagnosis.

DESIGN AND PATIENTS

From a database of 4,262 bone tumors covering from 1971 to 2001, 15 cases of pseudoanaplastic bone tumors (0.35% of total) were retrieved for clinical, radiographic and pathologic review. Postoperative follow-up after surgical treatment was at least 3 years and a maximum of 7 years.

RESULTS

There were eight male and seven female patients. Their ages ranged from 10 to 64 years with average of 29.7 years. Pathologic diagnoses of pseudoanaplastic variants of benign bone tumors included: osteoblastoma (4 cases), giant cell tumor (4 cases), chondromyxoid fibroma (3 cases), fibrous dysplasia (2 cases), fibrous cortical defect (1 case) and aneurysmal bone cyst (1 case). Radiography of all cases showed features of a benign bone lesion. Six cases, one case each of osteoblastoma, fibrous dysplasia, aneurysmal bone cyst, chondromyxoid fibroma, giant cell tumor and osteoblastoma, were initially misdiagnosed as osteosarcoma. The remaining cases were referred for a second opinion to rule out sarcoma.

CONCLUSIONS

Despite the presence of significant cytologic aberrations, none of our cases showed malignant behavior following simple curettage or removal of bony lesions. Our observation justifies the concept of pseudoanaplasia in some benign bone tumors as in benign soft tissue tumors, especially in their late evolutionary stage when bizarre cytologic alterations strongly mimic a sarcoma.

Epiphyseal osteoblastoma of tibia with xanthomatous stromal reaction

Osteoblastoma occurring in long bones has a distinctive predilection for the metaphysis and the diaphysis. Epiphyseal location is rare. Although variation in histologic patterns is a well-known feature of this tumor, xanthomatous stromal reaction has not yet been described. We report a case of a 34-year-old man who developed an osteoblastoma primarily located in the epiphysis of his left tibia with extension into the metaphysis. The striking histologic features included a prominent xanthoma-like stroma consisting of foamy histiocytes in addition to focal areas with classical configuration of an osteoblastoma. The significance of this finding is discussed.

[Benign osteoblastoma of the frontal sinus]

The extremely rare case of benign osteoblastoma of frontal sinus was presented. Uncharacteristic clinical symptoms, radiological investigations and differentiation diagnostic were analysed. The operation treatment, which was chosen in that case, was described. It was agreeing with treatment presented by the other Polish and foreign authors.

[Is the rings and arcs pattern of mineralization specific for chondroid matrix tumors?]

The rings and arcs pattern of mineralization is considered pathognomonic for cartilaginous tumors. The authors report four cases of osteoblastomas in which the presence of such a pattern of mineralization mistakenly lead to a diagnosis of cartilaginous tumor. These densities are not explained by the histologic findings.

Osteoblastoma as a cause of osteomalacia assessed by bone scan

A 27-year-old female patient was admitted to our hospital with a history of leg pain and mass. She had a benign osteoblastoma in right tibia. Resection of the tumor without treatment by vitamin D antagonist resulted in rapid cure of the osteomalacia. Bone scintigraphy with Tc-99m MDP revealed multiple hot uptakes in initial scan, and follow up scan showed a clear resolution of the lesions.

[Epiphyseal tibial osteoblastoma: report of a rare localization and review of the literature]

Osteoblastoma is an uncommon benign bone tumor diagnosed in about 1% of primary bone tumors. Predominantly observed in the axial skeleton, it can be observed in long bones (20%), generally in the diaphysis (80% of the long bone localizations). In typical cases, standard imaging is highly suggestive of the diagnosis. The typical image is a "lytic" zone surrounded by bony condensation, and a minimal osteosclerotic reaction peripherally, rarely invading the soft tissues. Diagnosis is confirmed at pathology: osteoblast-like cells disseminated in an abundant conjunctive background surrounded by immature richly vascularized bone. The tumor we report presented an unusual localization and an atypical aspect on the imaging studies. Located in the tibial epiphysis, this osteoblastoma invaded the soft tissues, as seen on the CT and MRI studies which visualized an encapsulated tumor with a calcified shell and a liquid-like tumefaction suggestive of a tumor arising from the synovial.

Primary non-odontogenic tumors of the jawbones: an overview of essential radiographic findings

The jawbones, namely the maxilla and mandible, can be the sites of a multitude of neoplastic conditions. Given the variety of processes affecting this particular anatomic area, formulation of a precise diagnosis often can be challenging to the radiologist and the clinician, who may not be familiar with the imaging findings fundamental to diagnosis. Although advanced imaging methods have been developed, routine radiography remains the mainstay in the initial assessment of osseous lesions involving the jawbones. We review and summarize the imaging appearances of non-odontogenic tumors of the jawbones and illustrate example cases of these uncommon neoplasms of bone. Detailed patient history, physical examination, laboratory evaluation and histopathologic analysis are of paramount importance in diagnostic approach and, in most cases, are to be considered in the imaging evaluation of a given lesion. Correct interpretation of the imaging features of lesions involving the jawbones suggests the diagnosis, aids in presurgical planning and improves patient management.

Osteoblastoma of the lumbar spine as a cause of chronic low back pain

We report a case of osteoblastoma in the uncommon location of the L5 lumbar vertebra, detailing the clinical and radiologic aspects. Although the plain radiographs of the patient were normal, computed tomographic scans of the lumbar region confirmed the diagnosis of osteoblastoma or osteoid osteoma of the L5 vertebra. The patient was referred to the orthopedic department for operation. Histologic examination revealed osteoblastoma of the L5 vertebra. Following surgery, the patient's pain resolved completely. Although osteoblastoma is extremely rare in the spine, it should be included in the differential diagnosis as a cause of chronic back pain, especially in young males with painful scoliosis and/or radicular-type leg pain. The tumor is often not readily apparent on plain radiographs. Therefore, advanced radiological investigation is necessary to establish the correct diagnosis.

Osteoblastoma-like osteosarcoma of the distal tibia

We report a case of a 14-year-old boy with an intracompartmental lytic lesion with poorly defined margins in the right distal tibia that was originally treated with curettage and bone grafting. Histologic examination showed an osteoblastic tumor with unusual features, which was found on consultation to be an osteoblastoma-like osteosarcoma, a rare, low-grade variant of osteosarcoma. Subsequently, the patient underwent en bloc resection of the distal tibia, which was replaced with vascularized bone graft and followed by chemotherapy. Two years later, he is alive with lung metastases.

Aggressive osteoblastoma of the mandible closely simulating calcifying epithelial odontogenic tumor. Report of two cases with unusual histopathologic findings

Aggressive osteoblastoma is a rare bone-forming neoplasm composed of prominent epithelioid cells that demonstrate locally invasive growth with a high rate of recurrence but no metastatic potential. Clinical, radiographic and pathologic features of mandibular aggressive osteoblastoma in a 21-year-old African-American male and a 12-year-old Caucasian female are presented. Both tumors were resected with wide surgical margins and neither patient had adjuvant radiation or chemotherapy. The patients showed no evidence of local recurrence or distant spread either clinically or radiographically after two years of follow-up. These tumors were composed of solid sheets of pleomorphic epithelioid cells, eosinophilic amorphous osteoid with foci of calcification, which closely simulated amyloid. Differentiation of this tumor from histologically similar calcifying epithelial odontogenic tumor and low-grade osteosarcoma proved difficult. Immunohistochemical study with osteocalcin confirmed the osteoblastic nature of these epithelioid cells.

[Clinical significance of the increased uptake of a solitary rib lesion in the bone scintigraphy. Based on an osteoblastoma]

A case of a bone tumor located in the right sixth rib detected by means of the bone scan as a solitary lesion is presented. Although the chest X-ray and CT were normal, a low signal intensity on T1 images and high-intensity on T2 images were seen in the MRI. The post-surgical histological diagnosis was osteoblastoma. A review of the clinical significance of solitary rib lesions which appear with increased uptake on bone scan was performed. When a differential diagnosis is made of a solitary rib lesion that appears on a bone scan, osteoblastoma should be considered.

Osteoblastoma of the patella: case report

A 34-year-old man came to our clinic because of left knee pain and mild swelling. Local tenderness over the peripatellar area was observed during physical examination. The range of motion of the knee was full. The radiographic presentation of the patella revealed an osteolytic lesion with a thin sclerotic rim without evidence of extra-articular involvement. The computed tomography revealed an upper pole intraosseous lesion. Intralesional curettage and allogeneic bone grafting were carried out. The pathologic examination demonstrated primitive osteoblasts, with osteoid features and many giant cells. A diagnosis of the osteoblastoma was made. Following surgery, the patient regained full range of motion and was pain-free. Complete healing of the lesion without evidence of recurrence was noted in follow-up radiographs 2 years postoperatively.

Multifocal osteoblastoma of the hand

Osteoblastoma is a benign bone tumor with uncertain radiologic and typical histologic pattern that, in most cases, can be diagnosed without any problems. Usually, it is a solitary bone tumor. The case presented is a 9-year-old child with multiple osteoblastomas occurring in multiple bones of the right hand. The child had pain in his right hand for several weeks. On physical examination, no swelling or other symptoms were elicited. All lesions noted radiologically were treated by curettage, and in all the pattern of osteoblastoma was diagnosed.

Periosteal osteoblastoma: a case report and a review of the literature

Osteoblastomas located on the surface of cortical bone, so-called periosteal (juxtacortical) osteoblastomas, are extremely rare. A 24-year-old man complained of pain and swelling in the left knee. The clinical and radiological investigation showed a tumor located in the posterior portion of the distal shaft of the femur. The radiological differential diagnosis included parosteal osteosarcoma, periosteal chondroma and periostitis ossificans. A frozen section was obtained and histology revealed an osteoblastoma with large epithelioid-appearing osteoblasts consistent with an aggressive osteoblastoma. An en bloc resection of the tumor was performed and the definitive histology of the whole specimen revealed a typical osteoblastoma. The authors draw attention to the fact that periosteal osteoblastoma is a rare tumor that could be mistaken clinically and histologically for other and more common tumors at this location.

Large cell, epithelioid, telangiectatic osteoblastoma: a unique pseudosarcomatous variant of osteoblastoma

A previously undescribed large-cell, epithelioid, and aneurysmal variant of osteoblastoma with minimal osteoid-production--simulating telangiectatic osteosarcoma, epithelioid angiosarcoma, and metastatic carcinoma is reported. The tumor occurred in the mandible of a 14-year-old girl. The light microscopic, immunohistochemical, ultrastructural, cell proliferation, and DNA-ploidy studies, as well as the 7-year disease-free follow-up period all indicate a benign osteoblastic tumor. Cytogenetically, the tumor had a pseudodiploid karyotype, distinguished by a complex t(1;5;17;22) and a terminal 1q deletion. Recognition of this unique, pseudomalignant variant of osteoblastoma is important to avoid an erroneous diagnosis of malignancy.

Recurrent osteoblastoma of the hamate bone. A two-stage reconstruction with a free vascularized iliac crest flap

An osteoblastoma in a carpal bone is very rare and presents a problem of reconstruction after wide tumour excision. We report a case of recurrent osteoblastoma of the right hamate bone with involvement of the ulnar carpal bones and soft tissues that was successfully treated by en bloc resection, temporary interposition of bone cement and fixation with K-wires, followed by reconstruction with a free vascularized iliac crest flap, tailored to the exact size of the defect, in a second procedure. Rapid fusion was achieved and hand function preserved with no evidence of recurrence 3 years postoperatively.

Osteoblastoma in lumbar vertebral body

We report a young man with low back pain suspected to have a disc protrusion. Imaging suggested a tumour of the dorsal portion of the fifth lumbar vertebral body. Operation suggested a giant-cell tumour and subsequent histology showed an osteoblastoma. All typical imaging features of osteoblastoma are demonstrated in this rather uncommon location. Contrast-enhancing bone-marrow oedema on MRI, with mild enhancement of the tumour, together with the CT appearances were the clues to the diagnosis.

Vertebral osteoblastoma: are radiologic structural changes necessary for diagnosis?

BACKGROUND

A case of osteoblastoma localized at the pedicle of the 10th thoracic vertebra is presented.

CASE DESCRIPTION

The patient complained of nocturnal back pain not relieved by salycilates, a typical symptom of osteoblastoma. Bone scintigraphy showed a lower thoracic focus of increased osteoblastic activity; however, X-rays, computed tomography, and magnetic resonance images (MRI) were within normal limits, showing only obscure changes that were also noted in the rest of the spine. Repeat MRI with contrast revealed a focal enhancement. After pediculectomy, histopathologic examination confirmed the diagnosis of osteoblastoma. Fifteen months postoperatively, the patient is symptom-free.

CONCLUSION

Our case demonstrates that some cases of osteoblastoma may not have the classical radiological appearance. Although non-contrast computed tomography and T1-weighted MRI are mildly positive in some instances, osteoblastoma is best visualized on MRI with gadolinium. Like any other neoplasm, osteoblastoma should be detected and removed early, before it can cause structural bony changes.

Spinal osteoblastoma: CT and MR imaging with pathological correlation

OBJECTIVES

To illustrate the CT and MRI features of spinal osteoblastomas and correlate the imaging with histological findings.

DESIGN

In a retrospective review the CT and MRI features of spinal osteoblastomas with respect to mineralisation, signal intensity (SI), adjacent reactive changes, enhancement following gadolinium-DTPA (5 cases) and adjacent soft tissue masses were compared and correlated with the histological findings including the degree of osteoid formation and matrix mineralisation, vascularity and surrounding reactive changes in bone and soft tissue.

PATIENTS

Eleven patients (7 males and 4 females; age range 8-43 years, mean age 19.5 years) with 12 osteoblastomas (1 patient suffered a recurrence) were studied.

RESULTS

All lesions showed classical features on CT with varying degrees of matrix mineralisation, whereas MRI identified mineralisation in only eight of 12 cases. MRI showed low signal intensity of the lesion on both T1- and T2-weighted sequences in several cases in the absence of heavy mineralisation. In these cases, histological examination revealed diffuse osteoid production by the tumour. All patients given gadolinium showed enhancement within the tumour on MRI. Reactive bone marrow changes were identified on MRI in 10 cases, and in five of these the changes were at multiple levels. An adjacent soft tissue mass was demonstrated in five cases, but extraosseous tumour was present histologically in only two of these.

CONCLUSIONS

The MRI appearances of spinal osteoblastomas are varied and show no characteristic features. MRI may also overestimate the extent of the lesion due to extensive reactive changes and adjacent soft tissue masses. CT should continue to be the investigation of choice for the characterisation and local staging of suspected spinal osteoblastomas.

Bone tumors of the coracoid process of the scapula

Bone tumors of the coracoid process of the scapula are rare, and diagnosis and treatment often are delayed. The records of 18 patients with bone tumors of the coracoid process were reviewed. Histologic types included eight cases of ordinary chondrosarcoma, three cases of dedifferentiated chondrosarcoma, two cases of osteoid osteoma, and one case each of osteosarcoma, plasmacytoma, lymphoma, giant cell tumor, and aneurysmal bone cyst. All 18 patients had shoulder pain, and eight of them had been treated with steroid injections for nonneoplastic conditions. Radiologically, chondrosarcoma did not always show clear cortical destruction, and one giant cell tumor had features mimicking those of chondrosarcoma. Five patients (three with dedifferentiated chondrosarcoma, one with chondrosarcoma, one with plasmacytoma) died of disease. The coracoid process was the site with a markedly high proportion of chondrosarcomas. Bone tumors of the coracoid process may be difficult to detect on plain radiographs. In the patient with persistent shoulder pain unresponsive to the selected treatment, additional imaging studies should be considered to eliminate the possibility of a bone lesion.

Acetabular osteoblastoma: description of a case

Osteoblastoma is a slow-progressing, benign bone tumor, that is not frequently observed in clinical orthopaedics (approximately 1% of all primary bone tumors). There is predilection for the vertebrae (posterior arch), the femur, the tibia, and the cranium; it affects young subjects (from 10 to 35 years), with predilection for males (males: females = 2:1). Symptoms are not very specific, characterized essentially by moderate, discontinuous pain, that is responsive to treatment by NSAIDS; it may, at times, be asymptomatic. On radiographic assessment it is viewed as a lytic area that is rounded, greater than 2 cm in size, with unclear margins, with or without peripheral bone reaction. It is not easy to diagnose osteoblastoma, particularly if it is localized in unusual sites, such as in the pelvis. The authors present a case of osteoblastoma of the acetabular bottom in a subject aged 22 years, that was not diagnosed unrecognized for about 2 years from the onset of symptoms.

Osteoblastoma of the foot and ankle

A total of 329 patients with osteoblastoma were retrospectively reviewed from the archives of the Armed Forces Institute of Pathology, of which 41 (12.5%) presented with tumors in the foot and ankle. This was the third most common site of disease after the spine and femur. Overall, the mean age was 22.5 years, which was the same for the foot and ankle subset of patients; however, there was a significant male predominance in foot and ankle patients compared with the whole group. The majority of patients were skeletally mature (85.4%). Clinically, most patients presented with pain (97.2%), although one-third of the total related a history of antecedent trauma. The interval between the onset of symptoms and biopsy was 84 days (range, 0-572 days). Radiographically, the majority of lesions were in the hindfoot (N = 18; 44%) of which 16 of 18 tumors (89%) were in the talus. Of these, one-half were subperiosteal and dorsally based and were associated with osseous tumor matrix and a soft tissue mass. Two osteoblastomas, both in the metatarsals, transitioned into sarcomas; the rest were histologically benign. For diagnostic purposes, it was essential to obtain clinical, radiographic, and histologic correlation.

Osteoid osteoma and osteoblastoma with clonal chromosome changes

We cytogenetically investigated six osteoid osteomas, one osteoblastoma and one aggressive osteoblastoma, and observed clonal structural changes in one osteoid osteoma and in the aggressive osteoblastoma. Clonal chromosome changes had not been reported previously in osteoid osteoma, whereas the only reported chromosome change in osteoblastoma was different from the one presented here.

[Benign osteoblastoma of the hand. A case--review of the literature]

One case of a benign osteoblastoma, localised on the proximal phalanx of right thumb is reported. Three points are emphasized: the low frequency in the hand, only six observations are reported in the English literature, one from Jaffe (1932) and four from Lichtenstein (1964) and one from Mosher and coll (1978). The non-specificity of the signs and X-ray are must consider chondroma, giant cell tumor, chondrosarcoma or aneurysmal cyst. The lesion is benign and so the treatment must be conservative.

Osteoid osteoma and osteoblastoma of the spine. Factors associated with the presence of scoliosis

STUDY DESIGN

A retrospective study of 44 museum cases of spinal osteoid osteoma or osteoblastoma and a meta-analysis using 421 additional cases from a review of the literature.

OBJECTIVES

To identify the factors that are associated with the development of scoliosis in these patients.

SUMMARY OF BACKGROUND DATA

Painful scoliosis is a well recognized presentation of spinal osteoid osteoma and osteoblastoma and is considered to be secondary to pain-provoked muscle spasm on the side of the lesion. Previous studies have been based on small numbers of patients that did not permit statistical validation of the reported observations.

METHODS

Eight factors were assessed including: age, gender, duration of symptoms, site of lesion in the spine, vertebral level of lesion, site of lesion in the individual vertebra, type of lesion, and Cobb angle at presentation. Reports were reviewed only if the presence or absence of scoliosis could be determined. Statistical analyses initially were performed on the museum cases and then on a combination of museum cases and cases from the literature.

RESULTS

Overall, 63% of subjects had scoliosis. The lesions were typically present on the concave aspect of the curve. Three cases of scoliosis from the literature involved lesions that were reported to be on the convexity. Scoliosis is significantly more common in cases of osteoid osteoma than in cases of osteoblastoma (P < 0.0001); lesions are more common in the thoracic and lumbar regions than in the cervical region (P < 0.0001), in lower cervical region than in the upper cervical region (P value = 0.0027), and they are more commonly located to one side of the midline (P < 0.0001). Age, gender, and duration of symptoms were of no significance.

CONCLUSIONS

The findings support the concept that scoliosis is secondary to asymmetric muscle spasm in patients with spinal osteoid osteoma or osteoblastoma.

Disappearance of 99mTc-MDP accumulation in metastatic bone disease during bone scintigraphy

We describe a patient with progressive metastatic bone disease involving a pedicle of the lumbar spine, in whom serial bone scans were performed. Initially, increased radiotracer accumulation was evident, corresponding to an osteoblastic lesion found on CT. Later, radiotracer uptake appeared to be normal, while an expansile tumor causing osteolytic change was noted on CT. We suggest that false-negative bone scan can occur in the natural process of progressive bone metastasis.

[Osteoblastoma: analysis of the treatment of 24 cases]

The authors study 24 patients with the histologic diagnosis of osteoblastoma treated from 1953 to 1996, with a mean follow-up of 33.4 months. Two were considered as a malignant osteoblastoma. Twenty-two cases were operated, and in 2 of these was performed only a selective embolization to pelvic and spine localization. It was discussed clinical and radiographic aspects and the response to treatment. It was obtained 20 good and 4 poor results.

Benign osteoblastoma of the temporal bone

We report a case of benign osteoblastoma arising in the temporal bone of a 28-year-old woman. Plain radiography showed a mass with an amorphous calcified matrix and a thin radiolucent marginal zone. CT and MR imaging were useful in delineating the extent of the tumor, and angiography showed its hypervascularity. Preoperative transarterial embolization was effective in reducing bleeding during surgery.

Unusual imaging findings in association with spinal osteoblastoma

This paper describes four patients with spinal osteoblastoma that had unusual imaging features. Two cases arose in the cervical spine and two in the thoracic spine. Three tumours were associated with diffuse sclerosis of the vertebral body (an 'ivory vertebra'). All of these lesions either arose in the vertebral body or extended into the body from the adjacent pedicle. Reactive sclerosis at multiple levels was seen in three cases (one involving adjacent vertebral bodies, two involving adjacent pedicles or laminae and one involving multiple ribs). Osteophyte formation was identified bridging the disc space on the concave side of a scoliosis in two cases. Another case had an unusual scintigraphic appearance with an area of linear activity adjacent to the tumour. The finding of an 'ivory vertebra' in a child or young adult should raise the possibility of osteoblastoma involving the vertebral body, especially if there is an associated scoliosis.

Osteoblastoma: varied histological presentations with a benign clinical course. An analysis of 55 cases

The presence of epithelioid osteoblasts, lace- or sheet-like osteoid production, and a permeative pattern of tumor growth in osteoblastomas is thought to be associated with an aggressive clinical behaviour. This study assessed the prognostic significance of these and other histologic parameters by analyzing a large group of cases. Histologic material obtained from 55 patients who had osteoblastoma diagnosed and treated at Memorial Sloan-Kettering Cancer Center was analyzed. Additionally, the radiographic images were studied and the lesions were radiologically staged as stage 1 (quiescent), stage 2 (active), or stage 3 (aggressive). Epithelioid osteoblasts were detected in 14% of the cases without any mitotic activity. Lace- or sheet-like osteoid was present in 36% of the cases studied. A permeative pattern of tumor growth was present in 15% of lesions in all but one arising in the short tubular or large flat bones. Thirty-four percent of the lesion were in stage 1, 48% in stage 2, and 17% in stage 3. All stage 1 tumors involved long tubular bones, whereas all stage 3 tumors arose in the short tubular or flat bones. Local recurrence was noted in 16% of patients, all of whom had stage 2 lesions. One patient with a vertebral tumor eventually died with persistent disease. No association between the histologic features and disease outcome was demonstrated. The clinically aggressive behavior of osteoblastoma is not related to particular histologic features, but rather to the skeletal location. Mitotic activity is not present in osteoblasts in the osteoblastoma.

Aggressive osteoblastoma with focal malignant transformation and development of pulmonary metastases. A case report with a review of literature

We report the case of a 57-year-old woman with an unusually fast-growing and destructive osteoblastic tumor affecting the left humeral head. On histopathologic examination, most of the initial tumor revealed the characteristic morphologic features of a benign-appearing aggressive osteoblastoma. Based upon the presence of a few small scattered areas composed of atypical osteoblasts in abundant lace-like osteoid showing vascular permeation, the definitive diagnosis was that of an osteoblastoma with focal malignant transformation to well-differentiated osteosarcoma. Molecular biologic analysis revealed a splice mutation at the exon 5 donor site of the p53 gene, clearly indicating a malignant potential of the tumor. The proximal third of the humerus was resected en bloc and replaced by an uncemented modular endoprosthesis. Five months after surgery, an extensive local soft tissue recurrence occurred. Eight months postoperatively, a further massive recurrent tumor had developed an multiple pulmonary metastases became evident. Chemotherapy caused a marked decrease in the size of the soft tissue recurrences and the lung metastases showed no further increase of their number and size. Osteoblastomas with conversion to osteosarcoma should be considered a separate clinicopathologic tumor entity to be distinguished from genuine osteosarcoma. All cases of malignantly transformed conventional and aggressive osteoblastomas reported to date have shown a conversion to low- or high-grade osteosarcomas only in recurrent tumors. The present case supports the concept that osteoblastomas may primarily undergo early malignant transformation. Osteoblastomas with conversion to osteosarcoma require an aggressive surgical approach followed by chemotherapy in the hope of prolonging life expectancy or obtaining a cure.

CT and MR imaging of vertebral osteoblastoma. A report of two cases

Two patients with spinal osteoblastoma evaluated with computed tomography (CT) and magnetic resonance imaging (MRI) are presented. A brief literature review is added.

CT and MRI of aggressive osteoblastoma of thyroid cartilage

We present a unique case of aggressive osteoblastoma arising from thyroid cartilage. A 52-year-old man presented with a 10 month history of neck discomfort but without frank pain. CT and MR examinations disclosed a well defined mass arising from the thyroid cartilage. This lesion had areas of coarse calcifications and a central area of lucency. The appearance suggested chondrosarcoma. Hemilaryngectomy was performed to remove the mass en bloc. Surgical pathology diagnosed aggressive osteoblastoma arising from thyroid cartilage.

Quantitative analysis of solitary lesions of bone

RATIONALE AND OBJECTIVES

To quantitate the radiographic features of common solitary lesions of bone using vector analysis to optimize their radiographic description.

METHODS

Plain radiographs of 709 solitary bone lesions were reviewed. Relevant demographic, anatomic, and structural data were cataloged. These data were used to approximate the vector space defined by all possible solitary lesions of bone. Vector space analysis on the entire set of lesions was performed to determine similarities among and between lesion types.

RESULTS

The 709 lesions generated 614 separate vectors within the appearance vector space. Only 10 vectors were represented more than 3 times, indicating great variability among and between most lesion types. Osteochondromas (with two vectors repeated 10 and 15 times, respectively) and peripheral chondrosarcomas (with one vector repeated 5 times) were relatively uniform in appearance. Gender bias was present for multiple types of lesions. Larger lesions that involved more than one anatomic center were more likely to be malignant. Lesions occurring in the femoral diaphysis and pelvic flat bones were statistically more likely to be malignant.

CONCLUSIONS

Analysis shows that most lesions have highly varied vectors in the appearances within the vector space. More in-depth analysis of each lesion type using this quantitative technique is required to better define individual lesion subspaces and hence their radiographic appearances with respect to other bone lesions.

[Benign bone tumors in the growth years--osteoid osteoma and osteoblastoma]

Osteoid osteoma (ICD: 9191/0) and osteoblastoma (ICD: 9200/0) are closely related entities of osteoblastic-type tumors. Osteoid osteoma is a small benign (lesion 1-2 cm or less) neoplasm that is richly vascularized. Nerve fibers within the tissue surrounding the nidus lead to the characteristic pain. A typical finding is the perifocal osseous reaction around the nidus. Osteoblastoma is a progressively growing lesion of a diameter larger than 2 cm; it is sometimes painful and is characterized by the absence of any reactive perifocal bone formation. For both tumors the treatment is complete surgical excision. If the nidus of the osteoid osteoma is removed, the patient will be free of pain. For the osteoblastoma the treatment depends on the stage and localization of the tumor. Forty-seven patients with osteoid osteoma and 10 patients with osteoblastoma have been treated in Heidelberg since 1980. The radiological investigations and surgical treatment are discussed.

Benign osteoblastoma of the parietal bone

A 5-year-old girl presented with a 1-year history of a subcutaneous swelling in the right parietal region. There were no cerebral symptoms or signs. Plain X-ray of the skull showed a lytic bony lesion with sclerotic margin. Computed tomography showed a hypodense, osteolytic lesion with thinned and bulged inner and outer skull tables with intact continuity. There was no intracranial lesion. At operation, the mass was found to be pink and granular, and was totally enucleated. Histology revealed it to be a benign osteoblastoma.

Acquired vitamin D-resistant rickets caused by aggressive osteoblastoma in the pelvis: a case report with ten years' follow-up and review of the literature

Rickets or osteomalacia secondary to tumor in either bone or soft tissue is rare and interesting in that it can be cured after removal of the tumor. The majority of the reported cases occurred in adults older than 30 years, and the most commonly associated types were vascular and fibrous tumors. We present a new case of aggressive osteoblastoma in the ilium, which induced vitamin D-resistant rickets in an 8-year, 9-month-old boy. Radiographs and blood chemistry findings on admission showed typical features of active hypophosphatemic ricketts. He underwent three local excisions of the tumor. At 10-year follow-up, the patient was symptom free but short. When a child has symptoms of rickets that develop relatively later than ordinary vitamin D-resistant rickets, every effort should be made to search out a tumorous lesion before attributing it to a renal origin.