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.