Chondroblastoma of bone. A clinical, radiological, light and immunohistochemical study

Giant Cells of Various Lesions Are Characterised by Different Expression Patterns of HLA-Molecules and Molecules Involved in the Cell Cycle, Bone Metabolism, and Lineage Affiliation: An Immunohistochemical Study with a Review of the Literature

Giant cells (GCs) are thought to originate from the fusion of monocytic lineage cells and arise amid multiple backgrounds. To compare GCs of different origins, we immunohistochemically characterised the GCs of reactive and neoplastic lesions (n = 47). We studied the expression of 15 molecules including HLA class II molecules those relevant to the cell cycle, bone metabolism and lineage affiliation. HLA-DR was detectable in the GCs of sarcoidosis, sarcoid-like lesions, tuberculosis, and foreign body granuloma. Cyclin D1 was expressed by the GCs of neoplastic lesions as well as the GCs of bony callus, fibroid epulis, and brown tumours. While cyclin E was detected in the GCs of all lesions, p16 and p21 showed a heterogeneous expression pattern. RANK was expressed by the GCs of all lesions except sarcoid-like lesions and xanthogranuloma. All GCs were RANK-L-negative, and the GCs of all lesions were osteoprotegerin-positive. Osteonectin was limited to the GCs of chondroblastoma. Osteopontin and TRAP were detected in the GCs of all lesions except xanthogranuloma. RUNX2 was heterogeneously expressed in the reactive and neoplastic cohort. The GCs of all lesions except foreign body granuloma expressed CD68, and all GCs were CD163- and langerin-negative. This profiling points to a functional diversity of GCs despite their similar morphology.

Clinicopathological and Prognostic Characteristics in Spinal Chondroblastomas: A Pooled Analysis of Individual Patient Data From a Single Institute and 27 Studies

STUDY DESIGN

Retrospective pooled analysis of individual patient data.

OBJECTIVES

Spinal chondroblastoma (CB) is a very rare pathology and its clinicopathological and prognostic features remain unclear. Here, we sought to characterize the clinicopathological data of a large spinal CB cohort and determine factors affecting the local recurrence-free survival (LRFS) and overall survival (OS) of patients.

METHODS

Electronic searches using Medline, Embase, Google Scholar and Wanfang databases were performed to identify eligible studies per predefined criteria. A retrospective review was also conducted to include additional patients at our center.

RESULTS

Twenty-seven studies from the literature and 8 patients from our local institute were identified, yielding a total of 61 patients for analysis. Overall, there were no differences in clinicopathological characteristics between the local and literature cohorts, except for absence or presence of spinal canal invasion by tumor on imagings and chicken-wire calcification in tumor tissues. Univariate Kaplan-Meier analysis revealed that previous treatment, preoperative or postoperative neurological deficits, type of tumor resection, secondary aneurysmal bone cyst (ABC), chicken-wire calcification and radiotherapy correlated closely with LRFS, though only type of tumor resection, chicken-wire calcification and radiotherapy were predictive of outcome based on multivariate Cox analysis. Analyzing OS, we found that a history of preoperative treatment, concurrent ABC, chicken-wire calcification, type of tumor resection and adjuvant radiotherapy had a significant association with survival, whereas only type of tumor resection remained statistically significant after adjusting for other covariables.

CONCLUSION

These data may be helpful in prognostic risk stratification and individualized therapy decision making for patients.

Anatomical Reconstruction of the Acromion Using an Autologous Iliac Crest Graft for Treatment of Recurrent Chondroblastoma: A Case Report

CASE

A 38-year-old man presented with recurrent chondroblastoma of the acromion after primary curettage and bone grafting. The patient underwent revision surgery with resection of the acromion and reconstruction using an autologous iliac crest graft. He had regained normal shoulder function without recurrence at a follow-up of 17 months.

CONCLUSIONS

This case demonstrates a rare location of chondroblastoma and successful anatomical and functional reconstruction. The described surgical procedure could be considered for large tumorous lesions of the acromion, for which curettage would be insufficient, and to preserve and reconstruct a functionally intact shoulder girdle.

Chondroblastoma of the patella with pathological fracture in an adolescent: a case report

BACKGROUND

Chondroblastoma is a rare primary bone tumor of young people that generally occurs in the epiphyseal plate of long bones. To date, only 13 cases of patella with pathological fracture in chondroblastoma have been previously published.

CASE PRESENTATION

A 15-year-old male patient presented with acute pain in the left knee after an injury occurred while playing basketball. Plain radiographs and computed tomography showed a pathological fracture of the left patella with an osteolytic lesion (1.5 × 2 × 3 cm). Magnetic resonance imaging revealed an expansile lesion within the patella with a slightly high signal on the T1-weighted image, a high signal on the T2-weighted image and soft tissue swelling in front of the patella. A ^m99Tc bone scintigraphy revealed moderate uptake. The preoperative diagnosis was chondroblastoma. This patient underwent intralesional meticulous extended curettage, adjuvant high-speed burr, 95% alcohol and electrotome treatment, autogenous iliac crest bone grafting, and internal fixation. A postoperative pathological diagnosis was chondroblastoma. The patient's function was satisfactory, and there was no sign of tumor recurrence. The internal fixator was good, with no loosening or migration observed at the last follow-up at 20 months after surgery.

CONCLUSIONS

Rarely, chondroblastoma of the patella can present with acute pain due to pathological fracture. We present the 14th such case in the literature to associate patellar chondroblastoma with pathological fracture. The patient was treated with curettage, inactivation, autogenous bone grafting, and internal fixation. A satisfactory therapeutic effect was obtained. This case may be beneficial to the diagnosis and treatment of chondroblastoma patella.

Selected Giant Cell Rich Lesions of the Temporal Bone

Giant cell rich lesions of the temporal bone encompass a wide spectrum of disease that includes infectious, reactive, and neoplastic processes. When dealing with any lesion that can potentially involve bone, it is important to understand both the clinical presentation and to correlate the histologic findings with the radiologic imaging. This review discusses the clinical, the pathologic features including the differential diagnosis, and the treatment of some of the more commonly encountered giant cell rich entities in this region.

Clinical features, treatments and long-term follow-up outcomes of spinal chondroblastoma: report of 13 clinical cases in a single center

PURPOSE

Chondroblastoma (CB) in the spine is extremely rare and there is little published information regarding this subject. We attempt to explore the clinical features of spinal CB and address the importance of total resection, especially total en bloc spondylectomy (TES) for the treatment of spinal CB.

METHODS

Clinical data of 13 consecutive CB patients who received surgical treatment in our center between January 2006 and December 2016 were reviewed retrospectively. Recurrence-free survival (RFS) was estimated by Kaplan-Meier method and Log-rank test.

RESULTS

The 13 CB patients included 9 men and 4 women with a mean age of 32 years. The lesions were located in the cervical spine in 2 cases, thoracic spine in 5 cases, and lumbar spine in 6 cases. All the patients were treated surgically using either curettage, piecemeal total resection, or TES. Postoperative radiotherapy was administered in 2 cases. The mean follow-up period was 41.6 months. Relapse occurred in 3 (23.1%) cases, resulting in one death in 60 months. The mean RFS duration was 28.7 months.

CONCLUSIONS

CB predominantly affects males and various age groups. Spinal CB more commonly involves the thoracic and lumbar segments. Spinal CB usually appears as an aggressive and destructive bony lesion with a soft tissue mass on imaging, forming compression on the spinal cord in some cases. Recurrence is not uncommon for spinal CB. Total resection, especially TES, has been confirmed as a powerful method to control the disease, while curettage is more likely to associate with local recurrence. Radiotherapy does not seem to reduce local recurrence.

Chondroblastoma of the distal femoral metaphysis: A case report with emphasis on imaging findings and differential diagnosis

Chondroblastoma is a rare benign tumor, consisting of tissue resembling foetal cartilage, and arising in the epiphyses, or apophyses of long tubular bone. However, chondroblastoma of the cortex of the long bone metaphysis is extremely rare.A 15-year-old girl presented a 10-month history of intermittent knee pain and without mobility limitation. X ray, computed tomography (CT), and magnetic resonance imaging (MRI) showed a slightly expansile lytic lesion involving the metaphyseal cortex of the left distal femur. During histological examination, typical features of chondroblastoma were observed. Chondroblastoma was definitely and histologically diagnosed. Surgical procedures included intralesional tumor curettage and allograft bone implantation. The patient was discharged without any complications 1 week after surgery and there was no recurrence during a 10-month follow-up.This report describes a case of chondroblastoma in the metaphyseal cortex of the distal femur and serves as a reminder of the atypical anatomic location of chondroblastoma. Patients in an appropriate age group with typical imaging features may be diagnosed with chondroblastoma despite its rare location.

Chondroblastoma: An Update

Chondroblastoma is a rare primary bone tumor of young people that typically arises in the ends of the long bones. Radiologic investigations show a small, circumscribed, lytic lesion. The tumor is characterized histologically by the proliferation of chondroblasts along with areas of mature cartilage, giant cells, and occasionally, secondary aneurysmal bone cyst formation. Chondroblastoma, however, may also present with atypical features, such as prominent hemosiderin deposition, numerous giant cells, or the presence of a large aneurysmal bone cyst component. Malignant entities such as clear cell chondrosarcoma and chondroblastic osteosarcoma must also be considered. Recently, immunohistochemical stains such as DOG1 and SOX9 have been described in chondroblastoma, and K36M mutations in either the H3F3A or H3F3B genes have also been identified. While generally regarded as a benign entity, chondroblastoma manifests an intermediate type of behavior, given its ability to recur locally, and rarely, metastasize.

Chondroblastoma of the thoracic spine: a rare location. Case report with radiologic-pathologic correlation

Chondroblastoma is a rare benign cartilage neoplasm that arises from the appendicular skeleton in the vast majority of the cases (80%). Chondroblastoma of the spine is an even more rare condition (30 cases reported), and vertebral chondroblastomas, unlike chondroblastomas of the extremities, present with the appearance of an aggressive tumor on CT and MR imaging and occur at least a decade later. Even though vertebral chondroblastomas are very uncommon tumors, they should nonetheless be included in the differential diagnosis when encountered with an aggressive vertebral mass, and a histological confirmation should be performed. We present a case of chondroblastoma of the thoracic spine of a 27-year-old female for which detailed radiologic-pathologic correlation was obtained.

Complete local tumor control after curettage of chondroblastoma-a retrospective analysis

BACKGROUND

Chondroblastoma is an uncommon benign bone tumor with an incidence of 1 to 2% among all primary bone tumors. In the past, treatment for chondroblastoma has been highly variable leading to different rates of recurrences. Therefore we aimed to determine: (1) the rate of recurrence, (2) the complication rate, (3) and functional outcome after intralesional curettage of chondroblastoma.

HYPOTHESES

Intralesional curettage with high speed burring and packing can avoid local recurrences.

PATIENTS AND METHODS

Experiences of 22 patients with chondroblastoma of the bone were retrospectively reviewed. The patient group consisted of 16 men; 6 women; mean age 24years (range; 12-58years) affecting in 15 the lower- (68%) and in seven the upper extremity (32%).

RESULTS

There was no local recurrence or malignant transformation. All patients underwent intralesional curettage, followed by defect filling presenting in 19 patients (87%) excellent clinical and oncological results (mean MSTS 98.9). Complications were seen in two patients. Pain was the main revealing symptom of the chondroblastoma (n=16, 73%). Mean follow-up of all patients was 114months (range, 25 to 480months).

DISCUSSION

Aggressive curettage and packing provided excellent local tumor control and functional results in our patients with chondroblastoma. Malignant transformation is extremely rare, however, present in literature but was not seen in any of our patients.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Metachronous Bilateral Chondroblastoma of the Proximal Part of the Femur with a Pathologic Fracture: A Case Report

CASE

A twenty-two-year-old man presented with metachronous bilateral chondroblastoma of the proximal part of the femur with a pathologic fracture. The pathologic fracture on the right side was treated with tumor resection and total hip arthroplasty. Within forty-three months, the chondroblastoma in the left femoral head was detected and treated with the same protocol as the chondroblastoma on the right side. No metastatic lesion was evident at this time; because of its benign appearance histologically, the lesion was diagnosed as a metachronous lesion.

CONCLUSION

In a patient who has been previously diagnosed with and treated for chondroblastoma, skeletal pain at another site may represent a metachronous lesion.

Free vascularized fibula graft to treat chondroblastoma of the hip

Chondroblastomas are rare tumors that present in the epiphysis of the long bones. Bone grafting following aggressive surgical curettage has yielded the best results. When present in the femoral head, they pose a higher risk of recurrence due to the difficulty of achieving an adequate resection without destroying the structural integrity of the weight-bearing surface. This article describes a case of surgical treatment of a chondroblastoma of the femoral head with the use of a free vascularized fibula graft. A 26-year-old woman had several months of increasing left hip pain and decreased range of motion. Imaging studies confirmed a large bubbly lesion with sclerotic borders in the left femoral head consistent with chondroblastoma. After performing an aggressive and complete excisional biopsy, a large cavitary defect remained in the femoral head. Reconstruction of the defect and structural support was achieved using a free vascularized fibula. Nine years postoperatively, the patient had full hip motion, no pain, and no radiographic evidence of collapse. A free vascularized fibula graft is an excellent option for the reconstruction of a large femoral head defect after chondroblastoma resection.

Discovered on gastrointestinal stromal tumour 1 (DOG1): a useful immunohistochemical marker for diagnosing chondroblastoma

AIMS

  Cellular areas of chondroblastoma are composed of polygonal chondroblasts with indented nuclei and scattered osteoclast-type multinucleated cells. To learn more about the phenotype of chondroblasts, we investigated the expression of several established immunohistochemical markers in chondroblastomas.

METHODS AND RESULTS

  Nine chondroblastomas were analysed using immunohistochemical antibodies [CD34, α-smooth muscle actin (α-SMA), DOG1, CD117, AE1/AE3 and CD163]. Ten chondromyxoid fibromas, seven giant cell tumours of bone and four foetal proximal femurs were also analysed. The cellular areas of each chondroblastoma contained nests of DOG1(+) αSMA(+) CD117(-) CD34(-) chondroblasts, a phenotype that was not detected in chondromyxoid fibroma cases or in giant cell tumours. Although AE1/AE3 was expressed in all chondroblastomas, the staining intensity and proportion of the positive cells varied widely. Intra-lesional CD163(+) macrophages were detected in all cases of chondroblastoma, chondromyxoid fibroma and giant cell tumours.

CONCLUSIONS

  Our results demonstrated nests of membranous DOG1(+) chondroblasts located within cellular portions of chondroblastoma containing diffuse heterogeneous infiltrates of mostly DOG1(-) chondroblasts, CD163(+) macrophages and multinucleated osteoclastic giant cells. Thus, chondroblastoma can be added to the tumours that are usually positive for DOG1, alongside gastrointestinal stromal tumour (GIST), rare solid-pseudopapillary neoplasms of the pancreas and exceptional mesenchymal tumours including uterine type retroperitoneal leiomyoma, peritoneal leiomyomatosis and synovial sarcoma.

Chondroblastome métaphyso-diaphysaire du fémur

Chondroblastoma is a rare benign tumor of cartilage tissue accounting for less than 1% of all bone tumors. The epiphysis of long bones is the typical localization, often extending to the metaphysis. Metaphyseal, metaphysodiaphyseal or pure diaphyseal forms are exceptional. We report a case in a 15-year-old boy who presented a metaphyso-diaphyseal chondroblastoma of the distal portion of the left femur. The inaugural signs were pain and limited joint motion. We discuss the anatomic aspects and the clinical course of this rare tumor and present current knowledge of the histogenesis.

The application of immunohistochemistry in the diagnosis of bone tumors and tumor-like lesions

Immunohistochemistry (IHC) plays an important role in the diagnosis of some bone tumors, especially in the differential diagnosis of primary from metastatic non-osseous tumors and in the categorization of small-round-blue-cell tumors. This article reviews immunomarkers used in bone tumors and their diagnostic significance.

Chondroblastoma of the lumbar spine. Report of two cases and review of the literature

Chondroblastoma is a benign cartilaginous neoplasm that generally affects the appendicular skeleton. Twenty-six cases of spinal chondroblastoma have been reported in the past 50 years, only six of which were located in the lumbar region. The authors report two cases involving this exceptional location. In both patients, low-back pain, in the absence of radicular pain, was the presenting symptom. In both cases, plain radiography and computerized tomography scanning revealed an osteolytic lesion surrounded by marginal sclerosis. Magnetic resonance imaging allowed the authors to study the tumor's local extension. Examination of a percutaneous fluoroscopy-guided biopsy sample revealed the following typical histological features of chondroblastoma: chondroid tissue, focally alternating with cellular areas, and no nuclear atypia or pleomorphism. To reduce the risk of local recurrence, vertebrectomy and anterior-posterior fusion were performed in both cases. In one case, a structural lumbar scoliosis was corrected during the posterior procedure. There was no postoperative complication. No recurrence was observed during the 3- to 6-year follow-up period. The surgery-related results were deemed successful. Although exceptional, the diagnosis of chondroblastoma is possible in lesions involving the lumbar spine. Other spinal locations are described in the literature, and frequency of recurrence is stressed. A vertebrectomy is advised to reduce the risk of local recurrence.

Receptor activator of NF-kappaB ligand (RANKL) is expressed in chondroblastoma: possible involvement in osteoclastic giant cell recruitment

AIMS

Chondroblastoma is a rare, locally aggressive bone tumour that causes osteolytic destruction at the epiphyseal end of the affected bone. It is possible that tumour cells may stimulate osteoclastogenesis and osteolytic destruction through the production of receptor activator of NF-kappaB ligand (RANKL), which is a key molecule essential for regulating osteoclast formation and activity. Therefore, the expression of RANKL at both the mRNA and the protein level was investigated in chondroblastoma tumour tissue obtained from patients.

METHODS

The expression of RANKL gene transcripts was analysed by the reverse transcription-polymerase chain reaction (RT-PCR), and the cellular localisation of RANKL mRNA and protein was demonstrated by means of in situ hybridisation and immunohistochemistry.

RESULTS

RT-PCR analysis indicated that RANKL mRNA was present in all chondroblastoma specimens and normal cancellous bone samples, but not in normal articular cartilage and chondrosarcoma tissues. In contrast, gene transcripts of osteoprotegerin (OPG), the decoy receptor of RANKL, were detected in all types of tissues. The chondroid origin of neoplastic mononuclear cells in chondroblastoma was confirmed by positive S-100 immunohistochemical staining. Both RANKL mRNA and protein were exclusively expressed in these neoplastic mononuclear cells.

CONCLUSIONS

These findings suggest that RANKL may be involved in the tumour cell induced recruitment of osteoclast-like cells and consequent osteolytic bone destruction in chondroblastoma.

Chondroblastoma: a study of 11 cases

AIM

Chondroblastoma is an infrequent and unique neoplasm that is histologically characterized by chondroblastoma cells, osteoclast-like giant cells and sometimes reactive osteoid. Although it is generally regarded as benign, it may recur and sporadically metastasize to the lung. Many important questions concerning the prognostic factors and adequate surgical treatment of chondroblastoma have not been fully answered and remain controversial. The purpose of this study was to determine clinicopathological features useful in prediction of the tumour behaviours.

METHODS

Eleven chondroblastoma cases were reviwed clinicopathologically. According to Enneking's radiographic grading system, seven cases were classified as stage I, three cases as stage II and one case was classified as stage III.

RESULTS

Nine cases had initially been treated with simple curettage, one had aggressive curettage applied as a primary surgery and one underwent amputation. Among the nine simple curettage cases, one recurred and was reoperated with aggressive curettage. Adjuvant treatment (alcohol and/or cement) was applied in the two aggressive curettage cases; none demonstrated further tumour recurrence. All lesions were curettaged, and one case recurred. The rate of proliferating-cell nuclear antigen expression was significantly higher in the recurrent case.

CONCLUSION

The recurrent case seemed to have a high growth activity. Simple curettage was effective for local control during the initial treatment in most cases, but aggressive curettage and adjuvant treatment with alcohol and/or cement was useful for local control in recurrent chondroblastoma and chondroblastoma presenting with an aggressive behaviour.

Primary treatment of chondroblastoma with percutaneous radio-frequency heat ablation: report of three cases

Chondroblastomas are benign cartilaginous lesions; however, intervention is necessary to stop progression and alleviate pain. The authors evaluated three patients in whom minimally invasive percutaneous radio-frequency heat ablation was used to treat pathologically proven chondroblastoma to determine whether this treatment demonstrated long-term success. The authors found that this approach may be an effective alternative to surgical intervention in some cases.

Chondroblastoma-like chondroma of soft tissue: an underrecognized variant and its differential diagnosis

Soft-tissue chondromas are usually composed entirely of mature hyaline cartilage. Infrequently, however, they may exhibit morphologic features that result in diagnostic difficulty. The authors report a series of eight hypercellular soft-tissue chondromas composed of enlarged chondrocytes within a variable amount of chondroid matrix that often demonstrated delicate calcifications and contained numerous osteoclast-like multinucleated giant cells. This histologic appearance closely resembles that of chondroblastoma of bone. However, its extraosseous location, dense cellularity, and poorly formed cartilage can cause confusion with more aggressive chondroid neoplasms of soft tissue. The clinicopathologic features of these chondroblastoma-like chondromas are discussed, emphasizing the characteristics that facilitate their accurate identification.

Loss of type VI collagen in experimental and most spontaneous human fibrosarcomas

Expression of type VI collagen, an adhesive protein of mesenchymal tissues, is significantly down-regulated upon viral transformation of fibroblasts. Likewise, most cell lines derived from spontaneous mesenchymal tumors, including fibrosarcomas, rhabdomyosarcomas, leiomyosarcomas, chondrosarcomas and liposarcomas, do not synthesize type VI collagen because they are not capable of expressing all 3 of the polypeptide chains required for the assembly of a functional heterotrimeric molecule. When injected into nude mice, neither fibrosarcoma cells (HT1080) nor rhabdomyosarcoma cells (A204) initiate the synthesis of type VI collagen, suggesting that the inhibition is not caused by deficiency of a paracrine factor. Immuno-histochemical studies further illustrate that 15 of 17 spontaneous adult fibrosarcomas lack type VI collagen in the tumor stroma. The absence of this important adhesion protein may contribute to tumorigenicity, invasiveness and/or metastasis of mesenchymal tumor cells.

Chondroblastoma is an osteoid-forming, but not cartilage-forming neoplasm

Chondroblastoma is defined as a 'benign tumour, characterized by highly cellular and relatively undifferentiated tissue composed of rounded or polygonal chondroblast-like cells' and the 'presence of cartilaginous intercellular matrix' (WHO). An extensive analysis of the extracellular matrix composition and gene expression pattern of a large series of chondroblastoma cases shows, however, that type II collagen, which is the main component of any cartilage matrix, is not expressed by the neoplastic cells of this tumour entity and is not deposited into the extracellular tumour matrix. Instead, osteoid and fibrous matrix is formed, with its typical biochemical composition. The multifocal expression of aggrecan proteoglycan in most chondroblastomas explains the bluish, pseudo-chondroid appearance of some of the matrix-rich areas of chondroblastomas. This study did not show chondroid matrix formation or chondroblastic cell differentiation in chondroblastomas, suggesting that chondroblastoma should be classified as a specific bone-forming, rather than cartilage-forming neoplasm.

Muscle-specific actin expression in chondroblastomas

Chondroblastomas are unusual cartilage benign lesions of bone that have well-characterized histological features. We reviewed and immunohistochemically examined the paraffin block material of 20 cases, and in seven tumors of this collection we found distinct cytoplasmic muscle-specific actin positivity of some tumor chondroblasts and chondrocytes. Muscle-specific actin-positive cells had the histological and ultrastructural features typical of chondroblasts. Moreover, in their cytoplasm they contained bundles of microfilaments with focal densities, as is typical of myofilaments. We did not observe any basal lamina around these cells, which were surrounded by intercellular matrix of the cartilage tissue type. Therefore, we suppose that muscle-specific actin-positive cells occurring in some chondroblastomas do not represent an admixture of myofibroblasts but chondroblasts with actin expression. The unusual immunophenotype of some chondroblasts might be the result of aberrant actin expression or of the plasticity of their phenotype modulated by microenvironmental stimuli. It is a question of whether, analogously to the terminology of myofibroblasts, such cells could be designated as myochondroblasts.

Differentiation and proliferative activity in benign and malignant cartilage tumors of bone

To assess the histological grade in benign and malignant cartilage tumors of bone by more objective methods, we examined the differentiation and proliferative activity of tumor cells in six enchondromas, five chondroblastomas, and 13 chondrosarcomas immunohistochemically. A variable number of cells in all tumors showed S-100 protein and vimentin immunoreactivity. In fully differentiated cartilage of enchondromas and low grade chondrosarcomas, tenascin, which is an extracellular matrix glycoprotein, was present in small amounts or absent but was increased at the periphery of tumor lobules and even in the matrix throughout the high grade chondrosarcomas. Higher rate and intensity of proliferating cell nuclear antigen (PCNA) reactivity were found in chondrosarcomas, especially in spindle-shaped cells of high grade tumors, than in enchondromas. The distribution of PCNA-positive cells almost corresponded to the regions with tenascin reactivity. One tumor of high grade chondrosarcoma showed p53 protein immunoreactivity. Aberrant expression of cytokeratin was observed in four chondroblastomas. The expression of desmin was identified in relatively large proportions of enchondromas and chondrosarcomas, regardless of their benign or malignant nature and histological grade. Smooth muscle or muscle-specific actins also were present in a smaller number of tumors. Based on these findings, it is concluded that unusual staining characteristics were present, in addition to those of a chondroblastic nature, in the cartilage tumors of bone. Tenascin and PCNA positivity of various degrees in all chondroblastomas may suggest that they are chondrogenic tumors having a relatively high proliferative activity, albeit their benign clinical course. Proliferative activity of tumor cells in enchondromas and chondrosarcomas correlated well with their histological grade. Tenascin may play a role in promoting tumor cell proliferation of cartilagenous neoplasms and, on the other hand, the alterations of extracellular matrix involving tenascin synthesis seem to be a result of tumor development.

Ultrastructural cytochemical demonstration of proteoglycans and calcium in the extracellular matrix of chondroblastomas

To clarify the characteristics of the extracellular matrix of chondroblastomas, six cases were studied under the electron microscope, with special reference to proteoglycans and calcium in the cellular areas. In ruthenium hexammine trichloride (RHT)-stained sections the matrix was observed to be composed of rounded or polygonal fine granules and unbanded thin filaments that appeared to link neighboring granules together. Treatment with potassium-pyroantimonate showed intracellular accumulation of precipitates, mainly localized within the cisternae of the rough endoplasmic reticulum as well as in the extracellular matrix. The presence of calcium in the precipitates was confirmed using x-ray energy dispersive analysis. These findings, similar to characteristic features observed in calcifying systems, support the theory that chondroblastomas are of chondrogenic origin.