[Chondromyxoid fibroma].

Chondromyxoid fibroma is a benign chondroid tissue tumor characterized by the lobular overgrowth of stellate or elongated cells in the myxoid or chondroid intracellular matrix. There may be giant multinucleate cells. They may be encountered in any skeletal bones, mainly at the age of 20-30 years. A positive reaction with S-100 protein, d smooth muscle actin, and CD 34 was immunohistochemically detected in chondromyxoid fibroma tissue. In chondromyxoid fibroma, the prognosis is favorable. Recurrence of the tumor is observed in 15% of the surgically treated cases.

TGF-beta1 drives partial myofibroblastic differentiation in chondromyxoid fibroma of bone.

Chondromyxoid fibroma (CMF) is a rare benign cartilaginous bone tumour with a lobular architecture containing stellate and myofibroblast-like spindle cells. The aim of this study was to investigate the presence, spatial distribution, and extent of myoid differentiation in CMF and to evaluate a possible causative role for TGF-beta1 signalling, which is known to promote smooth muscle actin (SMA) expression. Twenty cases were studied for immunoreactivity for muscle-specific actin (MSA), SMA, desmin, h-caldesmon, calponin, TGF-beta1, and plasminogen activator inhibitor type 1 (PAI-1). The extent of myofibroblastic differentiation was further investigated ultrastructurally, including immuno-electron microscopy using antibodies against MSA and SMA, focusing upon the different cell types in CMF. The expression of potential genes driving this process was quantified by Q-RT-PCR (TGF-beta1, fibronectin, its EDA splice variant, and PAI-1). Tumour cells, especially those with a spindled morphology, showed diffuse immunoreactivity for MSA, SMA, TGF-beta1, and PAI-1, while desmin, h-caldesmon, and calponin were absent. Ultrastructurally, neoplastic cells showed the presence of myofilaments and rare dense bodies, which were more prominent in spindle cells and less so in chondroblast-like cells. Immuno-electron microscopy confirmed the actin nature of these myofilaments. No fibronexus was identified. The functional activity of TGF-beta1 was demonstrated by the identification of PAI-1, a related downstream molecule both immunohistochemically as well as by Q-RT-PCR. There was a linear correlation between TGF-beta1 and PAI-1 expression. Fibronectin-EDA levels were low. We have therefore substantiated the presence of morphological, immunohistochemical, and immuno-electron microscopic partial myofibroblastic differentiation in CMF, driven by TGF-beta1 signalling.

Chondromyxoid fibroma: a tumor showing myofibroblastic, myochondroblastic, and chondrocytic differentiation.

Chondromyxoid fibroma (CMF) is a rare primary benign tumor of bone that demonstrates variable histologic features and is often confused with chondrosarcoma. Although the chondroid elements in CMF have been reported to be S-100 protein positive and to have chondrocytic features ultrastructurally, the immunohistochemical and ultrastructural profile of CMF, especially with respect to the peripheral nonchondroid elements, has not been extensively studied. Formalin-fixed, paraffin-embedded tissue from 10 CMFs were stained immunohistochemically with antibodies to vimentin, desmin, muscle actin, smooth muscle actin, S-100 protein, and CD34. Six tumors were also examined ultrastructurally. The chondroid areas showed variable staining for S-100 protein but did not stain for muscle actin or smooth muscle actin. The peripheral areas surrounding the chondroid areas stained diffusely for smooth muscle actin and muscle actin but did not stain for S-100 protein. CD34 highlighted the extensive vascularity that was especially prominent in the peripheral areas; no tumor cells stained for CD34. There was no staining for desmin. Ultrastructural examination showed three different cell types. Some cells showed the classic features of chondrocytes, other cells had the features of myofibroblasts, and the third cell type had the features of both chondrocytes and myofibroblasts ("myochondroblasts"). These findings support the conclusion that CMF is a tumor showing myofibroblastic, myochondroblastic, and chondrocytic differentiation.

A chondromyxoid fibroma-like tumor of the cranial convexity: immunohistochemical and ultrastructural study.

A rare chondromyxoid fibroma-like tumor arising from the temporal bone in a 49-year-old man is described. This case appears to be only the second reported of a cranial lesion of the tumor for which diagnosis could be confirmed by immunohistochemistry and electron microscopy.

Chondromyxoid fibroma of the jaws. Case report and review of the literature.

Chondromyxoid fibroma is a benign tumor of bone that is characterized by chondroid and myxoid differentiation and by ultrastructural and immunohistochemical evidence of chondral origin. It is rare in the jaws and skull bones, where only about 2% of all cases have been reported. A review of the 20 acceptable gnathic cases in the literature and of the current case revealed both a higher incidence in the mandible (76%) than in the maxilla (24%) and an equal sex distribution. The sites of occurrence in both jaws are compatible with origin from developmental cartilaginous remnants. The controversies regarding malignant transformation and therapeutic approach are addressed.

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.

Actin-positive chondroblasts (myochondroblasts) in benign chondroblastoma.

We studied the result of immunostaining for muscle specific actin in 15 chondroblastomas and observed distinct muscle actin positive chondroblasts and chondrocytes in five cases. In their cytoplasm actin positive cells contained bundles of microfilaments with focal densities on the ultrastructural level, but they differed from myofibroblasts in many aspects. Analogously to the terminology of myofibroblasts such cells can be probably designated as myochondroblasts having characteristic immunophenotype (vimentin, S-100 protein, NSE and muscle actin positivity).

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.

Ultrastructural appearance of chondroblastoma.

The ultrastructural appearance of two chondroblastoma were examined by scanning and transmission electron microscopy. The polygonal basal cells, with a scanty pericellular matrix, show a poorly developed endoplasmic reticulum and many Golgi bodies. The highly differentiated chondroid cells are assembled in isogenous clusters and show intracytoplasmic inclusions of glycogen and lipids, numerous mitochondria and superficial secretion vesicles arising from a well developed rough endoplasmic reticulum. Clusters of crystals, in close contact with the matrix collagen fibres are found near to the tumour cells. These ultrastructural characteristics, together with the basal undifferentiated cells that proliferate and differentiate into cartilaginous tissue, distinguish this neoplasm from chondroma, mesenchymal chondrosarcoma and chondromyxoid fibroma and confirm its chondroid origin.

[Clinicopathological analysis, immunohistochemical study and electron microscopic observation of chondroblastoma of bone].

A series of 73 cases of chondroblastoma of bone, a rare benign tumor, was subjected to clinicopathological analysis, 50 cases of it were studied by immunohistochemistry and affinity histochemistry and 3 cases were observed by electron microscopy. In this series, chondroblastomas were found nearly in patients of all age groups, with the peak incidence occurring in the second decade of life. The lesions were more commonly located in long bone metaphyseal portion, especially in the upper end of femur and the head and neck of femur. It was easily misdiagnosed as giant cell tumor of bone, chondroma, and osteochondroma by clinic and radiography. There was gradual transition from a few chondroblasts to a small focus of clear cells in 3 cases, therefore, chondroblastoma may transform into clear cell chondrosarcoma by anaplastic change of chondroblast, which is one of malignant chondroblastomas. Our immunohistochemistry and affinity histochemistry results supported the point of view of chondroblast originated from epiphyseal chondrocytes. Immunohistochemical assessment of S-100 protein may be one useful parameter for differentiating chondroblastoma from giant cell tumor of bone and aneurysmal bone cyst ultrastructurally, chondroblasts had characteristic lobulated nuclei, compact zones under nuclear membrane, and microvilli on cells surface. In most cells, the Golgi apparatus and RER were inconspicuous without.

[Electron microscopic and immunohistochemical studies on chondroblastoma].

Six clinically and patho-histologically proven cases of chondroblastoma were studied with electron microscopic and immunohistochemical methods. The tumor tissues of chondroblastoma exhibited biphasic pattern i.e., chondroid and cellular area. In the chondroid area, small and round tumor cells contained many filaments in the cytoplasm and small processes in the cell wall. Many glycogen granules were present in the tumor cells in some cases. Intercellular matrix was immunohistochemically positive for S-100 protein and showed fine collagen fibers were very similar to those of articular and epiphysial cartilage. Many portions of mitochondria, cell wall and matrix of chondroblastoma tissue clearly exhibited calcification but were not definitely ossification. In the cellular area, tumor cells were composed of small immature mesenchymal and clear large degenerated tumor cells, histiocytes with lysosomes and osteoclast-like multinuclear giant cells. Immunohistochemical studies in the cellular area revealed that there were many tumor cells positive for lysozyme, alpha 1-antitrypsin and alpha 1-antichymotrypsin. In the transitional zone between chondroid and cellular area, degenerated tumor cells were found. The chondroblastoma was composed of chondroid and histiocytic areas which were very similar to those of chondromyxoid fibroma. The present study appears to demonstrate that chondroblastoma originates from a mixture of chondrocytic and histiocytic tumor cells but not from articular and epiphysial cartilage.

Chondroblastoma of the rib presenting as an intrathoracic mass. Report of a case with fine needle aspiration biopsy, immunocytochemistry and electron microscopy.

We describe an unusual case of chondroblastoma of the rib, initially presenting as a mediastinal mass eroding a vertebra, in which the preoperative diagnosis was made by fine needle aspiration (FNA) cytology and confirmed by histology and electron microscopy of the surgical specimen. Cytologic study of the smears revealed osteoclastlike giant cells and dishesive, mononucleate tumor cells; sections of the paraffin-embedded, aspirated material showed the chondroid matrix and typical chicken wire calcific deposits. Supporting diagnostic evidence was provided by immunohistochemical demonstration of S-100 protein. Unusual features were the presence of intranuclear pseudoinclusions and cytoplasmic granular deposits, which proved to contain iron on histochemical staining, ultrastructural morphology and x-ray analysis. This case emphasizes the value of FNA cytology in providing a correct diagnosis of chondroblastoma as well as the utility of embedding the aspirated material for histologic, immunohistochemical and ultrastructural studies.

Chondroblastomalike extraskeletal chondroma.

An unusual extraskeletal tumor occurring in the right thumb of a 44-year-old man exhibited histologically a chondroblastomalike appearance. The tumor was characterized by dense proliferation of chondroblastic cells admixed with a few multinucleated giant cells of osteoclast type. The patient had no evidence of local recurrence or metastasis three-and-a-half years after a simple excision.

[Histogenesis of chondroblastoma--a study of tissue culture, immunohistochemistry and electron microscopy].

Two cases of chondroblastoma were studied by tissue culture, immunohistochemistry and electron microscopy as to the histogenetic origin of the tumor cells in tissue culture, the tumor cells were epithelioid in shape with plenty cytoplasm. They were arranged loosely with marked contact inhibition of growth. The cells in these two cases were able to survive for two months through 5 passages. By immunohistochemical study, the tumor cells showed strongly positive reaction to S-100 protein and lysozyme but negative reaction to alpha-antichymotrypsin. Under electron microscope, the surface of tumor cells possessed many microvilli. The tumor cells were characterized by obvious nuclear multilobulation and pseudoinclusion with marked margination of chromatin. In the cytoplasm, scanty amount of ERE and Golgi apparatus were seen. All the above findings support that chondroblastoma cells are derived from immature cartilage cells analogous to fetal cartilage. Moreover, some huge bizarre tumor cells were observed during the later stage of culture which has not been reported in the literature so far.

Chondroblastoma arising in the triradiate cartilage. Report of two cases with review of the literature.

Chondroblastoma is a relatively rare benign bone tumor of cartilage origin. Roentgenologically it presents usually as a region of lytic destruction of bone with a thin sclerotic rim in the epiphysis of long tubular bone. Less than 9% occur in the pelvic bones but show a tendency to arise from the triradiate cartilage. We present two cases of chondroblastoma originating in the triradiate cartilage, each showing extensive lytic bony destruction and an intrapelvic soft tissue mass. A review of the literature suggests that chondroblastoma of the triradiate cartilage shows an aggressive radiological appearance.

[Ultrastructural characteristics of chondroblastomas]. / Ul'trastrukturnaia kharakteristika khondroblastom.

The ultrastructure of chondroblastomas and two new ultrastructural peculiarities typical of the given form of tumours are described. Being typical but not constant these peculiarities may be an additional argument indicating that such cells may be regarded as chondroblastoma cells. The ultrastructure of these cells is similar to that of normal epiphyseal chondrocytes and differs from the ultrastructure of chondrosarcoma cells.

Ultrastructure of cartilaginous tumors and S-100 protein in the tumors. With reference to the histogenesis of chondroblastoma, chondromyxoid fibroma and mesenchymal chondrosarcoma.

Twelve cartilaginous tumors were studied by electron microscopy and the presence of S-100 protein was studied immunohistochemically in order to clarify the cell origin of chondroblastoma, chondromyxoid fibroma, and mesenchymal chondrosarcoma. Three chondroblastomas were characterized by round or ovoid tumor cells with some cytoplasmic processes, well-developed organelles and thick fibrous laminae in the nuclear membrane, occasional multinucleated giant cells and scanty chondroid matrix. S-100 protein was demonstrated in the tumor cells and some multinucleated giant cells Two chondromyxoid fibromas revealed tumor cells of varied shapes with characteristic cartilaginous differentiation and abundant chondroid matrix. Spindle tumor cells showed the ultrastructural features of cartilage cells rather than of fibroblasts and S-100 protein was also demonstrated in their cytoplasm. Chondroblastoma and chondromyxoid fibroma were considered to arise from chondrocytes. Mesenchymal chondrosarcoma ultrastructurally exhibited round tumor cells with cartilaginous nature in cartilage islands. Poorly-differentiated portions were composed of primitive round or elongated cells with occasionally admixed round cells with ultrastructural features of cartilaginous differentiation. S-100 protein was demonstrated in the cells in cartilage islands and in single cells admixed in poorly-differentiated portions. These results support the hypothesis of primitive mesenchymal origin with a tendency to differentiate toward cartilage cells.