Human Osteogenic Sarcoma: Fine Structure of the Fibroblastic Type

The fine structure of representative regions of nine fibroblastic osteogenic sarcomas was studied. As judged by light microscopic criteria, the tumors represented both highly malignant (grades 3-4) and less malignant (grade 2) varieties. By electron microscopy, six basic cell types were found in the selected regions (fibroblastlike, histiocytelike, and myofibroblastlike cells, along with xanthoma cells, multinucleated giant cells, and undifferentiated cells). In addition, occasional osteoblastlike cells were encountered. Fibroblastlike cells in general, and especially in grade 2 tumors, showed a fine structure, enabling differentiation from osteoblastlike cells. Multinucleated giant cells were of two morphologic types, and the fine structure appeared to be related to the malignancy potential and differentiation of the tumors. Many muitinucleated giant ceils in grade 2 tumors had a ruffled border and appeared to be highly active in digestive events (especially phagocytosis of whole cells and portions of cells). Accumulation of variable amounts of lipid in droplet form was common in the various types of cells present in the tissues. The observations were discussed with particular emphasis on the interrelationships and functional roles of the cells.     

Human Osteogenic Sarcoma: Fine Structural Localization of Adenosine Triphosphatase

The localization of ATPases in 7 osteogenic sarcomas of osteoblastic, chondroblastic and fibroblastic type was investigated at the fine structural level using two types of substrates: one with lead as capturing ion and one with strontium (the latter presumed to reveal sites of Na⁺-K⁺-dependent transport ATPase).

Reaction product with the lead-ATP medium was located on the plasma membrane and the membranes bordering subjacent vesicles and vacuoles in all the various types of osteoblastlike and fibroblastlike cells and also in types 1 and 3 chon-droblastlike cells, and multinucleated giant cells believed to be neoplastic. Furthermore, deposits of reaction product were demonstrated in lysosome-like organelles in all the aforementioned cells. Except in the case of chondroblastlike cells, precipitates marking the localization of enzyme were confined to areas of the plasma membrane where adjacent cells were closely applied (the free surface lacked precipitates). In chondroblastlike cells the reaction product was usually deposited along the whole plasma membrane. Presence of L-Homoarginine or L-Tetramisole in the incubation medium in concentrations that have been shown to completely abolish alkaline phosphatase activity did not affect the occurrence of the reaction product with ATP as substrate indicating that the enzyme hydrolysing ATP was substrate-specific.

Reaction product marking sites of Na⁺-K⁺-dependent ATPase was confined to plasma membranes and lysosomes of cells in vessel walls.

The observations strengthen the notion obtained in studies on the localization of alkaline phosphatase, namely that osteoblastlike, chondroblastlike, and fibroblastlike cells in osteogenic sarcomas are histogenetically related to one another and to those multinucleated giant cells that presumably are of a neoplastic nature.     

Human Osteogenic Sarcoma: Fine Structural Localization of Adenosine Triphosphatase

The localization of ATPases in 7 osteogenic sarcomas of osteoblastic, chondroblastic and fibroblastic type was investigated at the fine structural level using two types of substrates: one with lead as capturing ion and one with strontium (the latter presumed to reveal sites of Na⁺-K⁺-dependent transport ATPase).

Reaction product with the lead-ATP medium was located on the plasma membrane and the membranes bordering subjacent vesicles and vacuoles in all the various types of osteoblastlike and fibroblastlike cells and also in types 1 and 3 chon-droblastlike cells, and multinucleated giant cells believed to be neoplastic. Furthermore, deposits of reaction product were demonstrated in lysosome-like organelles in all the aforementioned cells. Except in the case of chondroblastlike cells, precipitates marking the localization of enzyme were confined to areas of the plasma membrane where adjacent cells were closely applied (the free surface lacked precipitates). In chondroblastlike cells the reaction product was usually deposited along the whole plasma membrane. Presence of L-Homoarginine or L-Tetramisole in the incubation medium in concentrations that have been shown to completely abolish alkaline phosphatase activity did not affect the occurrence of the reaction product with ATP as substrate indicating that the enzyme hydrolysing ATP was substrate-specific.

Reaction product marking sites of Na⁺-K⁺-dependent ATPase was confined to plasma membranes and lysosomes of cells in vessel walls.

The observations strengthen the notion obtained in studies on the localization of alkaline phosphatase, namely that osteoblastlike, chondroblastlike, and fibroblastlike cells in osteogenic sarcomas are histogenetically related to one another and to those multinucleated giant cells that presumably are of a neoplastic nature.     

Human Osteogenic Sarcoma: Fine Structure of the Osteoblastic Type

The fine structure of representative regions of 13 osteoblastic osteogenic sarcomas was studied. These regions contained four morphologically distinguishable subtypes of osteoblastlike cells. In addition, fibroblastlike and chondroblastlike cells were present, along with multinucleated giant cells, leukocytes, macrophagelike cells, and small populations of histogenetically unclassifiable (but probably neoplastic) cells.

The morphologic evidence was compatible with the view that the variations in appearance among the subgroups of osteobl astlike cells reflected differences in maturation and differentiation of these cells. In at least one subgroup, the morphologic findings suggested that the ceils were capable of manufacturing a secretory product. The multinucleated giant cells occurring in genuine tumor areas appeared to be closely related to neoplastic osteoblasts.

The presence of chondroblastlike cells in the tissues illustrates that cells with a diverging differentiation can occur in an osteoblast-dominated cell population. This agrees with the view that the neoplastic cells originate from a mesenchymal stem cell with potential for multifaceted differentiation.     

Human Osteogenic Sarcoma: Fine Structural Localization of Alkaline Phosphatase

The localization of alkaline phosphatase in eight osteogenic sarcomas of osteoblastic, chondroblastic, and fibroblastic type was investigated at the fine structural level using β-glycerophosphate as substrate and lead as capturing ion. Final product marking localization of alkaline phosphatase was deposited over plasma membranes and associated subplasmalemmal vesicles and vacuoles in various types of osteoblastlike, chondroblastlike, and fibroblastlike cells as well as certain multinucleated giant cells. Presence of L-homoarginine or L-tetramisole in the incubation medium, and incubation at 65°C, prevented the deposition of final product, suggesting that the enzyme studied was “bone specific.” The evidence obtained was compatible with the notion that the different cells showing presence of reaction product were functionally and histogenetically closely related and all were likely to be capable of bone production.     

Osteogenic Sarcoma with Epithelial Differentiation

This case report details an osteogenic sarcoma arising in a vertebra in which cytokeratin intermediate filaments were detected immunohistochemically with three different antibodies. This feature was present not only in the primary neoplasm but also in two local recurrences and a metastasis to the iliac bone. What is unique about this primary bone tumor, however, is the structural evidence for epithelial differentiation. Ultrastructurally, wellformed desmosomes and tonofilaments were present in all four surgically resected specimens. This tumor expands the list of soft tissue and bone tumors in which anomalous expression of intermediate filaments can occur but, more important, illustrates that changes in genetic expression of neoplasia of mesenchymal origin can result in paradoxic epithelial differentiation.     

Osteogenic Sarcoma with Epithelial Differentiation

This case report details an osteogenic sarcoma arising in a vertebra in which cytokeratin intermediate filaments were detected immunohistochemically with three different antibodies. This feature was present not only in the primary neoplasm but also in two local recurrences and a metastasis to the iliac bone. What is unique about this primary bone tumor, however, is the structural evidence for epithelial differentiation. Ultrastructurally, wellformed desmosomes and tonofilaments were present in all four surgically resected specimens. This tumor expands the list of soft tissue and bone tumors in which anomalous expression of intermediate filaments can occur but, more important, illustrates that changes in genetic expression of neoplasia of mesenchymal origin can result in paradoxic epithelial differentiation.     

Human osteogenic sarcoma: fine structure of the chondroblastic type

The fine structure of representative regions of four chondroblastic osteogenic sarcomas was studied. These regions contained four morphologically distinguishable subtypes of chondroblastlike cells. In addition, multinucleated giant cells, fibroblastlike cells, and macrophagelike cells were present, along with small populations of unclassifiable cells forming at least two subgroups of cells likely to be of a neoplastic nature. With only one exception, all types of chondroblastlike cells were separated by wide zones of extracellular matrix. The large multinucleated cells showed a fine structure that differed from that seen in multinucleated giant cells of other tissues. The evidence suggested that the multinucleated cells in the chondroblastic osteogenic sarcomas were active in phagocytic functions. It is not clear whether or not they are neoplastic in nature. Osteoblastlike cells were not encountered in the chondroid areas of the osteogenic sarcomas studied. On the basis of the findings it is concluded that the observed fine structural polymorphism of the chondroblastlike cells may reflect differences in maturation and differentiation among these cells. The most well-differentiated cells (type 1) appear to be able to exert secretory functions.     

Intriguing Case: Primitive Pelvic Sarcoma Resembling Clear Cell Sarcoma of Kidney

Clear cell sarcoma of kidney (CCSK) is an aggressive childhood renal tumor of unknown histogenesis that has not been reported to occur outside the kidney. The article describes an extrarenal neoplasm arising in the pelvic soft tissues of a 13-year-old boy that was composed predominantly of uniform mesenchymal cells with optically clear cytoplasm supported by an arborizing network of small blood vessels, which was indistinguishable in appearance from CCSK. The electron microscopic findings, although nonspecific, were essentially identical to those of CCSK, with tumor cells displaying fine chromatin, electron-lucent cytoplasm, and intercellular collagen but no evidence of tissue-specific differentiation. Immunocytochemical studies showed positivity for vimentin but negative results for desmin, myoglobin, cytokeratin, epithelial membrane antigen, S-100 protein, neuron-specific enolase and factor VIII-related antigen. Tumor cells were also nonreactive with Ulex lectin. This unusual pelvic tumor and CCSK may both derive from primitive mesenchymal cells and may represent phenotypic but not necessarily histogenetic analogs.     

Intriguing Case: Primitive Pelvic Sarcoma Resembling Clear Cell Sarcoma of Kidney

Clear cell sarcoma of kidney (CCSK) is an aggressive childhood renal tumor of unknown histogenesis that has not been reported to occur outside the kidney. The article describes an extrarenal neoplasm arising in the pelvic soft tissues of a 13-year-old boy that was composed predominantly of uniform mesenchymal cells with optically clear cytoplasm supported by an arborizing network of small blood vessels, which was indistinguishable in appearance from CCSK. The electron microscopic findings, although nonspecific, were essentially identical to those of CCSK, with tumor cells displaying fine chromatin, electron-lucent cytoplasm, and intercellular collagen but no evidence of tissue-specific differentiation. Immunocytochemical studies showed positivity for vimentin but negative results for desmin, myoglobin, cytokeratin, epithelial membrane antigen, S-100 protein, neuron-specific enolase and factor VIII-related antigen. Tumor cells were also nonreactive with Ulex lectin. This unusual pelvic tumor and CCSK may both derive from primitive mesenchymal cells and may represent phenotypic but not necessarily histogenetic analogs.     

Ultrastructural Similarities and Differences of Synovial Sarcoma, Epithelioid Sarcoma, and Clear Cell Sarcoma of the Tendons and Aponeuroses

The ultrastructural features of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses were compared to identify differential markers and similarities. A continuous spectrum of modulation of morphologic features of synovial and epithelioid sarcomas was observed. Biphasic synovial sarcoma with pseudoglandular and stromal components represents one extreme of this spectrum. The gradual disappearance of the pseudoglands and the formation of nests of epithelial-like cells, which are characteristic of epithelioid sarcoma, were observed. The cells of clear cell sarcoma, as well as those of synovial and epithelioid sarcomas, form epithelial-like islands; however, the presence of premelanosomes in the former is a feature of neural crest derivatives.     

Ultrastructural Similarities and Differences of Synovial Sarcoma,Epithelioid Sarcoma,and Clear Cell Sarcoma of the Tendons and Aponeuroses

The ultrastructural features of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses were compared to identify differential markers and similarities. A continuous spectrum of modulation of morphologic features of synovial and epithelioid sarcomas was observed. Biphasic synovial sarcoma with pseudoglandular and stromal components represents one extreme of this spectrum. The gradual disappearance of the pseudoglands and the formation of nests of epithelial-like cells, which are characteristic of epithelioid sarcoma, were observed. The cells of clear cell sarcoma, as well as those of synovial and epithelioid sarcomas, form epithelial-like islands; however, the presence of premelanosomes in the former is a feature of neural crest derivatives.     

Alveolar Soft-Part Sarcoma Diagnosed by Fine Needle Aspiration Biopsy and Electron Microscopy

Abstract

A case of alveolar soft-part sarcoma diagnosed by fine needle aspiration cytology is reported. The cytologic findings from both Diff-Quick and Pananicolaou stained slides showed cells arranged in both clusters and individually, with rare groups of cells mimicking an alveolar pattern. The individual cells showed minimal nuclear pleomorphism and eccentrically placed vesicular nuclei; some had 1 to 2 small prominent nucleoli and moderate amounts of granular cytoplasm. These features are suggestive of alveolar softpart sarcoma in the appropriate clinical setting. The cytopathologic diagnosis was subsequently confirmed by the histopathologic study of the cell block preparation and by the electron microscopy submitted from the aspirated material. (The J Histotechnol 16:375, 1993)     

A classical osteogenic sarcoma of the breast: histology, immunohistochemistry and ultrastructure

A classical osteogenic sarcoma of the breast is described and the results of light microscopy, including immunohistochemistry for epithelial and mesenchymal markers, and of electron microscopy are presented. No epithelial features were detected by any of the methods used, the tumour being considered a true osteogenic sarcoma. The tumour appears to have arisen de novo, and not from a pre-existing fibroadenoma.     

Chordomalike Soft Tissue Sarcoma in the Leg: A Light and Electron Microscopic and Immunohistochemical Study

A soft tissue tumor in the leg of a 67-year-old woman is described. This large tumor below the knee area infiltrated extensively the deep and superficial soft tissues but did not involve the bones. The tumor cells formed nodules resembling the architecture seen in chondroid tumors and chordoma. The tumor cells were often vacuolized, and there was extracellular myxoid matrix similar to that in chordoma or myxoid chondrosarcoma. Immunohistochemistry showed keratins 8 and 19, epithelial membrane antigen, and vimentin in most tumor cells, and there was also S-100 protein positivity in a number of tumor cells. Electron microscopy showed desmosomelike cell junctions and bundles of intermediate filaments resembling those seen in many epithelial neoplasms. Thus the tumor resembled chordoma in many respects. Because clinically no other primary tumor was found, this tumor is probably a chordomalike primary soft tissue sarcoma different from typical extraskeletal myxoid chondrosarcoma or chordoid sarcoma.     

Chordomalike Soft Tissue Sarcoma in the Leg: A Light and Electron Microscopic and Immunohistochemical Study

A soft tissue tumor in the leg of a 67-year-old woman is described. This large tumor below the knee area infiltrated extensively the deep and superficial soft tissues but did not involve the bones. The tumor cells formed nodules resembling the architecture seen in chondroid tumors and chordoma. The tumor cells were often vacuolized, and there was extracellular myxoid matrix similar to that in chordoma or myxoid chondrosarcoma. Immunohistochemistry showed keratins 8 and 19, epithelial membrane antigen, and vimentin in most tumor cells, and there was also S-100 protein positivity in a number of tumor cells. Electron microscopy showed desmosomelike cell junctions and bundles of intermediate filaments resembling those seen in many epithelial neoplasms. Thus the tumor resembled chordoma in many respects. Because clinically no other primary tumor was found, this tumor is probably a chordomalike primary soft tissue sarcoma different from typical extraskeletal myxoid chondrosarcoma or chordoid sarcoma.     

Ultrastructure of Kaposi Sarcoma

Kaposi sarcoma (KS) is a complex disease with aspects of virology (human herpesvirus-8, HHV-8, and human immunodeficiency virus, HIV), immunology (immunodeficiency), hyperplasia (multiple widely spaced de novo lesions), and neoplasia (metastases) that has always been the most common AIDS-defining malignancy. The lesional spindle cell has been classified as being derived from either blood vascular or, more recently, lymphatic endothelial cell origin. This study revealed a spectrum of endothelial cell ultrastructure from lymphatic to blood vascular. It demonstrated frequent Weibel-Palade bodies and gap junctions. The spindle cells were shown to behave as facultative phagocytes, internalizing and processing necrotic cells and leaked red blood cells (RBCs). Fragmented RBCs were equivalent to the “hyaline droplets” seen by light microscopy. The final stages of RBC disintegration were hemosiderin and ferritin. Most significantly, this study disclosed that KS is actually composed of a single type of randomly oriented spindle cell forming vessels of varying size and integrity.     

Distinct Effects of RGD-glycoproteins on Integrin-Mediated Adhesion and Osteogenic Differentiation of Human Mesenchymal Stem Cells

The detailed interactions of mesenchymal stem cells (MSCs) with their extracellular matrix (ECM) and the resulting effects on MSC differentiation are still largely unknown. Integrins are the main mediators of cell-ECM interaction. In this study, we investigated the adhesion of human MSCs to fibronectin, vitronectin and osteopontin, three ECM glycoproteins which contain an integrin-binding sequence, the RGD motif. We then assayed MSCs for their osteogenic commitment in the presence of the different ECM proteins.As early as 2 hours after seeding, human MSCs displayed increased adhesion when plated on fibronectin, whereas no significant difference was observed when adhering either to vitronectin or osteopontin. Over a 10-day observation period, cell proliferation was increased when cells were cultured on fibronectin and osteopontin, albeit after 5 days in culture. The adhesive role of fibronectin was further confirmed by measurements of cell area, which was significantly increased on this type of substrate. However, integrin-mediated clusters, namely focal adhesions, were larger and more mature in MSCs adhering to vitronectin and osteopontin. Adhesion to fibronectin induced elevated expression of α₅-integrin, which was further upregulated under osteogenic conditions also for vitronectin and osteopontin. In contrast, during osteogenic differentiation the expression level of β₃-integrin was decreased in MSCs adhering to the different ECM proteins. When MSCs were cultured under osteogenic conditions, their commitment to the osteoblast lineage and their ability to form a mineralized matrix in vitro was increased in presence of fibronectin and osteopontin.Taken together these results indicate a distinct role of ECM proteins in regulating cell adhesion, lineage commitment and phenotype of MSCs, which is due to the modulation of the expression of specific integrin subunits during growth or osteogenic differentiation.