The characteristics of human synovial tissue as seen with the electron microscope

Immunohistochemistry of normal human knee synovium: a quantitative study

OBJECTIVE

To describe the immunohistochemical characteristics of knee synovium from normal healthy subjects.

METHODS

12 healthy subjects underwent needle biopsy of knee synovium. Using antibodies directed against CD3, CD4, CD8, L26, Kp-1,and HLA-DR, detailed quantitative immunohistochemical analysis of various cell subpopulations was undertaken.

RESULTS

The mean (SD) age of the subjects was 37 (9) years (five male, seven female). All had a negative history for arthritis, no knee pain, and a totally normal joint examination except for the presence of retropatellar crepitus in five. For technical reasons staining for all immunohistochemical markers could not be achieved in all subjects. CD3+ T lymphocytes were seen in nine of 10 subjects, either diffusely or, more commonly, in perivascular areas. CD4+ cells were seen in synovium in three of seven subjects and CD8+ cells in six of eight subjects, in almost equal numbers (CD4:CD8, 1.1:1). L26+ B lymphocytes were not seen in any biopsy. Kp1+ macrophages were found in 10 of 10 subjects, predominantly in surface lining cells, and in small numbers in diffuse and perivascular locations. HLA-DR+ cells were seen in 10 of 10 subjects, predominantly in surface lining cells and diffusely, but a few were seen perivascularly.

CONCLUSIONS

Synovium from apparently normal subjects contained a wide range of different cell subpopulations but no B cells. The significance of these immune cells in normal synovium is unclear. A better understanding of their role in normal synovium may be important in analysing the transition to synovitis.

Synovial sarcoma: a review and update, with emphasis on the ultrastructural characterization of the nonglandular component

Classic biphasic synovial sarcoma is usually not a problem in identification, whereas the monophasic spindle cell form continues to be a challenge in the differential diagnosis of spindle cell neoplasms. Most synovial sarcomas do not arise from a joint or tendon sheath, and by electron microscopy and immunohistochemistry they differ in several ways from nonneoplastic synovium. The cell of origin of synovial sarcoma is unknown, but certain features are rather consistently observed in the biphasic tumors and are useful in identifying monophasic samples. These features are apparent by immunohistochemistry and electron microscopy, both of which indicate early epithelial differentiation in the nonglandular component of the neoplasm. With immunohistochemistry, some of these cells stain for keratin. By electron microscopy, a gradient of differentiation from unclassifiable spindle cells to fully differentiated epithelial lining cells is demonstrable. A review and illustration of the ultrastructural characteristics in this spectrum of intermediate cells constitute the main emphasis of the article. The cells tend to be oval and polygonal; to be arranged in clusters surrounded by basal lamina or flocculent matrix; to have junctions, including tight junctions, and to form villuslike filopodia, true microvilli, canaliculi, and microlumina. This range of ultrastructural features is usually diagnostic of the nonglandular phase of synovial sarcoma.

Synovial sarcoma: an electron microscopic study of monophasic and biphasic forms

Seven cases of synovial sarcoma were studied by electron microscopy. The 4 cases of the monophasic spindle type contained elongated cells arranged in sheets and cords; ultrastructurally the cells contained many cytoplasmic processes and were scattered in an amorphous matrix. The monophasic spindle type demonstrates ultrastructural characteristics that are unique and serve to differentiate it from the biphasic pattern and from fibrosarcoma. Three cases of the biphasic variety demonstrated cytologic characteristics of a true glandular epithelium and a malignant spindle cell stroma. The epithelial nature of the biphasic variety is a feature that raises doubt whether synovium is the stem cell.

A malignant tumor of the vagina resembling synovial sarcoma: a light and electron microscopic study

A malignant tumor arising in the upper lateral vaginal mucosa in a 24-year-old white woman, hitherto undescribed in the literature, was studied by light and electron microscopy. The main part of the tumor was epithelioid, forming a tubular or acinar pattern. At the periphery, the tumor cells were more spindly and formed sheets resembling fibrosarcoma. The tumor cells contained occasional material positive for mucicarmine, alcian blue, and PAS stains, and the nests of the cells forming acini were surrounded by reticulin fibers. The tumor ultrastructure consisted of a single type of cell with large cytoplasmic vacuoles and occasional perinuclear intracytoplasmic filaments. Slender long microvilli projecting into the lumina were also characteristic. Basal laminae were occasionally present around the acini. The findings suggested that the tumor was of mesenchymal origin, closely related to synovial sarcoma.

Ultrastructural changes in the synovial membrane in lipohaemarthrosis

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Ultrastructure of normal rat synovial membrane

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Synovial cells. A study of the morphology and an examination of protein synthesis of synovial cells

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Pathology of experimental haemarthrosis

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Ultrastructure of rabbit synovial membrane

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Synovial membrane in traumatic effusion. Ultrastructure and autoradiography with tritiated leucine

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A new inclusion body in rheumatoid synovia

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