Histochemistry of Kaposi's sarcoma. I. Hydrolases and phosphorylase

Expression of endothelial cell markers PAL-E and EN-4 and Ia-antigens in Kaposi's sarcoma

Eleven biopsy specimens of Kaposi's sarcoma (KS) removed from the skin and oral mucosa were examined immunohistochemically with monoclonal antibodies PAL-E and EN-4, specific for human vascular endothelial cells, and with LN-3 monoclonal antibody reactive with immune-associated (Ia) antigens in the HLA-DR locus. The early lesions of KS, corresponding to the patch phase, contained hyperplastic venules and an increased number of lymphatic capillaries. The lymphatic capillary endothelium was reactive with EN-4, whereas, PAL-E reacted only with blood vessel endothelial cells. The spindle cells, like lymphatic endothelial cells, were non-reactive with PAL-E but showed positive reaction with EN-4 antibodies. The observed morphologic pattern of vasculogenesis and the demonstrated immune-reactivity in KS support an origin from the venule-lymphatic junction. This is an aberrant pattern but reminiscent of normal embryonal lymphatic channel development. The lymphatic capillaries and vascular slits were nonreactive with LN-3 antibody, but it was positive on cell membranes in a number of spindle cells, suggesting the focal expression of Ia-antigens.

Kaposi's sarcoma in AIDS: basement membrane and endothelial cell markers in late-stage lesions

Early-stage lesions of Kaposi's sarcoma (KS) are composed of single-layered, highly flattened cells lining collagen bundles, whereas late-stage lesions contain densely packed, spindle-shaped cells. We examined the progression of KS lesions in oral mucosa and lymph nodes from patients with AIDS, using antibodies specific for blood vascular endothelial cells (Factor VIII-related antigen) and their basement membrane (Type IV collagen and laminin). In addition, the plant lectin Ulex europaeus, which selectively stains blood vessels, was also used. In early-stage KS lesions, fibronectin, laminin and Type IV collagen were co-distributed at the interface between KS cells and collagen bundles; Factor VIII-related antigen and Ulex europaeus lectin staining was present in vascular channels and in the KS cells. However, in late-stage lesions, few if any KS cells stained with antibody to Factor VIII-associated antigen, although endothelial cells lining blood vessels were positive. Strong staining for laminin and Type IV collagen was present in a pericellular pattern throughout the nodular late-stage lesions. Since lymphatic capillary endothelium does not produce basement-membrane-specific macromolecules, these results support the conclusion that KS cells are related to blood vascular endothelium but eventually lose certain endothelium-specific markers as the cells are transformed into the spindle-shaped cell type.

Disseminated Kaposi's sarcoma in AIDS: histogenesis-related populations and influence of long-term treatment with rIFN-alpha A

Lesions (n = 19) of cutaneous Kaposi's sarcoma in different stages of development were obtained from 13 patients with acquired immunodeficiency syndrome (AIDS), and studied by light and electron microscopy. Six additional biopsies from 4 patients treated with recombinant alpha A interferon were obtained after treatment. Varying amounts of two proliferating cell populations were found: (1) Large cells showing cytologic and histochemical characteristics of endothelial cells. They were seen in close proximity to normal vessels, forming new vascular structures and large aggregates found in papular and nodular lesions. (2) Smaller spindle-shaped cells, probably of pericytic origin. They appeared in bundles and fascicles in the papillary dermis of the cutaneous Kaposi's sarcoma lesions and, in part, gave origin to thin-walled, bizarre-shaped vessels that show incomplete lumina proliferating from the upper to the deep dermis and are surrounded by extravasate erythrocytes and siderophages. After long-term systemic treatment with recombinant alpha A interferon, the endothelial type of tumor cell aggregates mostly disappeared, whereas most of the spindle-shaped pericytic-like cells were still present. Our findings lead us to suggest that some cellular product may, as a promoter factor, induce the proliferation and growth of endothelial cells. This factor may be blocked by alpha A interferon and cause regression of endothelial cell proliferation observed in AIDS patients undergoing long-term systemic therapy.

Kaposi's sarcoma in homosexual men: an immunohistochemical study

A recent outbreak of disseminated Kaposi's sarcoma has been recognized in homosexual men in New York, San Francisco, and Los Angeles. Biopsy specimens of skin lesions were obtained from nine of these homosexual men in Los Angeles and San Francisco. T lymphocyte subset antigens, factor VIII-related antigen, and HLA-Dr antigen were evaluated in situ in frozen sections using immunoperoxidase technics. Factor VIII-related antigen and HLA-Dr antigen were present on tumor cells, supporting a vascular endothelial origin of this neoplasm. Langerhans cells and T lymphocytes were present in numbers similar to that of normal skin in skin specimens from seven patients with Kaposi's sarcoma with visceral dissemination, but were increased in specimens from two patients with only cutaneous involvement.

[The histogenesis of Kaposi sarcoma: a histochemical and electronmicroscopical study (author's transl)]

1. Histologically, Morbus Kaposi is primarily characterized by a proliferation of streams composed of spindle-shaped cells, by vascular slits lined by cells, and by a minor cellular inflammatory reaction. 2. The cells lining the vascular slits resemble endothelial cells and exhibit strong alkaline phosphatase activity and a clear leucinaminopeptidase activity. They contain Weibel-Palade bodies. 3. The ultrastructural analysis of the tumor cells shows a proliferative formation resembling capillary sprouts with and without lumina. The lumina are composed primarily of poorly differentiated endothelial cells. A second typical cellular component are fibroblast-like tumor cells possibly derived from perithelial cells. 4. Indicative of M.K. are also extravasation and phagocytosis of erythrocytes with intracytoplasmic decomposition, and storage of myelinlike structures somewhat resembling Schwannian-cells. 5.

CONCLUSION

M.K. is characterized by a multifocal neoplasia of capillary like structures and by a progressive sarcomatous development.