The nature of hyaline (eosinophilic) globules and vascular slits of Kaposi's sarcoma.

Ultrastructural studies of Kaposi's sarcoma (KS) from skin biopsies of 24 patients (eight with acquired immunodeficiency syndrome (AIDS) and 16 without) were performed to delineate the nature of hyaline globules and vascular slits. These structures have been regarded as one of the important criteria for the recognition of KS under light microscopy. Histochemical and immunochemical studies were also performed to correlate with the electron microscopic (EM) observations. The most remarkable EM findings of KS were the intracytoplasmic lumen formation and erythrophagocytic activities of the neoplastic cells, particularly in the mature nodular, or neoplastic stage. The spindle-shaped or ovoid neoplastic cells frequently contained one to several intact and fragmented red blood cells. The intracellular and extravasated erythrocytes were often arranged in single files, giving these vascular slits an elongated appearance on longitudinal sections. The phagocytic activities of the neoplastic cells were demonstrated by the presence of membrane-bound lysosomes containing phagocytized erythrocytes and their partially digested forms (erythrophagosomes) adjacent to pinocytotic vesicles, prominent rough endoplasmic reticulum, and Golgi apparatus, as well as scattered, small, membrane-bound lysosomal granules, some of which were attached to the erythrophagosomes. The erythrophagosomes underwent various stages of disintegration. The partially digested red cells varied from 0.4 to 10 microns in diameter. The results of histochemical and immunochemical findings also strongly suggested that erythrophagosomes were most likely the hyaline globules (bodies) seen in light microscopy. The exact mechanism of erythrophagocytosis is uncertain. However, its consequences, erythrophagosomes, and intracytoplasmic lumen formation, particularly in the nodular or neoplastic stage in patients with and without AIDS, are among the important histologic features of KS.

The spindle-shaped cells in cutaneous Kaposi's sarcoma. Histologic simulators include factor XIIIa dermal dendrocytes.

Kaposi's sarcoma is a neoplasm that develops as multifocal lesions, often involving the skin, characterized by a complex histologic picture including numerous vascular spaces, perivascular and interstitial spindle-shaped cells, and extravasated erythrocytes, lymphocytes, and plasma cells. Using an antibody against factor XIIIa, which identifies dermal dendrocytes, numerous factor XIIIa-positive dermal dendrocytes were detected among the spindle-shaped cells in 12 acquired immune deficiency syndrome (AIDS)-associated, and five non-AIDS-associated Kaposi's sarcoma lesions. The factor XIIIa-positive dermal dendrocytes were also increased in histologic simulators of Kaposi's sarcoma such as dermatofibroma, angiomatoid malignant fibrous histiocytoma, granuloma annulare, and early wound healing, but were absent in keloids. The increased number of dermal dendrocytes, which are often in an angiocentric configuration and which also express CD4, lymphocyte function associated antigen-1 (LFA-1), and Leu M3 in Kaposi's sarcoma, may be important to the angioproliferative response. The results suggested that the spindle-shaped cells that are present in a variety of cutaneous lesions are dermal dendrocytes and belong to the reticuloendothelial system, unlike other mesenchymal cell types such as the endothelial cell. Apparently a diverse array of stimuli, including human immunodeficiency virus type-1 (HIV-1) infection and trauma, can stimulate the accumulation of factor XIIIa expressing dermal dendrocytes in the skin. These cells can then participate in different stages of a variety of cutaneous alterations including Kaposi's sarcoma, dermatofibroma, granuloma annulare, and early wound healing. Thus, the factor XIIIa-positive dermal dendrocyte is a common cellular denominator among diverse clinical entities that share some histologic features.

Pseudo-Kaposi's sarcoma occurring after placement of arteriovenous shunt. A case report with DNA content analysis.

Pseudo-Kaposi's sarcoma developed in a 51-year-old man 2 years after placement of an arteriovenous shunt for hemodialysis. Data from histopathologic, immunohistologic, and histochemical studies, electron microscopy, and DNA-cytometric analysis are presented.

Immunocytochemical profile of Kaposi's sarcoma cells: their reactivity to a panel of antibodies directed against different tissue cell markers.

Thirty-three cases of European Kaposi's sarcoma (KS) were investigated by immunohistochemical methods using a panel of antibodies specific for the markers of the cell types proposed for its histogenesis in the literature: S-100 protein for Schwann cells; lysozyme for histiocytes; alpha-actin, desmin and vimentin for pericytes and other mesenchyme-derived cells; factor VIIIR:Ag and Ulex europaeus agglutinin-I for endothelial cells. Antifibronectin antibodies were also used in order to investigate some functional activities of the proliferating cells. Immunohistochemical results showed that KS cells were diffusely positive for vimentin and alpha-actin and negative for all other cell markers. Furthermore, KS cells were constantly surrounded by fibronectin-positive material. Since the KS cells are diffusely positive for vimentin, they may be considered a monotypic proliferation of mesenchyme-derived cells which lack the markers of full endothelial cell differentiation; however, the occurrence of fibronectin-positive material around them suggests that these cells are actively proliferating endothelial cells and their diffuse positivity for alpha-actin suggests a possible differentiation to pericytic cells. In conclusion KS cells may be considered as mesenchymal cells which are at an intermediate stage of maturity or immaturity in vascular differentiation.

Hyaline bodies in Kaposi's sarcoma: an immunocytochemical and ultrastructural study.

The nature of hyaline bodies (HB) in Kaposi's sarcoma (KS) has been investigated by electron microscopy (EM) and immunohistochemical methods. Paraffin sections from 45 cases of KS selected on the basis of their high content of HB were challenged with antisera against factor VIIIR:Ag, carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), alpha 1-antitrypsin (A1AT), fibrinogen, hemoglobin, alpha-actin and lysozyme. HB showed positivity for all the antibodies except for the last two. By EM, HB showed features consistent with red blood cell, fibrin and platelet phagocytosis. Therefore, HB in KS are considered to be the expression of an indiscriminate process of phagocytosis which involves not only erythrocytes and platelets, but also other substances such as fibrinogen, factor VIIIR:Ag, A1AT, CEA and AFP.

Confirmation of early Kaposi's sarcoma by polyclonal antibody to type IV collagen.

By the use of polyclonal antibody to type IV collagen that binds to epitope(s) retained in routinely processed tissues, we have confirmed the presence of early Kaposi's sarcoma in skin lesions that were not diagnostic on histologic examination. This reagent is of considerable use, particularly in cases of rapidly developing Kaposi's sarcoma with acquired immunodeficiency syndrome in which histologic features may not be fully developed.

Processing, secretion, and biological properties of a novel growth factor of the fibroblast growth factor family with oncogenic potential.

We recently reported that the protein encoded in a novel human oncogene isolated from Kaposi sarcoma DNA was a growth factor with significant homology to basic and acidic fibroblast growth factors (FGFs). To study the properties of this growth factor (referred to as K-FGF) and the mechanism by which the K-fgf oncogene transforms cells, we have studied the production and processing of K-FGF in COS-1 cells transfected with a plasmid encoding the K-fgf cDNA. The results show that, unlike basic and acidic FGFs, the K-FGF protein is cleaved after a signal peptide, glycosylated, and efficiently secreted as a mature protein of 176 or 175 amino acids. Inhibition of glycosylation impaired secretion, and the stability of the secreted K-FGF was greatly enhanced by the presence of heparin in the cultured medium. We have used the conditioned medium from transfected COS-1 cells to test K-FGF biological activity. Similar to basic FGF, the K-FGF protein was mitogenic for fibroblasts and endothelial cells and induced the growth of NIH 3T3 mouse cells in serum-free medium. Accordingly, K-fgf-transformed NIH 3T3 cells grew in serum-free medium, consistent with an autocrine mechanism of growth. We have also expressed the protein encoded in the K-fgf protooncogene in COS-1 cells, and it was indistinguishable in its molecular weight, glycosylation, secretion, and biological activity from K-FGF. Taken together, these results suggest that the mechanism of activation of this oncogene is due to overexpression rather than to mutations in the coding sequences.

Detection of cytomegalovirus DNA in classic and epidemic Kaposi's sarcoma by in situ hybridization.

Several lines of evidence have suggested an etiologic association of cytomegalovirus (CMV) with Kaposi's sarcoma. This contention is supported by a pathoepidemiologic survey of 54 cases of acquired immunodeficiency syndrome (AIDS) at our own institution. Of the 27 patients with documented Kaposi's sarcoma, 24 (89%) showed histologic evidence of CMV infection (cytomegalic cells with viral inclusions), whereas only 9 (33%) of the patients with AIDS without Kaposi's sarcoma showed hallmarks of CMV infection. In an attempt to address this question further, we have searched for the presence of CMV nucleic acid sequences in a series of 25 patients with AIDS and Kaposi's sarcoma, using the technique of in situ DNA hybridization. The reliability of the in situ technique is demonstrated, and the technique is shown to be more sensitive than the detection of viral inclusions within Kaposi's sarcoma lesions by routine light microscopy. However, only 20% of our cases showed evidence of CMV involvement, and the CMV-positive cells within the affected Kaposi's sarcoma lesions were few and sparsely distributed. In addition, a companion series of 6 elderly patients with "classic" Kaposi's sarcoma showed no evidence of CMV infection by either conventional microscopy or in situ hybridization. These results do not support the notion of a strong association between Kaposi's sarcoma and CMV, unless the CMV sequences are present at a copy number too low for detection by these methods. The implications of these findings in light of current theories of CMV oncogenesis are discussed.

Eosinophilic globules in Kaposi's sarcoma. A histochemical, immunohistochemical, and ultrastructural study.

Of the 12 cases, 2 (17%) showed eosinophilic globules in the typical cutaneous type of Kaposi's sarcoma. The globules were stained with periodic acid-Schiff (PAS), periodic acid-Schiff reagent after diastase digestion, and phosphotungstic acid hematoxylin (PTAH), but were not stained with Mayer's mucicarmine, and alcian blue. As the results, these globules might be glycoprotein. The shape of the globules was very similar to glycoprotein globules of yolk sac tumor (endodermal sinus tumor) in the tissue of the ovary and testis. In the yolk sac tumor, similar globules are stained with alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, and alpha-1-antitrypsin using immunohistochemical techniques. Immunoperoxidase investigations were done with antibodies to alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, alpha-1-antitrypsin, and carcinoembryonic antigen in the eosinophilic globules of Kaposi's sarcoma, but these antigens were detected in the globules. The morphogenesis of the glycoprotein globules is not clear yet. A better understanding of the source of globules in Kaposi's sarcoma awaits further research.

Basement membrane and connective tissue proteins in early lesions of Kaposi's sarcoma associated with AIDS.

Nearly one-third of all young homosexual men diagnosed as having acquired immune-deficiency syndrome (AIDS) develop a disseminated form of dermal Kaposi's sarcoma (KS). Although the histogenesis of KS cells is unclear, certain evidence suggests that the aberrant cells are of endothelial derivation. We have examined the presence and distribution of connective tissue-specific and basement membrane-specific macromolecules by indirect immunofluorescence and immunoperoxidase staining of frozen sections in early cutaneous lesions of KS from individuals with AIDS. The KS cells typically line the spaces between collagen bundles of the reticular dermis. When stained for the connective tissue-specific glycoprotein fibronectin, all Kaposi's sarcoma lesions showed an intense staining pattern, revealing a complex array of linear deposits of antigen that outlined the exterior surface of the collagen bundles. Antibodies to laminin and type IV collagen, both basement membrane-specific macromolecules, produced an intense staining pattern similar to that found with the anti-fibronectin antiserum, indicating that all 3 antigens are closely codistributed. In contrast, antibodies to type I collagen, the major collagen of the dermis, uniformly stained the collagen bundles in the KS lesions and in the normal control skin. Antiserum to factor VIII-associated antigen, an antigen specific to blood vascular endothelium, frequently stained the KS lesions but the staining pattern was diffuse and of variable intensity. The results suggest that KS cells are derived from the endothelium of the blood microvasculature and maintain their secretory phenotype of secreting basement membrane-specific macromolecules.

[Kaposi's sarcoma: comparative immunohistochemical study and histogenic significance of endothelial markers]. / Sarcome de Kaposi: étude immunohistochimique comparative et intérêt histogénétique des marqueurs endothéliaux.

The origin of spindle-shaped cells in Kaposi's sarcoma (KS) remains controversial. Non-specific histochemical reactions, electron microscopic examinations and immunostainings using antibody against factor VIII-related antigen (F VIII-RAG) and Ulex europaeus agglutinin I (UEAI) lectin as endothelial markers have given contradictory results. Immunohistochemical techniques were applied to 7 frozen skin biopsy specimen of KS from 5 elderly Mediterranean people and 1 renal allograft recipient, and a group of 27 other frozen cutaneous tumours including haemangio and lymphangiosarcomas, benign vascular lesions and various epithelial, melanocytic, fibrohistiocytic, fibrosarcomatous and muscular tumours. Using UEAI and antibodies against F VIII-RAG, HLA-DR and vimentin, a large proportion of positive KS spindle cells was found in all cases whereas cells were negative for keratin. Among the various immunoreactivity patterns observed in this study, a unique immunohistochemical profile was demonstrated for KS, angiosarcoma and endothelial cell, which strongly supports the endothelial origin of spindle cells in KS. Whereas F VIII-RAG, HLA-DR, vimentin and UEAI were sensitive endothelial markers, only F VIII-RAG appeared specific for endothelial cells since UEAI stained 2 squamous cell carcinomas and HLA-DR and vimentin were present in various mesenchymal and melanocytic tumours.