Myogenic cells in Kaposi's sarcoma: an ultrastructural study

Kaposi's Sarcoma: A Clinico-Pathologic Overview

A careful overview of the classical appearances of Kaposi's sarcoma (KS) as well as of its variants were reviewed from the clinical and pathological point of view. The growth phases (stages) and the cellular patterns were histopathologically compared with emphasis on the developmental progression of disease as well as mitotic activity. Other morphological aspects were also assessed such as the features of the early phases and the incidence of hyaline bodies. One hundred and forty-three lesions from 96 patients mostly of the Italian sporadic type were investigated. A complete list of those entities which should be considered in differential diagnosis is shown and the dilemma of whether KS is a neoplasia or a hyperplasia is discussed.

Human Mesenchymal Stem Cells of Diverse Origins Support Persistent Infection with Kaposi's Sarcoma-Associated Herpesvirus and Manifest Distinct Angiogenic, Invasive, and Transforming Phenotypes

Kaposi's sarcoma (KS), a highly angiogenic and invasive tumor often involving different organ sites, including the oral cavity, is caused by infection with Kaposi's sarcoma-associated herpesvirus (KSHV). Diverse cell markers have been identified on KS tumor cells, but their origin remains an enigma. We previously showed that KSHV could efficiently infect, transform, and reprogram rat primary mesenchymal stem cells (MSCs) into KS-like tumor cells. In this study, we showed that human primary MSCs derived from diverse organs, including bone marrow (MSCbm), adipose tissue (MSCa), dental pulp, gingiva tissue (GMSC), and exfoliated deciduous teeth, were permissive to KSHV infection. We successfully established long-term cultures of KSHV-infected MSCa, MSCbm, and GMSC (LTC-KMSCs). While LTC-KMSCs had lower proliferation rates than the uninfected cells, they expressed mixtures of KS markers and displayed differential angiogenic, invasive, and transforming phenotypes. Genetic analysis identified KSHV-derived microRNAs that mediated KSHV-induced angiogenic activity by activating the AKT pathway. These results indicated that human MSCs could be the KSHV target cells in vivo and established valid models for delineating the mechanism of KSHV infection, replication, and malignant transformation in biologically relevant cell types.

IMPORTANCE

Kaposi's sarcoma is the most common cancer in AIDS patients. While KSHV infection is required for the development of Kaposi's sarcoma, the origin of KSHV target cells remains unclear. We show that KSHV can efficiently infect human primary mesenchymal stem cells of diverse origins and reprogram them to acquire various degrees of Kaposi's sarcoma-like cell makers and angiogenic, invasive, and transforming phenotypes. These results indicate that human mesenchymal stem cells might be the KSHV target cells and establish models for delineating the mechanism of KSHV-induced malignant transformation.

Manipulation of endothelial cells by KSHV: implications for angiogenesis and aberrant vascular differentiation

Kaposi sarcoma (KS), a viral cancer associated to Kaposi sarcoma herpesvirus (KSHV) infection, is currently the most common tumor in men in sub-Saharan Africa. KS is an angiogenic tumor and characterized by the presence of aberrant vascular structures in the lesion. Although our understanding of how KSHV causes the aberrant differentiation of endothelial cells and the typical vascular abnormalities in KS tumors is far from complete, the experimental evidence reviewed here provides a comprehensive description of the role of KSHV in the pathogenesis of this unusual tumor. In contrast to other tumor viruses, whose interference with cellular processes relating to cell cycle, apoptosis and DNA damage may be at the heart of their oncogenic properties, KSHV may cause KS primarily by its ability to engage with the differentiation and function of endothelial cells. Although the intracellular pathways engaged by KSHV in the endothelial cells are being explored as drug targets, a better understanding of the impact of KSHV on endothelial cell differentiation and vasculogenesis is needed before the encouraging findings can form the basis for new targeted therapeutic approaches to KS.

Subpopulations of stromal cells from long-term human bone marrow cultures: ontogeny of progenitor cells and expression of growth hormone receptors

Long-term culture of bone marrow derived stromal colony forming cells (S-CFC) in matrix and nutrient defined agar medium resulted in stromal cell colonies that pass sequentially through three distinct morphological stages: firstly, aggregated loose syncytium of round to avoid cells (stage I), a second developmental stage of large branching colonies in which the cells become enlarged, elongated with cytoplasmic projections forming a loosely anastomized network with adjacent cells (stage II), and finally cells become dissociated, loosing their long, thin cytoplasmic filaments and breaking their contacts with one another, but remain large and retain a bi-polar nature (stage III). Cells were also grown in liquid medium in a culture microenvironment closely resembling conditions of haemopoiesis in vitro. Using a panel of well defined monoclonal antibodies reactive against the rat, rabbit and human growth hormone receptors, this study found immunochemical evidence of the presence and localization of binding sites of growth hormone (GH) in the cell membrane and extra-nuclear Golgi area of long-term bone marrow derived human stromal cells in liquid and semi-solid nutrient agar mediums. GH-receptor immunoreactivity was present in small proliferating progenitor cells, myofibroblast-like cells, large reticular fibroblast cells, adipocytes and endothelial cells. Only MAb known to be reactive against human tissue resulted in strong immunoreactivity. The expression of GH-receptors not only on small proliferating, but also on the well differentiated cells, indicates a role for growth hormone on non-progenitor cells. GH-receptor immunoreactivity on differentiating and/or differentiated cells suggests that GH is also necessary for, or has a trophic function in differentiation. We propose that direct GH action is necessary not only for differentiation of progenitor cells as implied by the dual effector hypothesis, but also their subsequent clonal expansion, differentiation and maintenance.

Solitary cutaneous myofibromas in adults: report of six cases and discussion of differential diagnosis

Six solitary, dermal or subcutaneous lesions occurring in adult patients are presented. These masses had a circumscribed, lobulated configuration; they were composed of fusiform and epithelioid cells that lacked atypical nuclear features. The pattern of growth featured fascicles and nests, a myxofibrous stroma, and prominent blood vessels with a focally "hemangiopericytoid" appearance. Immunohistochemical analyses showed uniform reactivity for vimentin and alpha isoform-actin, with negativity for desmin and neural determinants. The overall appearance of the lesions was similar to that of "infantile myofibromatosis," and corresponded to previous descriptions of "solitary myofibroma(tosis)" in adults. Immunophenotypic and ultrastructural support exists for a proposed myofibroblastic nature for such proliferations. Differential diagnostic considerations include neurothekeomas, plexiform fibrous histiocytomas, nodular fasciitis, cutaneous inflammatory pseudotumors, dermatomyofibromas, leiomyomas, and other forms of fibromatosis affecting the skin and superficial soft tissues.

Platelet activating factor produced in vitro by Kaposi's sarcoma cells induces and sustains in vivo angiogenesis

Imbalance in the network of soluble mediators may play a pivotal role in the pathogenesis of Kaposi's sarcoma (KS). In this study, we demonstrated that KS cells grown in vitro produced and in part released platelet activating factor (PAF), a powerful lipid mediator of inflammation and cell-to-cell communication. IL-1, TNF, and thrombin enhanced the synthesis of PAF. PAF receptor mRNA and specific, high affinity binding site for PAF were present in KS cells. Nanomolar concentration of PAF stimulated the chemotaxis and chemokinesis of KS cells, endothelial cells, and vascular smooth muscle cells. The migration response to PAF was inhibited by WEB 2170, a hetrazepinoic PAF receptor antagonist. Because neoangiogenesis is essential for the growth and progression of KS and since PAF can activate vascular endothelial cells, we examined the potential role of PAF as an instrumental mediator of angiogenesis associated with KS. Conditioned medium (CM) from KS cells (KS-CM) or KS cells themselves induced angiogenesis and macrophage recruitment in a murine model in which Matrigel was injected subcutaneously. These effects were inhibited by treating mice with WEB 2170. Synthetic PAF or natural PAF extracted from plasma of patients with classical KS also induced angiogenesis, which in turn was inhibited by WEB 2170. The action of PAF was amplified by expression of other angiogenic factors and chemokines: these included basic and acidic fibroblast growth factor, placental growth factor, vascular endothelial growth factor and its specific receptor flk-1, hepatocyte growth factor, KC, and macrophage inflammatory protein-2. Treatment with WEB 2170 abolished the expression of the transcripts of these molecules within Matrigel containing KS-CM. These results indicate that PAF may cooperate with other angiogenic molecules and chemokines in inducing vascular development in KS.

CD31 immunoreactivity in mesenchymal neoplasms of the skin and subcutis: report of 145 cases and review of putative immunohistologic markers of endothelial differentiation

CD31 has recently been reported as a specific marker of endothelial differentiation among non-hematopoietic human neoplasms. In order to address this contention in particular regard to tumors of the skin and subcutis, the authors undertook a comparative study that surveyed 145 mesenchymal lesions. The antibodies used were directed against CD31 (clone JC/70A) and CD34 (clone My10), and these were compared with binding of Ulex europaeus I agglutinin (UEA). Proliferations that were included in the category of vascular tumors included cavernous and capillary hemangiomas (17 cases); lymphangiomas (8); epithelioid ("histiocytoid") hemangiomas (3), papillary endovascular hemangioendothelioma (1), angiosarcoma (7), and Kaposi's sarcoma of the mixed angiomatoid and spindle-cell type (17). CD31-immunoreactivity was observed in 35 of 53 vascular lesions; the neoplastic cells in a single angiosarcoma and the spindle cells in each case of Kaposi's sarcoma (KS) were not labeled. In all of the latter tumors, however, staining for CD31 was identified in the endothelia of angiomatoid areas and non-neoplastic blood vessels. These results compared favorably with those seen with anti-CD34, which decorated 36 of 53 vascular tumors--including 8 of 17 KS cases--and UEA, which bound to the neoplastic cells of 36 lesions. In contrast, all of 92 non-endothelial tumors included in this study (34 nerve sheath tumors [30 benign; 4 malignant]; 39 fibrohistiocytic neoplasms [11 benign; 28 malignant]; 9 smooth muscle tumors [6 benign; 3 malignant]; 7 glomus tumors; and 3 giant cell fibroblastomas) were negative for CD31. UEA labeled 3 non-vascular neoplasms, whereas 38 lesions of that type were CD34-positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemistry of Kaposi's sarcoma-like tumor cells from pigtailed macaques with simian AIDS

Some macaques infected with SRV-2 developed SAIDS and RF, a Kaposi's sarcoma (KS)-like tumor. We investigated the immunophenotypic markers of this SAIDS-associated retroperitoneal fibromatosis (RF). RF tumor is characterized by proliferation of spindle cells accompanying inflammatory cell infiltrates, fibroblasts, and endothelial cells. RF spindle cells in tumor tissues revealed several immunobiologic characteristics similar to vascular smooth-muscle cells or myofibroblasts based on positive immunoreactivity of smooth-muscle alpha-actin and desmin. The majority of cultured RF spindle cells also expressed specific markers for vascular smooth muscle. These results suggest that the RF spindle cells are derived from vascular smooth-muscle cells. Furthermore, RF tissues and cells were persistently infected with SRV-2, which may play an important role in viral etiology of AIDS-associated neoplasm in this macaque model.

Co-expression of endothelial cell and macrophage antigens in Kaposi's sarcoma cells

The histopathogenesis of Kaposi's sarcoma (KS) was investigated using immunocytochemistry in 12 skin biopsies obtained from two AIDS patients, nine patients with the classic form, and one organ-transplant patient. KS cells revealed a peculiar antigenic profile, being characterized by co-expression of endothelial and macrophage markers. KS cells were stained for von Willebrand factor (vWF); for vascular endothelial (VE) cadherin, an endothelial specific adhesion molecule; and for PECAM/CD31. In addition, they expressed the macrophage antigens PAM-1, CD68, and CD14, and were positive for vitronectin receptor and alpha-1,5,6/beta-1 integrins. KS cells were weakly stained for ICAM-1 in 6 of 12 cases and were negative for VCAM-1 and E-selectin.

Immunohistochemical and electron microscopic profiles of cutaneous Kaposi's sarcoma and bacillary angiomatosis

Thirty cases of cutaneous Kaposi's sarcoma (KS) were evaluated and compared with eight cases of acquired immunodeficiency syndrome (AIDS)-related bacillary angiomatosis (BA). The morphologic features of both lesions were studied by light and electron microscopy and by immunohistochemistry with monoclonal endothelial antibodies against CD34, BNH9, and factor VIII-related antigen as well as the lectins Ulex europaeus 1 and Psophocarpus tetragonolobus. Macrophage/monocyte markers used were alpha 1-antitrypsin, lysosome, Kp1 (CD68), and polyclonal factor XIIIa. Electron microscopic studies demonstrated that most of the spindle cells in KS showed a paucity of cell organelles and an absence of Weibel-Palade bodies (WPB), whereas the cells in BA showed activated endothelial cells with WPB. By immunohistochemistry the spindle cells in KS were consistently positive for CD34 only, whereas proliferating cells in BA expressed all endothelial markers used. Numerous cells expressing macrophage/monocyte markers were present surrounding both KS and BA, and a small number of similar cells were entrapped within both lesions. The results demonstrated a restricted immunohistochemical profile for endothelial cell markers in spindle cells of KS (CD34+) distinct from that of endothelial cells in BA. These findings suggest that the spindle cells in KS are poorly differentiated endothelial cells or that they belong to an endothelial cell subset with partial expression of endothelial phenotype.

Kaposi's sarcoma: a review of gene expression and ultrastructure of KS spindle cells in vivo

The ultrastructural features and the gene expression pattern of Kaposi's sarcoma (KS) spindle cells in vivo suggest that KS is a tumor of the mixed cell type. The expression pattern of cytokines and cytokine receptors in the tumor lesion, together with the results obtained from in vitro characterization of KS-derived cells, provide evidence that paracrine mechanisms of growth factor action are important for the maintenance of KS. The reports on virus infection of KS cells suggest an indirect role of virus infection in the induction of KS, most likely mediated by immunostimulation and subsequent production of cytokines.

Kaposi sarcoma in Okinawa

BACKGROUND

The authors encountered six patients with Kaposi sarcoma in Okinawa; one was classic type, two were associated with adult T-cell leukemia (ATL), one was with multiple myeloma, and two were with acquired immune deficiency syndrome (AIDS). In the classic type, many nodular lesions were seen on the skin of the extremities and a few on the trunk, some of which were ulcerated. Most lesions regressed in 1.5 years. In four other patients (three without AIDS and one with AIDS), many plaques and a few nodular lesions were seen on the trunk, face, and extremities. The other patient with AIDS showed Kaposi sarcoma only in the lymph nodes and perineural tissues in the abdomen.

METHODS

Immunohistochemical and lectin histochemical studies were done on deparaffinized sections and on cells cultured from small pieces of tumor mass from the classic type Kaposi sarcoma. Isolation of viruses from tumor tissue was also attempted.

RESULTS

Large numbers of endothelial cells lining irregular vascular spaces, and some spindle cells showed positive reactions for Factor VIII-related antigen, Ulex europaeus 1 (UEA-1) (E.Y. Labs, Inc., San Mateo, CA), Griffonia simplicifolia (GS-1) (E.Y. Labs, Inc.) lectins, and epidermal growth factor (EGF) receptor antigen. Cytomegalovirus (CMV), hepatitis B, herpes simplex virus (HSV) 1 and 2, papillomavirus antigens, and human immunodeficiency virus (HIV) p24 core antigen were not seen in any patients, except in the patient with AIDS in whom CMV was demonstrated in tissues adjacent to the tumor (Patient 6). In cell culture, elongated spindle cells proliferated in plate and also in three-dimensional cultures. The cells were positive immunohistochemically for Factor VIII-related antigen and EGF receptor. They also stained lectin histochemically with UEA-1 and GS-1. Tube formations were demonstrated by electron microscopic study.

CONCLUSIONS

Six cases of Kaposi sarcoma have been diagnosed within a short time span where this condition has previously been said to be rare. The studies suggest a vascular endothelial cell origin and growth factor regulated growth for this tumor.

Cytokines and growth factors in the pathogenesis of AIDS-associated Kaposi's sarcoma

In the past, the study of KS pathogenesis has been hampered by the lack of in vitro and in vivo experimental systems. Recently, the establishment of long-term cultures of KS spindle cells and the development of animal models have allowed a variety of studies on the pathobiology of the disease. The results from these studies, reviewed herein, indicate that KS is a cytokine-mediated disease and that inflammatory and angiogenic cytokines and the HIV-1 Tat protein cooperate in its induction and progression in HIV-1-infected individuals.

A histologic and flow cytometric study of Kaposi's sarcoma

One hundred forty-three biopsies of Kaposi's sarcoma (KS) from 96 patients were assessed histopathologically, and mitoses were counted. Ninety-seven samples from 66 patients were analyzed by flow cytometry. Six of 97 (5.8%) KS lesions were DNA aneuploid with a clustering around a DNA index of 1.5 (range, 1.4 to 1.6). The median percentage of S-phase plus G2-phase cells (%S + G2) was 16.7%. Increasing mitotic counts and %S + G2 were seen with progression of the phase and pattern of disease. Nodular KS and spindle cell predominant KS had the highest mitotic counts and %S + G2, with nodular KS larger than 4 mm having a higher mitotic count than those smaller than 4 mm. These findings suggest a low level of DNA aneuploidy in KS and important changes in the level of cell proliferation with the phase and pattern of the disease. However, flow cytometry does not solve the dilemma of whether KS is a hyperplastic or neoplastic process.

Alterations in tumor angiogenesis associated with stable expression of the HIV tat gene

Recent evidence suggests that the human immunodeficiency virus type 1 (HIV) trans-activator gene (tat) has transforming properties and may be a causative factor in the development of certain types of cancers, in particular Kaposi's sarcoma (i.e., Vogel J. et al. Nature 335:606-611, 1988). To help elucidate the potential role or roles of the HIV tat gene in neoplastic transformation, cell lines were constructed that constitutively express a functional tat gene product. HeLa cells were coelectroporated with two plasmids, one containing the HIV tat gene in an expression cassette and another containing the dominant selectable marker gene xanthine guanine phosphoribosyltransferase (XGPRT). After XGPRT selection, single-cell clones that expressed a functional tat protein were identified by measuring chloramphenicol acetyltransferase (CAT) activity after electroporating a plasmid containing the CAT gene transcriptionally controlled by HIV trans-activation-responsive region (tar). Phenotypic alterations resulting from the expression of tat were then determined. Control cells and tat-expressing cells grew at similar rates in culture. However, when grown as tumors in nude mice, tat-expressing cells produced a lower percentage of tumors, and the tumors that were produced either regressed, stopped growing, or grew at a very reduced rate compared with cells not expressing tat. These differences may have resulted from a tat-associated reduction in neovascularization in the tumors. A comparison of total cellular proteins by two-dimensional polyacrylamide gel electrophoresis indicated only one reproducible alteration in a polypeptide of approximately 44 kDa and pl of approximately 6.2 associated with tat expression. These cells may be very useful in future in vitro and in vivo studies designed to examine the effects of HIV tat on endothelial and vascular smooth-muscle cells and the role of tat in the etiology of Kaposi's sarcoma.

HIV-associated Kaposi's sarcoma: new developments in epidemiology and molecular pathology

New epidemiological data give evidence for an unknown etiological agent of Kaposi's sarcoma (KS). Experimental support is provided by research on cultivated KS cells. These results contradict a direct involvement of HIV-1 in the pathogenesis of KS. Research on cultivated KS cells confirmed the hypothesis that KS spindle cells originate from endothelial cells and gave new insight into the pathogenesis of tumor cell growth. KS spindle cells secrete an autocrine acting growth promoting activity. Nevertheless, they seem to depend on several growth factors like PDGF and IL-6 provided by surrounding endothelial cells and macrophages, respectively. The results support the hypothesis of a tumor relying on paracrine acting factors more than on autocrine acting factors.

Immunohistochemical evaluation of vascular neoplasms

Immunohistochemistry is of proven value in the evaluation of cutaneous vascular neoplasms. Nonetheless, the lack of sensitivity and specificity demonstrated by some endothelial markers requires that a panel of antibodies to other lineage-related determinants be applied in this context. Compared with electron microscopy, enzyme-linked antibody techniques can be applied in a cost-effective manner, with a satisfactory diagnostic result in most cases. The efficacy of these methods will likely improve as more sensitive and specific markers of endothelial differentiation are characterized. For the time being, the exclusion of non-endothelial proliferations remains an important aspect of the differential diagnosis of vascular tumors.

Angiogenic properties of Kaposi's sarcoma-derived cells after long-term culture in vitro

Cells derived from lung biopsies and pleural effusions from AIDS patients with Kaposi's sarcoma (KS) of the lungs were established in long-term culture with the aid of conditioned medium from HTLV-II-transformed T cells (HTLV-II CM). These AIDS-KS cells were similar to the so-called spindle cells in KS lesions and had some of their features. They produced factors that supported their own growth (autocrine) and the growth of other cells (paracrine), including umbilical vein endothelium and fibroblasts. That the AIDS-KS cells also expressed potent angiogenic activity was demonstrated by the chorioallantoic membrane assay and by subcutaneous inoculation of AIDS-KS cells into nude mice, which resulted in the development of angiogenic lesions composed of mouse cells and showing histological features similar to those of human KS lesions. These data suggest that AIDS-associated KS and possibly other types of KS may be initiated by signals that induce the growth of particular cells (spindle cells of lymphatic or vascular origin) and the expression of autocrine and paracrine activities.

Intraoral Kaposi's sarcoma: a correlated light microscopic, ultrastructural, and immunohistochemical study

Oral mucosal lesions of Kaposi's sarcoma are a common finding in patients with acquired immunodeficiency syndrome (AIDS). The histologic features of Kaposi's sarcoma vary, depending on the clinical stage of the lesion. Endothelium-lined vessels are the principal feature of early, macular lesions, while spindle cells dominate late-stage, nodular lesions. The histogenesis of both components remains controversial. In this study, biopsy specimens of intraoral Kaposi's sarcoma from 10 patients with AIDS were studied by light and electron microscopic examination and by immunoperoxidase staining with the endothelial markers, factor VIII-related antigen and Ulex europeaus agglutinin I. The results of this study support a vascular origin for both the endothelium-lined vessels and the spindle cells. The latter appear to represent vascular endothelial cells in various stages of differentiation. The histologic features that are useful in the diagnosis of intraoral Kaposi's sarcoma are reviewed.

Primary Kaposi's sarcoma of the lymph node in children

A case of primary Kaposi's sarcoma of the lymph node (single node involvement) is reported on here. It occurred in a white, Italian boy 10 years of age. An extensive review of the literature showed that this was only the second childhood case of the disease among non-acquired immune deficiency syndrome (AIDS)-related people of the Western world.

Invasive activity and chemotactic response to growth factors by Kaposi's sarcoma cells

Kaposi's sarcoma (KS) is a relatively low grade neoplasm, classically occurring in the skin of elderly men. A more virulent and invasive form of Kaposi's sarcoma has been described in patients with acquired immune deficiency syndrome (AIDS). The origin and identification of the tumor cells in these lesions is controversial. Here we have studied the behavior of cells derived from KS lesions in an in vitro assay which measures the ability of cells to invade through a reconstituted basement membrane. In agreement with previous work, KS cells obtained under selective culture conditions were invasive showing activity comparable to that of malignant tumor cells. Normal fibroblasts, smooth muscle cells, and endothelial cells did not demonstrate invasive behavior under the same experimental conditions. To characterize further the nature of the KS cells we tested the chemotactic response of cells from the most invasive line to a variety of growth factors and compared their response to those of fibroblasts, smooth muscle, and endothelial cells. These studies suggest that normal cells respond to a unique repertoire of chemotactic factors. The chemotactic response of the KS cells most closely resembled that of smooth muscle cells and was quite distinct from endothelial cells. These results indicate that the KS-derived cultures contain invasive cells with a smooth muscle cell-like phenotype.

Malignancies in the acquired immunodeficiency syndrome

Malignancies frequently arise in patients infected with human immunodeficiency virus (HIV), including those patients classified as having the acquired immunodeficiency syndrome (AIDS). Currently, Kaposi's sarcoma and certain types of lymphoma are considered to develop as a result of HIV infection, and other cancers have also been reported in these patients. For the most part, ultrastructural study of HIV-associated malignancies has been limited to Kaposi's sarcoma; the ultrastructural features of the epidemic form of this disease are generally the same as those of the classical form. The occurrence of these cancers in HIV-infected individuals appears to be related to the immunodeficiency caused by this virus, but the basic etiologic mechanisms remain unknown. In general, only palliative treatments are presently available for HIV-associated malignancies.

Initial lesions of HIV-related Kaposi's sarcoma--a histological, immunohistochemical, and ultrastructural study

Kaposi's sarcoma (KS) in human immunodeficiency virus infection (HIV) has become a rather frequent manifestation of the previously rare disease with fatal outcome. Initial lesions of KS were studied by means of histopathology, immunohistology, and electron microscopy in order to define the earliest alterations. The histopathological changes of initial lesions were distinct, consisting of (1) discrete proliferation of capillary vessels, (2) dissection of collagen by proliferating spindle cells which formed slits, (3) atypical spindle cells arranged in an Indian file pattern, and (4) the lack of any inflammatory cellular infiltrate. Double staining with antibodies against vimentin and immunohistochemical markers for endothelial cells revealed that slits forming vimentin-positive spindle cells displayed laminin, factor VIII, and PAL-E. Atypical vimentin-positive spindle cells arranged in an Indian file pattern inconsistently expressed laminin and factor VIII, but not PAL-E. KS cells rarely stained with the lectin UEA I, not even in case of less advanced dedifferentiation. Electron microscopy showed gradual transformation between spindle cells forming slits and those having lost the ability to form incomplete vessel walls. The present findings support the view that KS develops from the endothelial cells of the blood vessels. The proliferation of atypical endothelial cells as early as in initial lesions and the lack of inflammation favors the primary neoplastic genesis of KS.

In vitro study of the cell populations in two cases of Kaposi's sarcoma

Despite numerous studies, the histogenesis of Kaposi's sarcoma remains unclear. In connection with the culture of two Kaposi's sarcomas, the morphological, ultrastructural, and immunological properties of the various cell types observed are discussed. Cloning in agar, loss of contact inhibition, and karyotyping were used to determine which cells had undergone malignant transformation. Findings for both cases revealed that endothelial cells had undergone neoplastic transformation. Fibroblastic cell lines were isolated from both sarcoma fragments; although their growth characteristics distinguished them from normal fibroblasts (increased growth and possibility of culture in soft agar), cytogenetic investigations on both lines confirmed that they were genetically normal, and occurred along with malignant cells as a accessory compartment within lesions. Endothelial cells appear to be the sole origin of Kaposi's sarcoma, and may release factors which alter fibroblastic growth.

An immunohistological study of factor VIII related antigen and Kaposi's sarcoma using polyclonal and monoclonal antibodies

Immunohistochemical techniques have been used to demonstrate Factor VIII related antigen (FVIIIRA) in endothelial cells and to study a variety of tumours including Kaposi's sarcoma. Conflicting reports on the presence of this antigen within the spindle cells of Kaposi's sarcoma have been made. These differences may be due to variations in techniques, in the immunoreagents used and in the method of fixation and handling of the specimen. A major factor may also be the lack of a uniform interpretation of positive peroxidase labelling. This study was confined to paraffin-embedded tissues and compared the results and distribution of FVIIIRA labelling in Kaposi's sarcoma using two commercially available polyclonal antibodies and three monoclonal antibodies. The effects of predigesting the sections with trypsin and protease were also evaluated. Positive labelling of tumour spindle cells was accepted only when it matched that seen in labelled endothelial cells. The polyclonal antibodies provided satisfactory localization of FVIIIRA and gave positive results more frequently than the monoclonal antibodies both with and without enzyme digestion. Endothelial labelling was evident in vessels both within and around the tumour but none was seen in the tumour spindle cells. Most previous studies gave no definition of positive labelling but spindle cells were reported as labelled. However, in those few reports where a definition was given the findings are analogous to those in this report, demonstrating the importance of defining positive labelling.

Kaposi's sarcoma in renal transplant recipients. Ultrastructural and immunoperoxidase study of four cases

Tissues from four cases of Kaposi's sarcoma developing in renal transplant recipients were studied by light and electron microscopic examination and by immunoperoxidase staining for Factor-VIII-related antigen. Ultrastructurally, the tumors in all four cases contained a variable mixture of cells, including endothelial cells, pericytes, fibroblasts, and myofibroblasts. These findings support the origin of Kaposi's sarcoma from primitive vasoformative mesenchyme. Immunoperoxidase staining for Factor-VIII-related antigen was limited to endothelial cells. In one case intracytoplasmic virus-like tubular complexes were seen. The significance of this finding is briefly discussed.

Vascular tumors of the mammary gland. A histochemical and ultrastructural study

A total of five haemangiosarcomata and two benign haemangiomas arising in the mammary gland have been studied electron microscopically and by histochemical techniques. Malignant tumors were mainly composed of endothelial cells reactive to alkaline phosphatase and adenosine triphosphatase, and of pericytes and undifferentiated mesenchymal elements. A juvenile haemangioma showed a more structured wall with an increase of endoplasmic reticulum and filaments, and a diminution of membrane modulations and rod-like tubular bodies. A cavernous haemangioma showed an ultrastructure very similar to normal vessels. The ultrastructural and histochemical data suggest a blood vessel origin of mammary angiosarcomas and show that vascular neoplasms of the breast, benign or malignant, are composed of a combined proliferation of the different cell types present in the vessel wall, as described in other organs.

Patch stage Kaposi's sarcoma

The patch stage of Kaposi's sarcoma (KS) has been recently recognized as histologically distinct from that seen in well-developed violaceous nodules of KS. We report a patient with patch stage KS and its angioendothelioma-like histology. The presence of glomerulus-like vascular structures is a newly described feature.

Kaposi's sarcoma: venous capillary haemangioblastoma. A histochemical and ultrastructural study

Histochemical and ultrastructural studies in two patients with Kaposi's sarcoma revealed that spindle cells have the pattern of venous capillary endothelium.

Primary leiomyosarcoma of the bone and its comparison with fibrosarcoma

Two cases of primary leiomyosarcoma of the bone are recorded, one in the distal fibula of a 66-year-old man, the other in the proximal tibia of a 61-year-old woman. The cytological, histological, and ultrastructural features of leiomyosarcoma of bone are described and compared with those of fibrosarcoma. These features are sufficiently characteristic to enable a confident diagnostic distinction between leiomyosarcoma and fibrosarcoma. Nevertheless, certain basic similarities exist between these two tumors, manifested at the ultrastructural level by the presence of myofilaments in fibrosarcoma; it would seem that the observed differences relate to the degree of development of the myofilamentous structures. It is postulated that primary leiomyosarcoma of the bone need not necessarily always arise from the media of blood vessels; it might also conceivably develop through advanced myogenic metaplasia of a sarcoma originating from fibroblastic tissue.

Kaposi's sarcoma -- Case report and review of Japanese cases

A case of Kaposi's sarcoma in a 60 year-old male was examined histologically and electron microscopically. Multiple hemorrhagic skin lesions were confined within the scalp. The major part of initial skin biopsies exhibited capillary hemangiomatous component, but examination of surgical materials confirmed its nature as hemorrhagic sarcoma. At autopsy, the skin lesions showed various histological pictures ranging from angiomatous or granulomatous to sarcomatous proliferation of spindle-shaped cells. Of intriguing findings were the bone marrow involvement and the pulmonary changes, the former consisting of typical sarcomatous lesion and the latter being characterized by purpuric appearance of the pleura responsible for the terminal pneumohemothorax. Electron microscopically, the tumor cells showed Weibel-Palade granules in the cytoplasm suggesting the endothelial nature. In this article, Japanese autopsy cases of Kaposi's sarcoma so far reported are summarized.