The histogenesis of Kaposi's sarcoma (KS) tumor spindle cells (SC) remains controversial but several immunohistochemical studies favor a lymphatic origin. Twenty KS surgical biopsies were analyzed for the coexpression of LANA, CD34, LYVE-1, D2-40, VEGFR-2, VEGFR3 by using double or triple immunostaining. Most of the SC in both early and late KS expressed the lymphatic markers LYVE-1, D2-40 and VEGFR-3 and the blood vascular endothelial/endothelial precursor cell markers CD34 and endothelial stem cell marker VEGFR-2. All the LANA1 SC in early and late KS were LYVE-11, but only 75% of these LANA1 cells were CD341. The CD341/LANA1 cells increased from early-(68.8%) to late-stage KS (82.2%). However, approximately 18% of the LANA1 SC in early KS were CD342 but were LYVE-11, suggesting that resident lymphatic endothelial cells (LEC) are targeted for primary infection by human herpesvirus-8. This LANA1/LYVE-11/CD342 (resident LEC) cell population clearly decreased during the development of KS from early (18.7%) to late KS (2.9%). Thus, in late stages of KS, most SC were LANA1/CD341/LYVE-11. However, in both early-and late-stage KS, approximately 18% of the SC were CD341/ LANA-/LYVE-12 and could represent newly recruited endothelial precursor cells, which become infected in the lesion and eventually undergo a phenotype switch expressing LEC markers. Our study apparently indicates that KS represents a unique variant of tumor growth with continues recruitment of tumor precursor cells as well as proliferation and decreased apoptosis of SC. ' 2006 Wiley-Liss, Inc.Key words: Kaposi's sarcoma; HHV-8; KSHV; LANA; lymphangiogenesis; lymphatic; vascular endothelium; immunohistochemistry Kaposi's sarcoma (KS) presents as a highly vascularized tumorlike lesion affecting primarily the skin but which during development also disseminates to lymphnodes and viscera. 1 The lesions develop from early stages of patch/plaque to late nodular tumor lesions, 2 with characteristic early infiltration of mononuclear inflammatory cells, formation of atypical small blood vessels and vascular slits (angiogenesis), extravasations of erythrocytes and increased appearance of so-called spindle cells (SC) regarded as the tumor cells. 3 Unlike metastatic cancers, KS may also develop as multicentric tumor lesions, each arising from a focal reactive lesion and appearance of endothelial SC. 4 In 1994, a new herpesvirus was identified, namely, KS-associated herpesvirus or human herpesvirus-8 (KSHV/HHV-8), 5 which subsequently also was found in the other clinicoepidemiological forms of KS, 6-8 i.e., classic KS, iatrogenic KS, endemic KS (EKS) as well as in some rare, often AIDS-associated lymphoid disorders as primary effusion lymphoma 9 and multicentric Castleman's disease. 10 The HHV-8 latency-associated nuclear antigen type 1 (LANA-1) is consistently expressed in infected cells and considered necessary for the maintenance of HHV-8 infection. 11 The histogenesis of KS remains controversial but several immunohistochemical studies favor an endothelial origin...

corresponding to approximately 10% of KS registered during 1990-2005, were diagnosed (ELISA) as HIV-infected (OAKS) (74/78) and endemic KS (4/78). Females were 69.2% (54/78) with median age 31 and males 30.8% (24/78) with median age 38. More males (50%) had systemic KS than females (37%) and 4-times more multicentric OKS. All tested (34) oral KS patients sera had HHV-8 antibodies. Available (31/78) blood showed very low CD4 + T-lymphocyte counts. Most OKS (61.5%) had nodular histology. Immunostaining showed adult male nodular OAKS to have a significantly higher frequency of viral LANA + , endothelial CD34 + tumour spindle-cells (SC) and more Ki-67 + (median =24.1%) proliferating cells compared to females (17.2%). Juvenile nodular OAKS had more LANA + and Ki-67 + cells than corresponding adult cases. Significantly more LANA + and Ki-67 + cells were found in nodular OAKS compared to cutaneous HIV/AIDS Kaposi's sarcoma (CAKS). A positive correlation (60%) was found between the proliferation index (Ki-67 + cell frequency) and LANA + /CD34 + SC. OKS in Tanzania is since 1990, mostly seen in females, associated with HIV/AIDS and advanced (nodular) histopathology. Males have more systemic tumour burden while more females develop primary OAKS. HHV-8 + cells were more frequent in nodular male than female and in juvenile than adult nodular OAKS than cAKS. Higher tumoral HHV-8 content appeared to be correlated to proliferation index.

Kaposi's sarcoma (KS) is a highly and abnormally vascularized tumor-like lesion affecting the skin, lymphnodes and viscera, which develops from early inflammatory stages of patch/plaque to late, nodular tumors composed predominant of spindle cells (SC). These SC are infected with the Kaposi's sarcoma-associated herpesvirus or human herpesvirus-8 (KSHV/HHV-8). KS is promoted during HIV infection by various angiogenic and pro-inflammatory factors including HIV-Tat. The latency associated nuclear antigen type 1 (LANA-1) protein is well expressed in SC, highly immunogenic and considered important in the generation and maintenance of HHV-8 associated malignancies. Various studies favour an endothelial origin of the KS SC, expressing "mixed" lymphatic and vascular endothelial cell markers, possibly representing hybrid phenotypes of endothelial cells (EC). A significant number of SC during KS development are apparently not HHV8 infected, which heterogeneity in viral permissiveness may indicate that non-infected SC may continuously be recruited in to the lesion from progenitor cells and locally triggered to develop permissiveness to HHV8 infection. In the present study various aspects of KS pathogenesis are discussed, focusing on the histopathological as well as cytogenetic and molecular genetic changes in KS.

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The human gamma-herpes virus-8 (HHV-8) was first described in AIDS-related Kaposi's sarcoma (KS) tumour samples. In this study, we report comparative studies on paraffin-embedded biopsies of AIDS-related KS (AKS) and endemic KS (EKS) with regard to HHV-8 content as evaluated using polymerase chain reaction (PCR) and immunohistochemistry. DNA was extracted either using Chelex-100 or using Qia-gene kit and was evaluated with the help of a semiquantitative PCR assay. The PCR detection of HHV-8 was more sensitive to the Chelex method than to Qia-gene. The threshold for PCR test sensitivity with the help of serial dilution of DNA was at the level of five plasmid ORF-26 regions, and DNA from 25 body cavity-based lymphoma-1 cells. The results expressed as virus load/actin unit showed progressively higher HHV-8 levels in late (nodular) cases, compared to those in early (patch/plaque) stages. Evaluation of HHV-8 DNA levels in tumour tissues, thus, indicates a correlation between virus load and KS stage. Double immunostaining of spindle cells (SC) in KS biopsies for CD34 and HHV-8/latency-associated nuclear antigen (LANA) showed an increase in double-positive SC in the lesions of nodular AKS and EKS cases, compared to that in plaque and patch stages. However, 10-15% of CD34+/LANA- SC cells were observed during the development from patch to nodular cases of AKS and EKS. Our results indicate that PCR analysis is a simple and sensitive diagnostic method for HHV-8 evaluation in KS tissues, processed for conventional histopathology.