Immunohistochemical detection of the human herpes virus 8 (HHV8) latent nuclear antigen-1 in Kaposi's sarcoma

Kaposi Sarcoma in Afghanistan: A Case Series from a Tertiary Referral Center

Kaposi sarcoma is a vascular endothelial neoplasm caused by human herpesvirus 8. Although it is a well-studied disease, little is known about the specific characteristics or epidemiology of Kaposi sarcoma in Afghanistan. The data consist primarily of anecdotal reports and epidemiological studies extrapolated from neighboring countries. In this case series, we summarize existing data about Kaposi sarcoma in Afghanistan and present seven histologically confirmed cases with associated clinical features to shed light on the characteristics of Kaposi sarcoma in this unique geographic setting.

Immunohistochemical diagnosis of human infectious diseases: a review

BACKGROUND

Immunohistochemistry (IHC) using monoclonal and polyclonal antibodies is a useful diagnostic method for detecting pathogen antigens in fixed tissues, complementing the direct diagnosis of infectious diseases by PCR and culture on fresh tissues. It was first implemented in a seminal publication by Albert Coons in 1941.

MAIN BODY

Of 14,198 publications retrieved from the PubMed, Google, Google Scholar and Science Direct databases up to December 2021, 230 were selected for a review of IHC techniques, protocols and results. The methodological evolutions of IHC and its application to the diagnosis of infectious diseases, more specifically lice-borne diseases, sexually transmitted diseases and skin infections, were critically examined. A total of 59 different pathogens have been detected once in 22 different tissues and organs; and yet non-cultured, fastidious and intracellular pathogens accounted for the vast majority of pathogens detected by IHC. Auto-IHC, incorporating patient serum as the primary antibody, applied to diseased heart valves surgically collected from blood culture-negative endocarditis patients, detected unidentified Gram-positive cocci and microorganisms which were subsequently identified as Coxiella burnetii, Bartonella quintana, Bartonella henselae and Tropheryma whipplei. The application of IHC to ancient tissues dated between the ends of the Ptolemaic period to over 70 years ago, have also contributed to paleomicrobiology diagnoses.

CONCLUSION

IHC plays an important role in diagnostic of infectious diseases in tissue samples. Paleo-auto-IHC derived from auto-IHC, is under development for detecting non-identified pathogens from ancient specimens.

Kaposiform Hemangioendothelioma: clinicopathological characteristics of 8 cases of a rare vascular tumor and review of literature

BACKGROUND

Kaposiform Hemangioendothelioma (KHE) is a rare vascular tumor of intermediate malignant potential which shows locally aggressive growth but only rarely metastasizes. It is mostly considered to be a tumor of pediatric population but its occurrence in the adults is not uncommon as once considered. Histologically, KHE can mimic other soft tissue neoplasms of different behaviors (e.g. Kaposi Sarcoma, hemangioma) and establishing the correct diagnosis is important for appropriate treatment. Herein, we describe the clinicopathological features of 8 cases of KHE which will be helpful in making their diagnosis.

METHODS

We reviewed pathology reports, microscopy glass slides and obtained follow up information about 8 cases of KHE which were diagnosed at our institution from January 2008 till June 2020. Immunohistochemical stain for HHV8 was also performed.

RESULTS

Age ranged from 7 months to 25 years. Seven patients were less than 20 years of age and one patient was 25 years old. Equal gender distribution was observed. Extremities were the most common sites of involvement, followed by head and neck, pancreas and ischiorectal region. 2 cases were resection specimen and all others were incisional biopsies. The largest tumor size was 5.5 cm in one of the resections. The incisional/fragmented tissues were all less than 5 cm in aggregate. Most cases showed predominance of nodular growth and a minor component of spindle cell population along with lymphangiomatosis like vascular channels, with evidence of microthrombi in 2 cases. Few multinucleated giant cells were observed in 2 cases. None of the cases exhibited significant nuclear atypia or mitotic activity. One of the cases arising in dermis showed underlying bone involvement. HHV8 was negative in 7/7 cases.

CONCLUSIONS

KHE can also involve adult population and it should always be considered in the differential diagnoses of a vascular lesion. Presence of multinucleated giant cells is a rare finding. Knowledge about histological features and potential mimics is helpful in avoiding misdiagnosis.

Human oncoviruses: Mucocutaneous manifestations, pathogenesis, therapeutics, and prevention: Hepatitis viruses, human T-cell leukemia viruses, herpesviruses, and Epstein-Barr virus

In 1964, the first human oncovirus, Epstein-Barr virus, was identified in Burkitt lymphoma cells. Since then, 6 other human oncoviruses have been identified: human papillomavirus, Merkel cell polyomavirus, hepatitis B and C viruses, human T-cell lymphotropic virus-1, and human herpesvirus-8. These viruses are causally linked to 12% of all cancers, many of which have mucocutaneous manifestations. In addition, oncoviruses are associated with multiple benign mucocutaneous diseases. Research regarding the pathogenic mechanisms of oncoviruses and virus-specific treatment and prevention is rapidly evolving. Preventative vaccines for human papillomavirus and hepatitis B virus are already available. This review discusses the mucocutaneous manifestations, pathogenesis, diagnosis, treatment, and prevention of oncovirus-related diseases. The first article in this continuing medical education series focuses on diseases associated with human papillomavirus and Merkel cell polyomavirus, while the second article in the series focuses on diseases associated with hepatitis B and C viruses, human T-cell lymphotropic virus-1, human herpesvirus-8, and Epstein-Barr virus.

Diagnosis and Treatment of Kaposi Sarcoma

Kaposi sarcoma (KS) is the most common neoplasm of people living with HIV today. In Sub-Saharan Africa, KS is among the most common cancers in men, overall. Not only HIV-positive individuals present with KS; any immune compromised person infected with KS-associated herpesvirus (KSHV) or human herpesvirus 8 is at risk: the elderly, children in KSHV-endemic areas, and transplant recipients. KS diagnosis is based on detection of the viral protein latency-associated nuclear antigen (LANA) in the biopsy, but not all cases of KS are the same or will respond to the same therapy. Standard KS therapy has not changed in 20 years, but newer modalities are on the horizon and will be discussed.

mTOR, VEGF, PDGFR, and c-kit signaling pathway activation in Kaposi sarcoma

Kaposi sarcoma (KS) is a locally progressive, intermediate-grade vascular neoplasm with no known cure, high recurrence rates, and potential for wide dissemination. Low efficacy and high toxicity limit current therapeutic options for advanced disease. Activation of mammalian target of rapamycin (mTOR), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and c-kit signaling pathways has been implicated in KS pathogenesis and may suggest a role for targeted inhibitors. KS cases were retrospectively retrieved (N=274), most (90%) associated with human immunodeficiency virus. Tissue microarray slides were stained with human herpes virus-8, Friend leukemia integration 1 transcription factor, CD117 (c-kit), phospho-S6 (pS6), PDGF receptor-β, VEGF, and phospho-mTOR. Both intensity and extent of staining were scored. Multiplying these scores for each core yielded total staining H-scores. Human herpes virus-8 was positive in 87% and Friend leukemia integration 1 transcription factor in 95.7% of cases. Most were also VEGF+ (97.6%), pS6+ (95.7%), CD117+ (92.5%), and PDGFRB+ (87.4%). Approximately half (55.6%) were phospho-mTOR+. There was no significant difference in staining among patients with low (<500 cells/mm³) or preserved CD4 T-cell counts. Immunohistochemistry confirms upregulation of the mTOR, PDGF, VEGF, and c-kit pathways in a large cohort of KS samples. Of proteins tested, pS6, downstream of mTOR, demonstrated the highest proportion of strong positivity (67.1%). These results support the possibility of using targeted inhibitors in KS. Overexpression was independent of CD4 count, suggesting that even patients with low counts may be targeted therapy candidates.

Variability of HHV8 LNA-1 Immunohistochemical Staining Across the 3 Histologic Stages of HIV-Associated Mucocutaneous Kaposi Sarcoma: Is There a Relationship to Patients' CD4 Counts?

The histologic diagnosis of Kaposi sarcoma (KS) can be confirmed with human herpes virus 8 (HHV8) latency-associated nuclear antigen (LNA)-1 immunohistochemistry, which may show variability in distribution and intensity. This retrospective study was aimed at addressing the factors that may contribute to this variability. All cases of mucocutaneous KS diagnosed in a 5-year period at the histopathology department at a tertiary hospital in South Africa with available patients' CD4 counts and HHV8 LNA-1 immunohistochemically stained slides were reviewed, and the biopsy stages of KS (patch/plaque/nodular), CD4 counts, immunohistochemistry staining method (manual vs. automated), and distribution (diffuse/focal) and intensity (strong/weak) of HHV8 LNA-1 staining were recorded. A total of 127 cases were reviewed. No relationship was demonstrated between the median CD4 count and the histologic stages of KS (P = 0.701) or the intensity and distribution of HHV8 immunohistochemical staining using either staining method. Multivariate analysis showed that method of immunohistochemical staining was a significant predictor of distribution (P = 0.006) and intensity (P = 0.044) of staining, and that stage was a significant predictor of distribution of staining (P = 0.033).

Accuracy of Clinical Suspicion and Pathologic Diagnosis of Kaposi Sarcoma in East Africa

BACKGROUND

HIV-associated Kaposi sarcoma (KS) is one of the most common malignancies in sub-Saharan Africa. The diagnosis is often based on clinical suspicion, without histopathologic confirmation. When biopsies are performed, the accuracy of interpretation by local pathologists is poorly understood. We assessed the accuracy of clinical suspicion and pathologic diagnosis of KS in 2 East African countries.

METHODS

At 2 large HIV care sites in Uganda and Kenya, we evaluated consecutive biopsies performed from October 2008 to January 2013 on HIV-infected adults with clinically suspected KS. Biopsies were interpreted by both local African pathologists and a group of US-based dermatopathologists from a high volume medical center. For the purpose of this analysis, the US-based dermatopathologist interpretation was used as the gold standard. Positive predictive value was used to characterize accuracy of local African clinical suspicion of KS, and concordance, sensitivity, and specificity were used to characterize accuracy of local pathologic diagnosis.

RESULTS

Among 1106 biopsies, the positive predictive value of clinical suspicion of KS was 77% (95% confidence interval: 74% to 79%). When KS was not histopathologically diagnosed, clinically banal conditions were found in 35%, medically significant disorders which required different therapy in 59% and life-threatening diseases in 6%. Concordance between African pathologists and US-based dermatopathologists was 69% (95% confidence interval: 66% to 72%). Sensitivity and specificity of African pathologic diagnoses were 68% and 89%, respectively.

CONCLUSIONS

Among East African HIV-infected patients, we found suboptimal positive predictive value of clinical suspicion of KS and specific, but not sensitive, histopathologic interpretation. The findings call for abandonment of isolated clinical diagnosis of KS in the region and augmentation of local dermatopathologic services.

Upper gastrointestinal Kaposi's sarcoma in HIV-infected patients: ten years of endoscopy observation at a single Brazilian center

BACKGROUND

Kaposi's sarcoma (KS) is the most common neoplasm among HIV-infected individuals. The frequency of involvement of KS in the gastrointestinal (GI) tract and the associated epidemiological, immune, endoscopic, and histopathological features in HIV-infected patients, were evaluated in this study.

METHODS

A review of the medical and endoscopy reports of 1428 HIV-infected patients, who had undergone upper GI endoscopy at the Endoscopy Service, Clinical Hospital, Faculty of Medicine of Ribeirão Preto between January 1999 and June 2009, was performed. Clinical, epidemiological, immunological, endoscopic, and histological data were collected.

RESULTS

Twenty-seven (1.9%) patients were diagnosed with GI KS. Patients were predominantly male (81.5%). Sexual activity was the main route of HIV transmission (81.5%). Cutaneous involvement was noted in 21 patients (78%). Fifteen patients (55%) received highly active antiretroviral therapy for a mean duration of 12.6 weeks (range 2-52 weeks) before endoscopy. GI lesions were mainly found in the stomach (55%). Analysis of the immunohistochemical methods HHV8 LNA-1, CD31, and CD34 for the diagnosis of gastric KS indicated high agreement (kappa=0.63, 95% confidence interval 0.32-0.94). There was no relationship between CD4 levels (p=0.34) or HIV viral load (p=0.99) and HHV8 LNA-1 positivity in gastric KS.

CONCLUSIONS

GI KS is an infrequent finding in patients with HIV infection. Among those with GI KS, 80% had concomitant skin lesions. Immunohistochemical methods for CD31, CD34, and LNA-1 were important tools in the diagnostic assessment of lesions suggestive of KS in the GI tract. Further studies are required to confirm these data, and the need for routine endoscopic investigation of the GI tract in HIV-infected patients with cutaneous KS should be assessed.

The Utility of Immunohistochemistry for Providing Genetic Information on Tumors

With advances in immunohistochemical technology and growing knowledge of the molecular genetics of tumors, immunohistochemistry is playing an increasingly important role in providing genetic information for tumors. Specific chromosomal translocations can be demonstrated through detection of the protein product of one of the genes involved in gene fusion (such as BCL2, cyclin D, and ALK). Some mutations can be detected by (1) aberrant localization of the protein product (such as β-catenin and nucleophosmin), (2) abnormal accumulation of the protein product as a result of stabilization of the protein (such as p53), and (3) mutation-specific antibodies directed against the mutant protein (such as isocitrate dehydrogenase gene R132H mutation, epidermal growth factor receptor gene L858R and exon 19 deletion mutations, and BRAF gene V600E mutation). Gene deletion or loss of function can be demonstrated by the loss of immunostaining for the protein product (such as mismatch repair proteins in microsatellite-unstable tumors, E-cadherin in lobular carcinoma of the breast, and INI1 in rhabdoid tumors, atypical teratoid/rhabdoid tumors, and epithelioid sarcomas). Gene amplification can be demonstrated by overexpression of the protein product (such as HER2 in breast and gastric cancers, and MDM2 or CDK4 in well-differentiated/dedifferentiated liposarcomas). Viruses associated with tumors can be demonstrated directly (such as Epstein-Barr virus latent membrane protein-1 in Hodgkin lymphomas, human herpesvirus 8 in Kaposi sarcomas, and Merkel cell polyomavirus in Merkel cell carcinomas) or by a surrogate marker (such as p16 in human papillomavirus infection). In this review, examples are given to illustrate the principles and pitfalls of these applications.

Diagnostic value of endothelial markers and HHV-8 staining in gastrointestinal Kaposi sarcoma and its difference in endoscopic tumor staging

AIM: To clarify the diagnostic values of hematoxylin and eosin (HE), D2-40, CD31, CD34, and HHV-8 immunohistochemical (IHC) staining in gastrointestinal Kaposi’s sarcoma (GI-KS) in relation to endoscopic tumor staging.

METHODS: Biopsy samples (n = 133) from 41 human immunodeficiency virus-infected patients were reviewed. GI-KS was defined as histologically negative for other GI diseases and as a positive clinical response to KS therapy. The receiver operating characteristic area under the curve (ROC-AUC) was compared in relation to lesion size, GI location, and macroscopic appearances on endoscopy.

RESULTS: GI-KS was confirmed in 84 lesions (81.6%). Other endoscopic findings were polyps (n = 9), inflammation (n = 4), malignant lymphoma (n = 4), and condyloma (n = 2), which mimicked GI-KS on endoscopy. ROC-AUC of HE, D2-40, blood vessel markers, and HHV-8 showed results of 0.83, 0.89, 0.80, and 0.82, respectively. For IHC staining, the ROC-AUC of D2-40 was significantly higher (P < 0.05) than that of HE staining only. In the analysis of endoscopic appearance, the ROC-AUC of HE and IHC showed a tendency toward an increase in tumor staging (e.g., small to large, patches, and polypoid to SMT appearance). D2-40 was significantly (P < 0.05) advantageous in the upper GI tract and for polypoid appearance compared with HE staining.

CONCLUSION: The diagnostic value of endothelial markers and HHV-8 staining was found to be high, and its accuracy tended to increase with endoscopic tumor staging. D2-40 will be useful for complementing HE staining in the diagnosis of GI-KS, especially in the upper GI tract and for polypoid appearance.

Utility of immunohistochemical staining with FLI1, D2-40, CD31, and CD34 in the diagnosis of acquired immunodeficiency syndrome-related and non-acquired immunodeficiency syndrome-related Kaposi sarcoma

CONTEXT

Kaposi sarcoma (KS) is a vascular tumor frequently associated with advanced human immunodeficiency virus infection, advanced age, or iatrogenic immunosuppression. Immunohistochemistry for CD31 and CD34, and more recently for FLI1 and D2-40, has been used as ancillary diagnostic tests for KS, despite little information regarding the sensitivities and differential staining patterns of the latter 2 markers in the major clinical subtypes and histologic stages of KS.

OBJECTIVE

This retrospective study aims to assess the prevalence of the vascular markers D2-40 and FLI1 in the main clinical subgroups and tumor stages of KS.

DESIGN

Twenty-four cases of KS (12 acquired immunodeficiency syndrome [AIDS]-related cases and 12 non-AIDS-related cases; 11 nodular-stage and 13 patch/plaque-stage KS) were stained for CD34, CD31, D2-40, and FLI1 by immunohistochemistry. The distribution of immunoreactivity was compared between the clinical subtypes and tumor stages of KS using the Mann-Whitney test.

RESULTS

CD31, CD34, D2-40, and FLI1 strongly and diffusely stained tumor cells in 75%, 92%, 67%, and 92% of AIDS-related cases and 58%, 92%, 67%, and 75% of non-AIDS-related cases, respectively. Differences in the proportions of positive cases between AIDS-related and non-AIDS-related cases did not reach statistical significance. No significant staining differences were observed between nodular- and patch/plaque-stage KS either.

CONCLUSIONS

There are no differences in the distribution of immunohistochemical reactivity for CD31, CD34, D2-40, or FLI1 between AIDS-related and non-AIDS-related KS or between nodular- and patch/plaque-stage KS. All of the markers studied demonstrated high sensitivity in both clinical settings and both stages of tumor progression.

Evaluation of c-kit expression in classic Kaposi's sarcoma in a cohort of Egyptian patients

BACKGROUND

Kaposi's sarcoma (KS) is an angioproliferative disorder associated with human herpesvirus 8 infection. Classic KS is the most prevalent type of KS in countries of the Mediterranean basin including Egypt. Several in vitro studies have detected c-kit expression in AIDS related-KS however, only a few studies addressed this issue in the classic type with no data on the ethnicity of studied cases. The prospect of installing targeted anti- c-kit treatment to KS patients presents a promising avenue in KS therapeutics.

AIM

To elucidate the expression of c-kit in classic KS cases and study possible relations with expression of HHV8 latency-associated nuclear antigen-1 (LANA-1) and other clinicopathological parameters.

METHODS

Twenty four cases of classic KS of the plaque and nodular stages in the lower limb were studied. Immunohistochemical detection of HHV8-LANA-1 and c-kit was carried out on archival paraffin embedded tissue, possession of the Pathology and Dermatology Departments, Alexandria School Of Medicine, Egypt. Statistical analysis of possible relations between both antigens and clinicopathological parameters (patient's age and gender and histological stage) was performed.

RESULTS

HHV8 expression was detected in 100% of cases while c-kit immunoreactivity was found in 54.2% of cases. There was no correlation between c-kit and HHV8 immunoreactivity or any of the studied clinicopathological parameters.

CONCLUSIONS

This is the first report of c-kit expression in classic KS in an ethnically homogeneous cohort of Arabs of the Mediterranean region. We detected c-kit expression in about half the cases with no relationship to HHV8 LANA expression or clinicopathological parameters.

Selected Pseudoneoplastic Lesions of the Skin

Context.—Pseudoneoplastic cutaneous lesions are diverse, not only morphologically but also with respect to their causes and cellular lineages. They include proliferations of epithelial, as well as mesenchymal, elements.

Objective.—This review aims to consider selected lesions in the aforementioned groups, contrasting them with histologically similar neoplasms of the skin in a differential diagnostic setting.

Data Sources.—Information used in assembling this discussion was drawn from the published literature on cutaneous pseudoneoplasms, using an Internet-based search engine. The authors' collective experience was also used in writing this review.

Conclusions.—Sufficient clinical and morphologic differences exist in virtually all instances to separate pseudoneoplastic cutaneous proliferations from the tumors that they imitate.

Immunohistochemistry in Kaposi's sarcoma

The importance of immunohistochemistry (IHC) to our understanding, ability to confidently diagnose and treat Kaposi's sarcoma (KS) has grown steadily in the past few decades. IHC has been performed on many KS specimen types, with > 100 different primary antibodies. Therefore, it is not surprising that IHC has helped unravel the histogenesis, understand the pathogenesis and facilitate the diagnosis of KS and identify novel therapeutic targets in the disease. This paper reviews the literature on the use of IHC in the study of KS.

Kaposi sarcoma: a continuing conundrum

Kaposi sarcoma (KS) remains a challenge. Its classic or Mediterranean form tends to be benign. In transplant recipients it may be less so. As part of the AIDS pandemic, of which it was an original defining component, it may be life-threatening. It is due to human herpesvirus-8, which is necessary but not sufficient to produce the disease. KS has a low prevalence in the general population of the United States and United Kingdom, with an intermediate rate in Italy and Greece, and a high one in parts of Africa. In Italy, hot spots include its southern regions, the Po River Valley, and Sardinia, possibly related to a high density of blood-sucking insects. An important challenge is to treat KS patients without immunocompromising them. The potential of effective anti-herpes virus therapy and the use of sirolimus in transplantation recipients have added new opportunities for KS prevention.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be able to provide the most recent information about Kaposi sarcoma in the context in which it occurs. Its classic or Mediterranean form, its pattern in transplant recipients and others iatrogenically immunosuppressed, and its occurrence as a potentially life-threatening part of the AIDS pandemic will be stressed. Its etiology and transmission will be discussed in detail to facilitate understanding of Kaposi sarcoma and of human herpesvirus-8 infection in the general population of the United States and United Kingdom, in Italy and Greece, and in certain parts of Africa. Its therapy, including the concept of doing it without immunocompromising the patient, will be stressed. New opportunities for Kaposi sarcoma prevention will also be discussed.

Kaposi’s sarcoma in Morocco: a pathological study with immunostaining for human herpesvirus-8 LNA-1

AIMS

The Maghreb region is considered to be an endemic area for classical Kaposi's sarcoma (KS) but the few published reports have focused on clinical descriptions. We report here the clinical, virological and pathological features of 26 KS cases, including 17 classic forms, eight epidemic forms and one case of post-transplant KS.

METHODS

Evidence of human herpesvirus (HHV)-8 infection was detected by serology, immunohistochemistry and polymerase chain reaction.

RESULTS

Antibodies directed against HHV-8 latent nuclear antigen (LNA-1/ORF73) were present in sera from all 26 KS cases and the ORF26 HHV-8 gene fragment was amplified from the tumour DNA of all patients. KS lesions that met the classical criteria for KS (spindle cells, positive endothelial markers) and were immunostained with the anti-LNA-1 marker, demonstrated typical granular intranuclear labelling of the spindle cells in all but one case of KS, in which very few spindle cells were present. Furthermore, whereas LNA-1 staining was largely confined to spindle cells in the late nodular stage, it was also observed in endothelial cells forming the walls of slit-like vessels in early patch-stage lesions.

CONCLUSION

This study confirms that Morocco is an endemic area for classical KS, which remains the most frequent type of KS in this country, and emphasises the value of the LNA-1 marker for the early diagnosis of KS lesions.

Human herpesvirus 8 and angiosarcoma: analysis of 40 cases and review of the literature

AIMS

To prove a possible involvement of the endotheliotropic human herpesvirus 8 (HHV-8) in the pathogenesis of angiosarcoma in samples from patients in a low HHV-8 seroprevalence area.

METHODS

A comprehensive series of angiosarcomas (n = 40) as well as positive and negative control tissues from patients with Kaposi's sarcoma, human immunodeficiency virus (HIV)-associated multicentric Castleman's disease or juvenile haemangioma, respectively, was analysed with two sensitive methods: immunohistochemical staining for the HHV-8 latency-associated nuclear antigen 1 (LANA-1); and polymerase chain reaction (PCR) for HHV-8 VP23 DNA sequences.

RESULTS

None of the angiosarcoma cases and none of the negative control samples (juvenile haemangiomas) revealed positive immunohistochemical staining with the LANA-1 antibody. In contrast, HHV-8 LANA-1 was clearly detected in all analysed cases of Kaposi's sarcoma and multicentric Castleman's disease. These results were confirmed by PCR assay at the DNA level.

CONCLUSION

In conclusion, the great majority of angiosarcomas investigated to date, including the series of 40 angiosarcomas analysed here, does not contain HHV-8 DNA sequences or protein. This argues against a relevant role of the endotheliotropic HHV-8 in the pathogenesis of angiosarcoma and, for vascular diseases, speaks in favour of a relatively restricted pathogenic role of HHV-8 to Kaposi's sarcoma and multicentric Castleman's disease.

Advances in the pathobiology and treatment of Kaposi sarcoma

PURPOSE OF REVIEW

Kaposi sarcoma, which has reached epidemic proportions in parts of Africa and in the Western world, continues to pose a problem in patients with AIDS receiving highly active antiretroviral therapy (HAART). This article reviews the new and important information regarding the epidemiology, biology, and management of Kaposi sarcoma that was published in the last year.

RECENT FINDINGS

Worldwide Kaposi sarcoma herpesvirus/human herpesvirus 8 (HHV8) seropositivity has been found to exceed the incidence of Kaposi sarcoma. Therefore, investigators have justifiably implicated other cofactors (eg, blood-sucking arthropods, angiotensin converting enzyme inhibitors, hemodialysis, and iron) in the development of Kaposi sarcoma. In the transplant setting, Kaposi sarcoma lesions have been shown to originate from the engraftment of donor tumor cells. The detection of HHV8 in Kaposi sarcoma lesions has provided a new diagnostic tool to help differentiate Kaposi sarcoma from its mimics. Kaposi sarcoma lesional cells, now confirmed to be of lymphatic origin, have been shown to express several chemokine receptors, some of which may help explain the predilection for skin. Regression of Kaposi sarcoma has been characterized histologically for the first time. The finding that some tumor cells can remain in an atrophic state even in completely regressed lesions suggests that they have the potential to recur. Protease inhibitor-based and nonnucleoside reverse transcriptase inhibitor-based HAART regimens have been verified to be similarly effective. Although antiretrovirals have been noted to favorably alter the clinical characteristics of Kaposi sarcoma favorably, they seem not to alter the natural history of this disease. In the HAART era, because CD4 cell count was shown no longer to provide prognostic information about AIDS-related Kaposi sarcoma, the traditional classification system for staging AIDS-related Kaposi sarcoma has been refined. Also, a new staging system for classic Kaposi sarcoma has been proposed.

SUMMARY

Numerous advances have emerged regarding Kaposi sarcoma during the last year, many of which still need to be translated into clinically useful information. The results of new clinical trials involving antivirals purposely directed against HHV8 and antiretrovirals for HIV-uninfected people are anticipated. Finally, although investigators during this period did provide us with additional potential therapeutic targets, more novel approaches such as RNA interference and gene therapy have been also proposed as options in the future management of Kaposi sarcoma.