You are in: eMedicine Specialties > Radiology > CHEST Kaposi Sarcoma, ThoracicArticle Last Updated: May 30, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Klaus L Irion, MD, PhD, Consulting Staff, The Cardiothoracic Centre Liverpool NHS Trust, The Royal Liverpool University Hospital, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Alberto Alonso, MD, MRCP, Specialist Registrar in Radiology, Department of Radiology, Manchester Royal Infirmary, UK; Carolyn M Allen, MB, BCh, MRCP, FRCR, CCST, Consultant Radiologist, Department of Clinical Radiology, North Manchester General Hospital, UK Editors: Satinder P Singh, MD, Associate Professor of Radiology, Chief of Cardiopulmonary Radiology, Director of Cardiac CT, Director of Combined Cardiopulmonary and Abdominal Radiology, Department of Radiology, University of Alabama at Birmingham; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Eric J Stern, MD, Professor of Radiology, Adjunct Professor of Medicine, Adjunct Professor of Medical Education and Biomedical Informatics, University of Washington School of Medicine; Director of Thoracic Imaging, Harborview Medical Center; Associate Medical Staff, Seattle Cancer Care Alliance; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Clinical Assistant Professor of Radiology, University of Washington Medical School Author and Editor Disclosure Synonyms and related keywords: KS, Kaposi's sarcoma, thoracic Kaposi's sarcoma, acquired immunodeficiency syndrome, AIDS, human immunodeficiency virus, HIV, human herpesvirus 8, HHV-8, Kaposi sarcoma herpesvirus, KSHV INTRODUCTIONSection 2 of 11
  BackgroundMoritz Kaposi first described Kaposi sarcoma (KS) in 1872. Although the disease was described initially in elderly men of Mediterranean extraction, KS is currently widely recognized as the most common malignancy associated with acquired immunodeficiency syndrome (AIDS). Originally, the disease was believed to be a form of primary skin cancer; however, a viral etiology now has been firmly established.1, 2, 3 PathophysiologyA virus belonging to the herpes family (human herpesvirus 8 [HHV-8], also called Kaposi sarcoma herpesvirus [KSHV]), has been identified as the probable cause of KS. This virus likely acts in conjunction with other cofactors. KSHV serology always demonstrates positive results in affected individuals, regardless of immune status, and the presence of antibodies is predictive of KS and has prognostic value. KSHV DNA is present in the lymphoid system, peripheral blood mononuclear cells, saliva, and semen of patients with KS. In AIDS, KS is a polyclonal neoplasm with distinct pathologic features. In the very early stages, KS is characterized by inflammatory cell infiltration, extravasation of red blood cells, endothelial cell activation, and angiogenesis. After activation, endothelial cells acquire the appearance of typical spindle-shaped cells mixed with macrophages and dendritic cells. In advanced disease, spindle cells tend to become the predominant cell type, although angiogenesis remains a prominent feature. KS affects mucocutaneous tissues, particularly involving the trunk and lower limbs, as well as the thoracic cavity and gastrointestinal (GI) system. Histologic appearances are identical irrespective of the organ of involvement. Thoracic KS may involve the upper airways, the pulmonary parenchyma, or the pleura. However, the upper airways are rarely affected in patients with pulmonary KS. Classic violaceous endobronchial plaques may be seen bronchoscopically; typically, the lesions are located at airway bifurcations. Pleural effusions, which are frequently bloody and often large, occur in 15-89% of patients with pulmonary KS. Typically, these effusions are exudates and often contain reactive mesothelial cells without evidence of neoplasm. Macroscopically, flat or slightly raised, disk-shaped, red or violaceous plaques confined to the visceral pleura are seen. Pulmonary parenchymal changes include lymphangitic infiltration by tumor, causing nodular thickening and red-blue discoloration of interlobular septa and the peribronchovascular interstitium. The nodules may coalesce to form larger masses.4, 5, 6 FrequencyUnited StatesBy far, KS is the most common AIDS-related malignancy, affecting approximately 25% of patients with AIDS overall and 50% of cohorts of homosexual men who have HIV infection. Data collected by the US Centers for Disease Control and Prevention reveal that the incidence of KS has declined by an estimated 10% per year between 1990 and 1997. Furthermore, the number of homosexual patients with AIDS who have KS as an AIDS-defining illness has decreased from 40% in the early 1980s to 10-20%. This decline likely reflects a change in the demographics of AIDS: because of the use of safe sex practices, there has been a decrease in the number of patients within specific high-risk categories; there has been a relative increase in heterosexual and vertical transmission; and there has been a relative increase in the transmission of HIV via contaminated needles. The use of antiretroviral therapy is associated with a reduction in the risk of the development of KS, ranging from a 13% reduction with monotherapy or dual therapy to a 59% reduction with triple therapy. Although the incidence of KS is falling in the United States, in impoverished countries, the incidence is likely to continue to rise. Postmortem studies of individuals with AIDS with cutaneous KS reveal pulmonary involvement in 47-75% of patients, although as many as two thirds of cases may not be clinically evident. In 2000, pulmonary KS was reported in 20,000 cases in the United States. InternationalIatrogenic KS occurs in approximately 6% of male European, Jewish, or African patients after solid-organ transplantation. The incidence of KS after renal transplantation in these patients is 500 times greater than in other populations. In Africa, endemic KS affects young people of either sex and of any sexual orientation.7 Mortality/MorbidityStudies of KS by the AIDS Clinical Trial Group (ACTG) show that pulmonary involvement is not associated with diminished survival among patients with extensive KS. Poor prognostic factors for survival among patients with thoracic KS in non-ACTG clinical trials have included the following:
Patients with KS and a CD4+ T cell count of more than 150 cells/µL had a median survival of 39 months, whereas patients with fewer than 150 cells/µL survived a median of only 12 months (P <0.001). Considerable progress has been made in the treatment of KS with the development of liposomal anthracycline therapy, paclitaxel-based regimens, and newer agents such as retinoids and antiangiogenic drugs, although the prognosis remains generally poor. The course of pulmonary KS is variable; it may be either slowly progressive or aggressive. RaceAIDS-related KS does not show any racial predominance, although more patients are black than white; the highest incidence is seen in Africa. Endemic Kaposi sarcoma affects young people in Africa of either sex and of any sexual orientation. SexKS is seen almost exclusively in homosexual or bisexual men with HIV infection or in their partners. The male-to-female ratio is 50:1. KS is 20 times more prevalent among homosexual men with HIV infection than among heterosexual patients with hemophilia and HIV infection or among patients of either sex who abuse intravenous drugs. Endemic KS affects young people in Africa of either sex or any sexual orientation. In the United States, the prevalence of people having serum antibodies to HHV-8 is 1% in the general blood-donor population, 35% in homosexual men with HIV infection, and 4% in women with HIV infection. Correspondingly, KS develops in 20-30% of homosexual or bisexual men with HIV infection and in only 1% of women with HIV infection. AgeKS is usually a disease of adults. Clinical DetailsUsually, mucocutaneous lesions are the first clinical sign of KS. Lesions usually measure 1-2 cm in diameter and are raised, violaceous, and plaquelike. They may appear brown or black in patients with dark skin. Lesions increase in size and number as the disease progresses. Involvement of the GI tract, lymph nodes, lungs, and other viscera is common. Pulmonary involvement occurs in one third of patients and is recognized clinically in 10-15% of patients. Symptoms such as breathlessness, cough, fever, and wheezing are nonspecific. Hemoptysis may occur but is unusual. Although lung involvement invariably follows mucocutaneous disease, this may not be clinically apparent. KS usually affects patients with CD4+ T cell counts of less than 100 cells/µL. The tumor tends to run an aggressive course, becoming more aggressive with increasing immunocompromise. Healthy patients who demonstrate positive results with HIV/KSHV serologic testing have been shown to develop clinical manifestations when the CD4+ T cell count falls. To define the natural history of AIDS-related KS, various staging systems have been proposed.8 In the United States, the schema originally developed by the ACTG Committee on Malignancies has been used the most. It classifies patients into good-risk or poor-risk groups on the basis of 3 main factors, as follows:
A change in the CD4+ T cell count from 200 to 150 cells/µL is the only modification needed to best distinguish between good-risk and poor-risk immune system categories. Revised AIDS Clinical Trial Group Staging Classification for KS*
*Adapted from Krown et al.9 Preferred ExaminationA chest radiograph is usually the initial examination in patients in whom KS is suggested because radiographic appearances of pulmonary KS are among the most distinctive seen in patients with AIDS; even subtle abnormalities should be viewed as suggestive of pulmonary involvement in a patient with known mucocutaneous disease. An accurate diagnosis of pulmonary KS can be established by using CT scanning in 90% of patients. The role of MRI in the diagnosis of KS has not been defined. Ultrasonography of the thorax is useful in the evaluation of pleural disease and for guiding therapeutic thoracentesis. Radionuclide imaging is a useful adjunct to radiography and CT in selected patients; it is not always possible to differentiate KS from opportunistic infections by using anatomic imaging.10, 11, 12, 13, 14 Limitations of TechniquesA wide variety of pulmonary complications may occur in patients who are immunocompromised, including opportunistic infections, drug-induced lung disease, malignancy, and unrelated pathologic processes such as pulmonary edema and pulmonary embolism. These disorders may have similar radiographic appearances (see Differentials, below). DIFFERENTIALSSection 3 of 11
Lung, Nontuberculous Mycobacterial Infections Lung, Postprimary Tuberculosis Lung, Primary Tuberculosis Lymphangitic Carcinomatosis Other Problems to Be ConsideredDifferential diagnosis of pulmonary nodules in AIDS Infections — Bacterial infection, septic emboli, infection with Mycobacterium tuberculosis and Mycobacterium avium-intracellulare, fungal infection, viral infection, and toxoplasmosis Malignancy — KS, AIDS-related lymphoma, and lung carcinoma Differential diagnosis of lymphadenopathy in AIDS Infections — Tuberculosis, infection by M avium-intracellulare, fungal infection, and Pneumocystis jiroveci pneumonia (PCP) Malignancy — AIDS-related lymphoma, KS, and lung carcinoma RADIOGRAPHSection 4 of 11
Findings
Degree of ConfidenceRadiographic appearances of pulmonary KS are among the most distinctive seen in patients with AIDS; even subtle abnormalities should be viewed as suggestive of pulmonary involvement in a patient with known mucocutaneous disease. False Positives/NegativesSee Differentials. CT SCANSection 5 of 11
Findings
Degree of ConfidenceAmong AIDS-related thoracic diseases, KS is one of the most reliable diagnoses made on the basis of imaging findings. An accurate diagnosis of pulmonary KS can be established by CT scans in 90% of patients.15, 16, 17 False Positives/NegativesSee Differentials. MRISection 6 of 11
FindingsThere is little evidence that MRI is as useful as other methods in diagnosing pulmonary KS. Although MRI is an excellent modality for detection of thoracic wall involvement, it is not useful in intrathoracic lesions apart from, perhaps, imaging large-vessel involvement.18
ULTRASOUNDSection 7 of 11
FindingsUltrasonography of the thorax is useful in the evaluation of pleural disease and for guiding therapeutic thoracentesis. NUCLEAR MEDICINESection 8 of 11
FindingsApproximately two thirds of patients with KS presenting with new pulmonary abnormalities have coexistent opportunistic infections. Differentiating KS from opportunistic infections is not always possible by using anatomic imaging. Gallium-67/thallium-201 (67Ga/201Tl) radionuclide imaging has been used to distinguish AIDS-related KS from other pulmonary disease processes. KS is 201Tl avid, but it does not take up 67Ga. Abnormal chest radiographic findings in association with negative 67Ga findings suggest the presence of pulmonary KS. Indium-111–labeled polyclonal immunoglobulin is taken up by infection but not by KS or lymphoma. Indium-labeled liposomes have been shown to accumulate in KS, but uptake has also been reported with lymphoma.19 Degree of ConfidenceRadionuclide scans are a useful adjunct to radiographs and CT scans, particularly when radiographic findings are complex and when the exclusion of opportunistic infections that complicate KS is important. Indium-11-labeled polyclonal immunoglobulin uptake has a sensitivity of 97% in the diagnosis of AIDS-related pulmonary infections; by contrast, chest radiography has a sensitivity of 62%. Although high-resolution computed tomography (HRCT) is superior to chest radiography, some have suggested that HRCT may be less sensitive than 67Ga scintigraphy in the assessment of suspected Pneumocystis jiroveci pneumonia (PCP). False Positives/NegativesA false-positive rate of 15% has been reported with gallium scanning in the assessment for Pneumocystis jiroveci pneumonia (PCP). Other infections and lymphomas may also take up gallium. It has been suggested that thallium uptake may occur in lymphoma and infections such as PCP. INTERVENTIONSection 9 of 11
Although KS lesions may be safely examined at biopsy, biopsy is rarely needed because the diagnosis can be reliably made on the basis of characteristic clinical, bronchoscopic, and radiographic findings. For AIDS patients who have abnormal chest radiographs and whose bronchoscopy findings are nondiagnostic, CT-guided percutaneous needle aspiration biopsy (PCNA) or percutaneous core biopsy (PCB) may increase the diagnostic yield. Although PCNA and PCB have a yield of approximately 85% in patients with AIDS, KS is difficult to diagnose. Multiple core biopsies may increase the yield in patients with KS in whom a biopsy is needed because of atypical clinical or radiographic features and in whom the need to exclude coexistent infection is paramount. With both PCNA and PCB, the diagnostic yield is poor with KS; therefore, multiple core biopsies are performed. Complications from PCB are the same as in patients without AIDS and include a pneumothorax, hemoptysis, hemothorax, and accidental puncture of major vessels. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Kaposi Sarcoma, Thoracic excerpt Article Last Updated: May 30, 2008 | ||||||||||||||||||||||||||||||||||||||||
