Kaposi sarcoma is a low-to-intermediate grade mesenchymal tumor that involves the lymphovascular system. The tumor can involve the pulmonary, gastrointestinal, cutaneous and musculoskeletal systems.
There are four recognized variants 1:
- classic (chronic): multiple distal lower extremity predominant purple skin plaques and rarely involve visceral organs
- endemic (lymphadenopathic): common in equatorial Africa
- iatrogenic (organ transplant-related)
- AIDS related (epidemic): usually requires the CD4 count to drop < 200 cells/mm3; may develop in up to 35% of patients with AIDS 2 and when developed it is considered an AIDS-defining illness
The latter two variants are much more common.
An etiological association with human herpes virus type 8 (HHV8) has been postulated. The AIDS-related and post-transplant variant are associated with immunosuppressive states.
Histologically can comprise of sheets of plump spindle-shaped cells surrounding and lining slit-like vascular spaces.
- lymphoproliferative disorders (particularly with the classic form)
There is a wide spectrum of imaging findings depending on which organ is involved. However, most features are nonspecific 1,2,4 but may assist in diagnosis if relevant clinical risk factors (e.g. background AIDS history) are evident. In 30% of cases, there is no concurrent cutaneous involvement 1.
The following features may be seen on chest radiographs:
- parenchymal nodular or reticular opacities with a predilection towards peri-hilar mid to lower zones; has two major patterns
- linear interstitial nodules
- fluffy ill-defined nodules
- pleural effusion(s)
- mediastinal and/or hilar lymphadenopathy
On HRCT of the chest:
- ill-defined (flame-shaped) nodular opacities with usually bilateral and roughly symmetrical perilymphatic and peribronchovascular distribution (1-2 mm)1
- may have surrounding patchy ground glass changes
- interlobular septal thickening
- lymphadenopathy (may be present in up to 50%) 5
- lymphadenopathy is typically of high attenuation 6
On liver CT:
- ill-defined multifocal peripheral portal nodules with variable attenuation (commonest hepatic neoplasm in AIDS patients) 1,4
Scintigraphy may be useful if concurrent opportunistic infection or lymphoma is suspected:
- Th201: usually positive in both lymphoma and Kaposi sarcoma
- Ga67: usually negative in Kaposi sarcoma but positive in lymphoma and infection
History and etymology
This condition was first described by Moritz Kaposi (1837-1902 an , Austro-Hungarian dermatologist in 1872.
For thoracic involvement consider
- 1. Restrepo CS, Martínez S, Lemos JA et-al. Imaging manifestations of Kaposi sarcoma. Radiographics. 26 (4): 1169-85. doi:10.1148/rg.264055129 - Pubmed citation
- 2. Davis SD, Henschke CI, Chamides BK et-al. Intrathoracic Kaposi sarcoma in AIDS patients: radiographic-pathologic correlation. Radiology. 1987;163 (2): 495-500. Radiology (abstract) - Pubmed citation
- 3. Witte MH, Fiala M, McNeill GC et-al. Lymphangioscintigraphy in AIDS-associated Kaposi sarcoma. AJR Am J Roentgenol. 1990;155 (2): 311-5. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Luburich P, Bru C, Ayuso MC et-al. Hepatic Kaposi sarcoma in AIDS: US and CT findings. Radiology. 1990;175 (1): 172-4. Radiology (abstract) - Pubmed citation
- 5. Hartman TE, Primack SL, Müller NL et-al. Diagnosis of thoracic complications in AIDS: accuracy of CT. AJR Am J Roentgenol. 1994;162 (3): 547-53. AJR Am J Roentgenol (abstract) - Pubmed citation
- 6. Herts BR, Megibow AJ, Birnbaum BA et-al. High-attenuation lymphadenopathy in AIDS patients: significance of findings at CT. Radiology. 1992;185 (3): 777-81. Radiology (abstract) - Pubmed citation
- 7. Kanne JP, Rohrmann CA, Lichtenstein JE. Eponyms in radiology of the digestive tract: historical perspectives and imaging appearances. Part 2. Liver, biliary system, pancreas, peritoneum, and systemic disease. Radiographics. 2006;26 (2): 465-80. doi:10.1148/rg.262055130 - Pubmed citation
- 8. Ganem D. KSHV and the pathogenesis of Kaposi sarcoma: listening to human biology and medicine. J. Clin. Invest. 2010;120 (4): 939-49. doi:10.1172/JCI40567 - Free text at pubmed - Pubmed citation