Kaposi sarcoma

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 :

  • 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/mm; may develop in up to 35% of patients with AIDS  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 variants are also 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)

Radiographic features

There is a wide spectrum of imaging findings depending on which organ is involved. However, most features are non-specific 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 .

Plain radiograph

The following features may be seen on chest radiographs:

  • parenchymal nodular or reticular opacities with a predilection towards perihilar 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:

On liver CT:

  • ill-defined multifocal peripheral portal nodules with variable attenuation (commonest hepatic neoplasm in AIDS patients) 
Nuclear medicine

Scintigraphy may be useful if concurrent opportunistic infection or lymphoma is suspected:

  • thallium-201: usually positive in both lymphoma and Kaposi sarcoma
  • gallium-67: 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.

Differential diagnosis

For thoracic involvement consider:

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