Kaposi sarcoma

Last revised by Ayla Al Kabbani on 18 Jun 2024

Kaposi sarcoma (KS) is a low-to-intermediate grade mesenchymal tumor that involves the lymphovascular system. The tumor can involve the pulmonary, gastrointestinal, cutaneous and musculoskeletal systems. Although it is often thought of as an AIDS-related condition, it may also be seen in other patient groups.

  • lymphoproliferative disorders (particularly with the classic form)

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.

Kaposi sarcoma is caused by infection with human herpesvirus-8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV) 9. 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.

There is a wide spectrum of imaging findings depending on which organ is involved. However, most features are non-specific 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 perihilar mid to lower zones; has two major patterns

    1. linear interstitial nodules

    2. 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 (typically >1 cm in diameter) 1

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:

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

  • gallium-67: usually negative in Kaposi sarcoma but positive in lymphoma and infection

This condition was first described by Moritz Kaposi (1837-1902), an Austro-Hungarian dermatologist, in 1872.

For thoracic involvement consider:

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