Mesenchymal tumors

Kaposi sarcoma

Last author update: 4 March 2021
Last staff update: 3 May 2022

Copyright: 2003-2023,, Inc.

PubMed Search: Kaposi sarcoma[TIAB] colon

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Kaposi sarcoma. website. Accessed February 1st, 2023.
Definition / general
  • Vascular malignancy caused by human herpes virus 8 (see topic in Soft tissue chapter)
Essential features
  • Vascular malignancy most often seen in AIDS patients with HHV8 infection
  • Rare in gastrointestinal tract
  • Most common gastrointestinal malignancy attributable to AIDS (Am J Gastroenterol 1991;86:715)
  • Currently rare; incidence decreased from use of HAART for AIDS treatment
  • HHV8 infection
Clinical features
Prognostic factors
Case reports
  • Chemotherapy and radiation preferred over surgery
Clinical images

Images hosted on other servers:

Kaposi sarcoma

Gross description
  • Reddish brown to purple macules or polyps, typically 0.5 - 1.5 cm
Microscopic (histologic) description
  • Lamina propria based lesion composed of spindle cells with mild to moderate atypia, arranged in vague fascicles and separated by slit-like vessels
  • Extravasated red blood cells common
  • PAS positive, diastase resistant hyaline globules sometimes seen
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.

H&E, intermediate power

H&E, high power

Images hosted on other servers:

Low power

High power


Positive stains
Negative stains
Sample pathology report
  • Rectum, mass, biopsy:
    • Vascular proliferation most consistent with Kaposi sarcoma (see comment)
    • Comment: An immunostain for HHV8 is positive in the lesional cells.
Differential diagnosis
Board review style question #1

Which of the following is considered a risk factor for developing Kaposi sarcoma?

  1. Female sex
  2. HIV / AIDS
  3. Prior bariatric surgery
  4. Young age
Board review style answer #1

Comment Here

Reference: Kaposi sarcoma
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