Soft tissue
Vascular
Intermediate (locally aggressive / rarely metastasizing)
Kaposi sarcoma
Authors: Michella Whisman, M.D., Jerad M. Gardner, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Last author update: 22 January 2019
Last staff update: 6 October 2022 (update in progress)
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Kaposi sarcoma [title] soft tissue
Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Laboratory | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Differential diagnosis | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Whisman M, Gardner JM. Kaposi sarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuekaposi.html. Accessed June 8th, 2023.
Definition / general
- Vascular neoplasm caused by human herpesvirus 8 (HHV8)
- Tends to be indolent but may be locally aggressive
Essential features
- Etiologic agent of all forms and cases is human herpesvirus 8 (HHV8), HHV8 immunostain will distinguish it from other vascular tumors on the differential
- Microscopic morphology is similar for all clinical variants
- Slit-like vascular spaces formed by spindled endothelial cells with minimal to moderate atypia; hemorrhage, hemosiderin and plasma cells are key histologic clues
- Can histologically mimic angiosarcoma; distinction is critical, as behavior and treatment are very different
ICD coding
- ICD-10: C46 - Kaposi sarcoma
Epidemiology
- Depends on the clinical variant of Kaposi sarcoma (4 subtypes) (Dermatol Ther (Heidelb) 2016;6:465):
- Classic / sporadic
- Elderly men > women
- Lower extremity skin lesions
- Central equatorial Africa, Mediterranean and Eastern European
- May be associated with secondary malignancy
- Clinically indolent course
- Endemic / African
- Lower extremity skin lesions
- Children and young to middle aged adults
- Not related to HIV
- Sub-Saharan Africa
- May be aggressive if lymph nodes involved
- Iatrogenic
- Predominantly transplant associated
- Skin, visceral and mucosa involvement
- AIDS associated
- Patients infected with HIV1
- Predilection for certain risk groups
- Risk for homosexual men greater than hemophiliac
- Affinity for skin but may be disseminated
- Most aggressive of all Kaposi subtypes
- Classic / sporadic
Sites
- Skin is predominant site
- May also affect lymph nodes, visceral organs or mucosa
Pathophysiology
- Endothelial cells infected with HHV8 undergo altered lymphatic differentiation and manufacture cytokines creating a favorable milieu for angiogenesis (Philos Trans R Soc Lond B Biol Sci 2017;372)
Etiology
- HHV8
Clinical features
- Progressive, enlarging red to violaceous skin lesions (Arch Pathol Lab Med 2013;137:289)
- Patch stage
- Red or purple macules or patches
- Plaque stage
- Thickened red, purple or brown plaques
- Tumor stage
- Nodule formation
- Patch stage
- All four clinical subtypes of Kaposi may show these stages
- Multiple different stages may be present simultaneously
Laboratory
- HHV8 positive peripheral blood, as well as lesional tissue
Radiology description
- Imaging particularly useful to evaluate disseminated disease and depth of involvement
- Features dependent upon site of involvement (Radiographics 2018;38:2051, Radiographics 2006;26:1169)
Radiology images
Images hosted on other servers:
Pulmonary Kaposi sarcoma
Prognostic factors
- Clinical variant
- Stage of disease
- Status of immune system
Case reports
- 25 year old and 30 year old HIV- men with disseminated Kaposi sarcoma (Am J Case Rep 2018;19:868)
- 48 year old HIV- man with ulcerative colitis (World J Clin Cases 2017;5:423)
- 52 year old, HIV+ man with epithelioid morphology (J Cutan Pathol 2018;45:526)
- 71 year old, HIV- man with nodular scrotal lesions (Int J Surg Case Rep 2014;5:1086)
- 71 year old, HIV- man with dark toe lesions (J Dermatol Case Rep 2013;7:97)
Treatment
- No definitive cure but variety of possible treatments for palliation (Am J Clin Dermatol 2017;18:529)
- Removal of immunosuppressive agents in iatrogenic variant
- Highly active antiretroviral therapy (HAART) for AIDS associated variant
- Other options include: surgical excision (of symptomatic lesions only; wide local excision usually not indicated), radiation, systemic chemotherapy, topical drugs, cryoablation therapy
Clinical images
Contributed by Mark R. Wick, M.D.
Advanced disease
Images hosted on other servers:
Reddish purple nodules
Lesions
Intraoral lesion
Violaceous plaques
Gross description
- Red to purple lesions
- Hemorrhagic on cut surface, especially visceral lesions
Gross images
Images hosted on other servers:
Infiltration of lung parenchyma
Reddish nodules on gastric mucosa
Irregular masses in the liver
Microscopic (histologic) description
- Patch stage:
- Dilated vascular channels dissecting through dermal collagen
- Promontory sign: tumor vascular channels surround and entrap native vessels (classic but uncommon feature)
- May be very subtle in early lesions
- Dilated vascular channels dissecting through dermal collagen
- Plaque stage:
- More extensive, compressed, slit-like vascular channels infiltrating deeper dermis
- Infiltrative proliferation of spindled endothelial cells (may resemble fibroblasts)
- Spindle cells infiltrating and destroying eccrine coils is very characteristic
- Tumor (nodular) stage:
- Discrete nodules composed of intersecting fascicles of uniform spindle cells
- Intervening blood filled spaces between spindle cells
- Slit-like spaces (longitudinal section)
- Sieve-like spaces (cross section)
- Intracytoplasmic hyaline globules may be seen
- All stages:
- Mitoses common but pleomorphism usually minimal
- Rare poorly differentiated cases have severe pleomorphism (must confirm with HHV8 immunostain to exclude angiosarcoma)
- Extravasated erythrocytes and hemosiderin common findings
- Plasma cells present in most cases
- Mitoses common but pleomorphism usually minimal
Note:
- Distinction of stage is not required in pathology report (Diagn Pathol 2008;3:31, Arch Pathol Lab Med 2013;137:289)
Microscopic (histologic) images
Contributed by Michella Whisman, M.D.
Early lesion subtle at low power
Dilated channels visible at higher power
Inflammatory appearance
Lymphoplasmacytic infiltrate
Hemosiderin deposition
Spindle cell proliferation
Tumor (nodular) stage
Sieve-like pattern
Blood filled channels
Spindle cells without blood
Ill defined fasicles
HHV8
ERG
HHV8 can be missed at low power
HHV8 with focal positivity
Contributed by Mark R. Wick, M.D.
Hyaline globules
Cytology description
- Cohesive spindle cells in hemorrhagic background (Arch Pathol Lab Med 2013;137:289)
Cytology images
Contributed by Michella Whisman, M.D.
Lymph node touch prep
Positive stains
- HHV8 (also referred to as LANA1) nuclear staining in virtually 100% of cases
- May be focal, especially in early patch stage lesions
- Typically has unique granular / speckled / stippled nuclear staining pattern
- ERG, CD34, CD31, D2-40 (Am J Surg Pathol 2011;35:432)
- Subset of cases lack CD31 expression (Arch Pathol Lab Med 2012;136:1329)
- Hyaline globules are PAS positive, diastase resistant
Negative stains
Differential diagnosis
- Angiosarcoma
- Infiltrative vascular channels, usually with marked nuclear atypia
- HHV8 negative
- Usually arises in head / neck of sun damaged elderly or at site of irradiation
- Severe vascular stasis (acroangiodermatitis)
- Fibroblastic spindle cell component rather than endothelial
- Negative for vascular markers
- HHV8 negative
- Hobnail hemangioma (targetoid hemosiderotic hemangioma)
- Slit-like vascular channels but no spindle cell proliferation
- HHV8 negative
- Spindle cell hemangioma
- Spindled endothelial cells with slit-like channels but also has epithelioid cells
- Biphasic: solid spindled / epithelioid zone and zone of dilated cavernous vessels
- Usually lacks plasma cells and hemorrhage
- HHV8 negative
- Kaposiform hemangioendothelioma
- Unique whorled and nodular pattern of spindled endothelial cells
- Hemorrhage and plasma cells uncommon
- Usually in young children or infants
- HHV8 negative
Board review style question #1
The pictured tumor is from the foot of a 75 year old man of Mediterranean descent. The virus
associated with the diagnosis also causes which of the following?
- Adult T cell leukemia
- Burkitt lymphoma
- Primary effusion lymphoma
- Squamous cell carcinoma of the cervix
Board review style answer #1
C. The pictured tumor is Kaposi sarcoma which is caused by HHV8. HHV8 may also lead to primary effusion lymphoma and multicentric Castleman disease. Squamous cell carcinoma of the cervix is caused by HPV. Burkitt lymphoma can be associated with EBV. Adult T cell leukemia is associated with HTLV1.
Comment here
Reference: Kaposi sarcoma
Comment here
Reference: Kaposi sarcoma
Board review style question #2
Which histologic finding would favor a diagnosis of Kaposi sarcoma over angiosarcoma?
- Infiltrative, anastomosing vascular channels
- History of radiation exposure
- Marked cytologic atypia
- Positive LANA1 stain
Board review style answer #2
