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Skin - Nonmelanocytic tumors

Vascular tumors

Kaposi sarcoma

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 19 August 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● Low grade vascular neoplasm, first described by Kaposi in 1872
● Derived from vasoformative mesenchymal multipotential cells
● Either classic or HIV related

Classic Kaposiís sarcoma


● Non-HIV associated
● 10% of all malignant tumors in equatorial (central) Africa, usually young adults and children
● Also common in some Mediterranean regions among males
● Rare in US
● Usually prolonged course
● Elderly patients may die of recurrent disease
● Poor prognosis if over 50 years old and immunosuppression or in African cases

HIV associated Kaposiís sarcoma


● More common than classic form in US and Western world due to HIV (usually male homosexuals)
● Similar to cases associated with organ transplant recipients, systemic Castlemanís disease, angioimmunoblastic lymphadenopathy, lymphoma, other malignancies
● More rapid clinical course than classic disease
● Frequent involvement of lymph nodes, lungs, GI tract


● Radiotherapy, chemotherapy, excision

Gross description

● Multiple blue/violet dermal nodules/plaques on feet and legs, progressing proximally
● May be polypoid and resemble pyogenic granuloma
● Nodules may also be in subcutis, but these are clinically indolent

Macular stage:
● Red-blue cutaneous discoloration, often lower extremity

Micro description

● Spindle cells forming slits with extravasated red blood cells, hemosiderin laden macrophages, lymphocytes and fibrosis (Diagn Pathol 2008;3:31)
● Minimal atypia
● May have numerous eosinophilic, PAS+ hyaline bodies (may be ingested erythrocytes)
● Moderate mitotic activity
● Early changes may be limited to spindle cells in papillary dermis and vasculature around sweat glands, and not be diagnostic
● Note: AIDS patients also have vascular lesions resembling angiosarcoma, epithelioid hemangioma, lymphangioma

Macular stage:
● Thin-walled, angulated vessels throughout dermis, with hemosiderin and plasma cell infiltrate

Patch stage:
● Angulated lumina that dissect dermal collagen
● Vessels may proliferate around well-developed round venules (premonitory sign)
● Angiomatoid vascular spaces with red blood cells are surrounded by spindle cells in short fascicles

Tumor stage:
● Solid nodules with extensive spindle cells and red blood cells in slit-like lumina
● No/rare mitotic activity or atypia

Lymphangioma-like variant:
● Thin, angulated vessels with no red blood cells

Micro images

Patch stage

Plaque stage

Nodular (tumor) stage


Positive stains

● CD31, CD34, Factor VIII related antigen, podoplanin (D2-40)
● Also thrombomodulin, latent nuclear antigen-1 of HHV-8 (Kaposi sarcoma-associated herpes virus, Mod Pathol 2004;17:456)
● Note: HHV8 also present in primary effusion lymphoma, some cases of multicentric Castlemanís disease, reactive angioendotheliomatosis, plasmacytic lymphoma

Negative stains

● Keratin, desmin

Molecular description

● Diploid and clonal
● HHV8 present in almost 100% of lesions (classic, HIV, or other types)

Differential diagnosis

● Acroangiodermatitis
● Angioma
● Angiosarcoma
● Arteriovenous malformation
● Bacillary angiomatosis
● Benign fibrous histiocytoma
● Cutaneous angiosarcoma
● Fibrosarcoma
● Other vascular tumors
● Pigmented purpuric dermatosis
● Pyogenic granuloma
● Sarcomatoid carcinoma
● Spindle cell hemangioendothelioma (usually dermis and subcutis)
● Tufted angioma

End of Skin - Nonmelanocytic tumors > Vascular tumors > Kaposi sarcoma

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