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Figure 15.25 Angiosarcoma spleen. A, Gross appearance of lobulated masses of grey white necrotic and haemorrhagic parenchyma. B, The
tumour cells show proliferation of moderately pleomorphic anaplastic cells. C, These tumour cells show positive staining for endothelial marker,
CD34.

especially on the legs. Involvement of visceral organs occurs PATHOGENESIS. Pathogenesis of Kaposi’s sarcoma is
in about 10% cases after many years. complex. It is an opportunistic neoplasm in immunosup-
pressed patients which has excessive proliferation of spindle
2. African (Endemic) Kaposi’s sarcoma. This form is
common in equatorial Africa. It is so common in Uganda cells of vascular origin having features of both endothelium
that it comprises 9% of all malignant tumours in men. It is and smooth muscle cells:
found in younger age, especially in boys and in young men Epidemiological studies have suggested a viral association
and has a more aggressive course than the classic form. The implicating HIV and human herpesvirus 8 (HSV 8, also called
disease begins in the skin but grows rapidly to involve other Kaposi’s sarcoma-associated herpesvirus or KSHV).
tissues, especially lymph nodes and the gut. Occurrence of Kaposi’s sarcoma involves interplay of
HIV-1 infection, HHV-8 infection, activation of the immune CHAPTER 15
3. Epidemic (AIDS-associated) Kaposi’s sarcoma. This system and secretion of cytokines (IL-6, TNF-α, GM-CSF,
form is seen in about 30% cases of AIDS, especially in young basic fibroblast factor, and oncostain M). Higher incidence
male homosexuals than the other high-risk groups. The of Kaposi’s sarcoma in male homosexuals is explained by
cutaneous lesions are not localised to lower legs but are more increased secretion of cytokines by their activated immune
extensively distributed involving mucous membranes, system.
lymph nodes and internal organs early in the course of
disease. Defective immunoregulation plays a role in its
pathogenesis is further substantiated by observation of second
4. Kaposi’s sarcoma in renal transplant cases. This form is malignancy (e.g. leukaemia, lymphoma and myeloma) in
associated with recipients of renal transplants who have been about one-third of patients with Kaposi’s sarcoma.
administered immunosuppressive therapy for a long time.
The lesions may be localised to the skin or may have MORPHOLOGIC FEATURES. Pathologically, all forms
widespread systemic involvement. of Kaposi’s sarcoma are similar The Blood Vessels and Lymphatics

Figure 15.26 Kaposi’s sarcoma in late nodular stage. There are slit-like blood-filled vascular spaces. Between them are present bands of
plump spindle-shaped tumour cells.