The vascular tumours of note are epitheliod haemangioendothelioma, angiosarcoma of the soft tissues and Kaposi sarcoma.
Kaposi sarcoma arises in four different patient populations:
- Classical: Older people of Mediterranean descent (lower limbs)
- Endemic: Children and adults living in Equatorial Africa (extremities)
- Iatrogenic: Arising in immunosuppressed patients (eg. post-transplant, dialysis) (lower limbs)
- HIV-associated: Arising in patients infected with HIV (face and oral cavity, genitals, lower limbs)
It is a rare disease outside of the HIV-associated group, and is becoming less common in that group.
Epithelioid haemangioendothelioma is a rare neoplasm with intermediate aggressiveness between benign haemangioma and angiosarcoma.
Angiosarcoma is also rare and is slightly more common in older people; this is in contrast to cutaneous angiosarcoma which is far more common in the elderly.
Aetiology and Pathogenesis
Specific causes of angiosarcoma or EHE have not been determined.
For Kaposi sarcoma, infection with human herpesvirus 8 is a required step in the pathogenesis. Additional impact from genetic, environmental and immune system function are required for development of Kaposi sarcoma.
Kaposi sarcoma initlally appears as a patch of red or purple discolouration. They progress to nodules. They are frequently multiple and recurrent. In some cases they metastasise to regional nodes. Distant metastases are rare except late in the disease course. Aside from the AIDS associated disease, which occurs in the face and genitals as well, most lesions occur on the legs.
This lesion often arises in the wall of a named vein or artery. It can cause compression of the vessel and lead to ischaemic or thrombotic symptoms. Local excision is usually curative but recurrences are common. Metastases are uncommon but fatal.
Deep tissue angiosarcoma presents similarly to other soft tissue sarcomas. Those of the skin have a red to purple nodular rash. Metastases to lymph nodes can occur as well as distant metastases.
The lesion appears as a red or purple patch, plaque or nodule which may be single, multiple, or coalesced. Microscopically, the lesion consists of dilated vascular channels with surrounding spindle cells. More advanced lesions consist mostly of anaplastic spindle cells which compress the vascular channels.
The tumour consists of large endothelial cells that resemble an epithelioid neoplasm in some respects. Large vascular channels are not seen. Cells may contain small channels within their cytoplasm (similar to a capillary) that contain erythrocytes.
A variety of appearances is possible. Some variants form large vascular channels lined by endothelial cells with a spindle cell component; others form solid sheets of epithelioid cells. Immunohistochemistry positivity for CD31 is almost diagnostic. Genetic changes are complex.