All are true about histological feature of Kaposi's sarcoma except

Ref Robbins 9/e p254,8/e p529; 7/e p549 Neoplasms. Patients with AIDS have a high incidence of ceain tumors, paicularly Kaposi sarcoma, non-Hodgkin lymphomas, and cervical cancer in women. The common feature of all of these diverse neoplasms is that the tumor cells in each are typically infected by an oncogenic virus. The basis of the increased risk of virus-associated malignancy is multifactorial, but defective T cell immunity is believed to be the predominant contributor. Kaposi sarcoma, a vascular tumor that is otherwise rare in the United States (Chapter 9), was once the most common neoplasm in AIDS patients but its incidence has decreased significantly with anti-retroviral therapy. The tumor is far more common among homosexual or bisexual males than in intravenous drug abusers or patients belonging to other risk groups. The lesions can arise early, before the immune system is compromised, or in advanced stages of HIV infection. Unlike the lesions in sporadic cases of Kaposi sarcoma, those that occur in patients with AIDS are multi- centric and tend to be more aggressive; they can affect the skin, mucous membranes, gastrointestinal tract, lymph nodes, and lungs. The lesions contain spindle cells that share features with endothelial cells and smooth muscle cells and are believed to be lymphatic endothelial cells or mesenchymal cells that can form vascular channels. In dif- ferent patients, the lesions are monoclonal or oligoclonal or even polyclonal, an unusual feature shared by other pro- liferations driven by oncogenic viruses, such as ceain EBV-related B cell proliferations. Kaposi sarcoma is caused by a herpesvirus called Kaposi sarcoma herpesvirus (KSHV), or human herpesvirus-8 (HHV-8). The mechanisms by which the virus causes the vascular proliferation are unceain. One hypothesis is that KSHV infects lymphatic endothelial or other cells, and in conce with cytokines produced by HIV-infected immune cells, stimulates proliferation of the endothelial cells. The KSHV genome contains homologues of several human oncogenes and cytokines that may contribute to the growth and survival of the proliferating vessels. B cell non-Hodgkin lymphomas constitute the second most common type of AIDS-associated tumors. These tumors are highly aggressive, occur most frequently in severely immunosuppressed patients, and involve many extranodal sites. The brain is the most common extranodal site in late- stage HIV infection, and hence primary lymphoma of the brain is considered an AIDS-defining condition. Close to 100% of these brain lymphomas are EBV-related. In com- parison only 30% to 40% of lymphomas occuring earlier in the course of HIV infection are EBV-related, emphasizing the contribution of other factors, such as chronic B cell hyperstimulation, to lymphoma risk in HIV-infected indi- viduals. Another, less common AIDS-related lymphoma is primary effusion lymphoma, which grows exclusively in body cavities, manifesting as pleural, peritoneal, or peri- cardial effusions. This rare tumor is always associated with KSHV, and in many cases the tumor cells are co-infected with both KSHV and EBV. The incidence of cervical carcinoma also is increased in patients with AIDS. This correlation is attributable to the high prevalence of human papillomavirus infection among patients with AIDS, whose immune systems are compro- mised. This virus is believed to be intimately associated with squamous cell carcinoma of the cervix and its precur- sor lesions, cervical dysplasia and carcinoma in situ (Chapter 18). Hence, gynecologic examination should be pa of the routine evaluation in HIV-infected women. In general, the incidence of the classical "AIDS-defining cancers"--Kaposi sarcoma, EBV-associated tumors, and cervical cancer--has decreased significantly with the use of antiretroviral therapy, but the relative incidence of other tumors considered "non-AIDS-defining cancers" is ctually increasing. This latter group includes liver cancer, anal cancer, and Hodgkin lymphoma, all of which are types of tumors associated with various viral infections.