Merkel cell carcinoma and human immunodeficiency virus: More than a non-acquired immunodeficiency syndrome-defining tumor?

The incidence of non-acquired immunodeficiency syndromedefining cancers is increasing in human immunodeficiency virus (HIV)-infected persons at a rate that is disproportionate to similar malignancies in the general population. The effect of HIV infection on latent oncogenic viruses and immune surveillance (the latter measuredby the absolute CD4 ⁺ T-cell lymphocyte count) and the role of highly active antiretroviral therapy are considered contributing factors in the development of this epidemiologic trend. Merkel cell carcinoma (MCC), a rare but aggressive cutaneous malignancy, occurs at a disproportionately higher frequency in HIV-infected individuals, even in the context of relatively spared CD4 ⁺ T-cell lymphocyte counts. A newly identified polyomavirus has been recently isolated from the tumoral genome of MCC, suggesting a viral oncogenic pathogenesis. We report a case of metastatic MCC in an HIV-infected patient that only became clinically evident after he achieved undetectable HIV RNAviral levels for the first time. We review the association of MCC with HIV and discuss the relationship of moderate but prolonged immunosuppression, which results from HIV disease, and its connection with non-acquired immunodeficiency syndrome-defining cancers while suggesting that MCC and other malignancies may need to be reconsidered for classification as acquired immunodeficiency syndrome-defining conditions.