Phytohemagglutinin skin tests in cancer patients.

Phytohemagglutinin (PHA) stimulates blastic transformation of normal lymphocytes in vitro and when injected intradermally produces a skin response histologically similar to a delayed hypersensitivity reaction. We investigated the skin test responses to PHA, mumps, candida, and varidase (SK-SD) and the PHA-induced lymphocyte transformation in patients with malignant neoplasms. Increased incidence of anergy to recall antigens and unresponsiveness to PHA skin testing was observed in patients with lymphoreticular malignancies but not in those with solid tumors. There was a direct correlation between skin test reactivity to at least one recall antigen and/or PHA and survival in lymphoma patients. This was true of both short and long terms survival in Hodgkin's disease and of survival at least through 42 months in non-Hodgkin's lymphomas. In vitro stimulation of lymphocytes with PHA did not correlate with PHA skin test reactivity. We conclude that PHA skin testing is a useful adjunct in the evaluation of patients with lymphoreticular malignancies.