Evolution of a lymphoma with helper T cell characteristics in Sezary syndrome

Abstract

A patient with Sezary syndrome presented with disease limited to the skin and circulating abnormal lymphocytes but subsequently developed a diffuse undifferentiated lymphoma. Malignant cells from a lymph node effaced with the morphologically undifferentiated lymphoma were characterized as being of thymus-derived (T cell) origin. We have previously shown that circulating malignant lymphocytes from some patients with Sezary syndrome are malignant cells that function as helper cells for Ig biosynthesis by normal B lymphocytes. In the present case, either peripheral blood lymphocytes, comprised mainly of Sezary cells, or cells from the malignant lymph node, containing morphologically undifferentiated lymphomatous cells, greatly augmented pokeweed mitogen-driven IgM synthesis by purified normal B lymphocytes. Thus both the peripheral blood lymphocytes and lymphoma cells from this patient could perform a helper function for Ig biosynthesis in vitro. The undifferentiated lymphoma in this case probably represented an extension of the original malignant clone of helper T cells rather than an unrelated lymphoma that developed de novo. This case illustrates that a T cell malignancy may be morphologically either relatively well differentiated, as in the circulating Sezary cells, or relatively undifferentiated, as in the lymphomatous node, and still express a residual helper T cell function. Furthermore, this case supports the view that it may be possible to classify certain morphologically undifferentiated lymphomas (or immunoblastic sarcomas) according to their immunoregulatory capacity in vitro.