"Lennert's lymphoma" with transformation to malignant lymphoma, histiocytic type (immunoblastic sarcoma).

Two cases of a recently described lymphoproliferative disorder called "Lennert's lymphoma" are presented. In both cases, the proliferation evolved into a frank malignant lymphoma of large lymphoid cells. This phenomenon has not been previously reported to occur in this disease. Immunohistologic study of the biopsy material in both cases suggest that it may be a T-cell proliferation. The possibility that "Lennert's lymphoma" is not a neoplasm but an abnormal immune reaction with similarities to angioimmunoblastic lymphadenopathy is raised. Whatever its nature, the potential for "Lennert's lymphoma" to transform into a frankly malignant tumor is documented.