Downgraded non-Hodgkin's lymphoma in the neck occurring as a secondary malignancy.

While the histologic progression from low-grade non-Hodgkin's lymphoma (NHL) to intermediate- or high-grade NHL has been well documented, a rare phenomenon called downgrading in which the histologic conversion of a low-grade NHL occurs after treatment for intermediate- or high-grade NHL has recently been recognized. We report the clinical, immunologic, and genetic features of a patient with a diffuse NHL (intermediate grade) who initially achieved complete remission by both chemotherapy and radiation therapy and then presented with a follicular NHL (low grade) 14 years later. The immunohistochemical study of the lymphoma cells showed B lymphocytes in biopsied lymph nodes at both the initial and the second diagnosis. However, a polymerase chain reaction (PCR) analysis for the immunoglobulin gene rearrangement indicated that the clone of the initial intermediate-grade NHL showed monoclonal cell population, and was distinct from that of the second downgraded form. Given the PCR results and the clinical features, we suggest that a follicular NHL can occur as a secondary malignancy following combined therapy for a diffuse NHL.