Non-Hodgkin's lymphoma following untreated essential thrombocythemia.

The coexistence of essential thrombocythemia (ET) and non-Hodgkin's lymphoma (NHL) is an extremely rare event, with only two such cases having been reported in the medical literature. We describe here a 25-year old woman who developed high-grade B-cell NHL of the stomach three years after the diagnosis of ET, for which she had received no treatment, due to her young age and the lack of thrombotic risk factors other than thrombocytosis. The lymphoma showed a favorable response to CHOP chemotherapy, whereas the thrombocytosis remained unchanged throughout the patient's clinical course. The possible etiologic and pathogenetic mechanisms leading to the association of these two disorders are discussed. Given the relative frequency of ET and the fact that the present case represents only the third reported instance of NHL developing in such patients, the coincidental ocurrence of both diseases is a possibility that cannot be excluded.