Hemolytic uremic syndrome is a rare entity in patients with carcinoma and 
presents with a triad of renal insufficiency, microangiopathic hemolytic anemia, 
and thrombocytopenia. We report this syndrome for the first time in a patient 
with small cell lung carcinoma. Spontaneous platelet aggregation of washed 
normal platelets was demonstrated using patient plasma. Circulating immune 
complex levels were not elevated. The entity completely resolved after treatment 
with plasma, vincristine, aspirin, and dipyridamole.