Thrombocytosis associated with solid tumors in children.

The association between thrombocytosis and malignant disease was first described by Levin and Conley in 19641 but its pathogenesis remains unknown. We have studied the platelet counts in 108 children with solid tumors presenting to this hospital over the last 5 years. Thrombocytosis was defined as a platelet count over 400 × 109/L and was noted in 43 children (40%) at presentation; in the great majority of cases the thrombocytosis could not be ascribed to infection or hemorrhage. The platelet counts in relation to the six commonest diagnoses are shown in Figure 1. The association was particularly marked in the case of hepatic tumors, where 8 out of 10 patients had platelet counts at presentation above 400 × 109/L with a mean of 647 ± 306 (SD) × 109/L (range 294-1310). Thrombocytopenia (platelet count less than 150 × 109/L) was noted in 5 children at presentation; 2 of these had morphological evidence of bone marrow infiltration.