We report the unique association of Masson's pseudoangiosarcoma (endothelial papillary hyperplasia) and extramedullary hematopoiesis. The lesion was present as a violaceous nodule on the side of the tongue of a 78-year-old man with history of multiple myeloma and long-standing mild anemia. This association between a peculiar form of thrombus organization and extramedullary hematopoiesis has been reported previously only once, in an infant with a cranial hematoma, and raises interesting pathogenetic questions.