Extramedullary haemopoietic tumours complicating polycythaemia vera.

A 52 year old man with newly diagnosed polycythaemia vera in proliferative phase developed widespread extramedullary haemopoiesis (EMH), and died as a result of cervical cord compression. At necropsy, microscopic areas of primitive cells characteristic of granulocytic sarcoma were found within a large tumour of EMH in the right retroperitoneal region. Ultrastructural analysis showed unusual hexagonal inclusions within the cytoplasm of these primitive cells. Clinicians should be aware of the possibility of discrete haemopoietic tumours, whether EMH or granulocytic sarcoma, in patients with polycythaemia vera as well as in other myeloproliferative disorders.