Extramedullary solid tumors of early granulocytic and monocytic precursors are a rare manifestation of acute non lymphoblastic leukemias. They may develop during the course, or be the presenting sign, of leukemia. We describe a case of myelomonocytic tumors involving the skin and the stomach as primary manifestations of leukemia. Two months later the patient developed acute myelomonocytic leukemia with a rapidly fatal course. At autopsy, multiple tumors were found in the skin, the peridural space, the muscles, the peritoneum, the pleura and in several organs, such as in the lungs, the kidneys, the gallbladder and in the whole gastrointestinal tract. The many synonyms of these tumors, the localisation, the chronology of the clinical manifestations and the various problems in the diagnosis are discussed. In the differential diagnosis of histiocytic lymphoma, identification of myelomonocytic differentiation in neoplastic cells should be done, using special techniques, such as immunoperoxidase and cytochemical stains for esterases.