RESUMEN
Splenomegaly is a key clinical manifestation of myelofibrosis, and splenectomy is currently indicated in patients with drug refractory, symptomatic splenomegaly or with the aim of improving refractory cytopenias. Transformation to acute myeloid leukemia occurs in up to 20% of patients with myelofibrosis, while cases of myeloid sarcoma have been reported very unfrequently. In this manuscript, we report the case of a 60-year-old man with a history of primary myelofibrosis who underwent splenectomy because of drug-refractory massive splenomegaly, systemic symptoms and anemia. At the opening of the peritoneal cavity, the spleen resulted massively enlarged and tenaciously entrapped by a pervasive neoplastic-like tissue. The extensive involvement of the abdomen fatally complicated the surgical procedure. At postmortem examination, the spleen showed a diffuse infiltration of immature cells that were also found in the peritoneum, bowel, liver, lungs and myocardium. After immunohistochemical, cytogenetic, flow cytometric and molecular characterization of neoplastic population, a diagnosis of disseminated myeloid sarcoma of the spleen was made. This case report highlights a very unusual case of myeloid sarcoma originating from the spleen in a patient with myelofibrosis who had no evidence of bone marrow or peripheral blood involvement by leukemic cells. Molecular characterization showed that leukemic cells originated from the founding clone of the chronic phase. The sarcoma could not be suspected based on clinical findings and was diagnosed only at the time of surgical procedure and autopsy. This case suggests that leukemic transformation of myelofibrosis can originate outside the bone marrow and, presumably rarely, present as a granulocytic sarcoma.