Sclerosing Extramedullary Hematopoietic Tumor Mimicking Intra-abdominal Sarcoma

Sclerosing extramedullary hematopoietic tumor (SEMHT) is a rare tumor that occurs in patients with chronic myeloproliferative disorders (CMPDs). The tumor is classified in the chronic idiopathic myelofibrosis (MF) subgroup, and cases have been reported at various localizations since 1980 [1-4]. Such tumors are usually seen in the abdominal organs, retroperitoneum, and mesenteric region [3]. The clinical, radiological, and morphological features may complicate differentiation from sarcoma, carcinoma, and lymphoma. It is sometimes also difficult to differentiate between a SEMHT and extramedullary hematopoiesis (EMH). These two lesions have similar clinical features, but EMH is morphologically more cellular. To aid in the differentiation, SEMHT has a more solid mass appearance with dense fibrosis and atypical megakaryocytes [3]. EMH is the presence of hematopoietic tissue in locations other than the bone marrow. The basic mechanism is bone marrow dysfunction and decreased production of hematopoietic cells, followed by production of bone marrow cells in other organs and tissues. EMH is seen in many disorders such as sickle cell anemia, hemoglobinopathies, thalassemia, hereditary spherocytosis, and MF [5]. EMH is most commonly observed in the liver and spleen and is rarely found in the peritoneum, lymph nodes, kidneys, thymus, central nervous system, retroperitoneum, myocardium, uterus, pleura, paraspinal region, or intestines [6-9].