Postsplenectomy sclerosing extramedullary hematopoietic tumor with unexpected good clinical evolution: morphologic, immunohistochemical, and molecular analysis of one case and review of the literature.

Sclerosing extramedullary hematopoietic tumor has been described as a rare manifestation of chronic myeloproliferative neoplasm. The lack of knowledge about this entity has caused it to be mistaken for many types of nonhematopoietic and hematopoietic tumors. We present the case of a 71-year-old lady with a long history of primary myelofibrosis, which developed multiple abdominal sclerosing extramedullary hematopoietic tumors with good clinical evolution. Nonchronic myeloid leukemia myeloproliferative neoplasm included a JAK2 mutation as part of the diagnosis algorithm. Particularly, idiopathic myelofibrosis is related with a JAK2 mutation in 50% of the cases with a pejorative prognosis. The absence of JAK2 demonstrated in the paraffin samples of the tumors may be related to the unusual evolution in this particular case. Morphologically differential diagnoses considered in the evaluation of this entity and in our case included sarcomas mainly liposarcoma, anaplastic carcinoma, and Hodgkin lymphoma.