Intracranial extramedullary hematopoiesis associated with pilocytic astrocytoma: a case report.

Intracranial EMH is only occasionally found in primary brain tumors (mostly hemangioblastomas) and, to our knowledge, this is the first case of EMH associated with an astrocytoma. Intracranial extramedullary hematopoiesis (EMH) is described in a 29-year-old man with a recurrent pilocytic astrocytoma in the tectal region. Special stains confirmed the identities of erythroid, myeloid and megakaryocytic cells. The patient had no evidence of a predisposing bone marrow disorder or systemic EMH. Although the presence of multinucleated and blastic cells associated with a low-grade brain neoplasm is unusual, recognition of hematopoietic lineages allows EMH to be readily identified. Another tumor resection after a year of follow-up confirmed the absence of malignant progression in this recurrent astrocytoma. The small number of cases describing intracranial EMH in the absence of systemic hematologic abnormalities are correlated with the findings in this case. The low incidence of intracranial EMH indicates that cells with hematopoietic potential are seldom exposed to a supportive microenvironment within the central nervous system. However, intracranial EMH should be included as a potential, ancillary diagnosis when considering brain lesions. This may be particularly true if medical therapies involving growth factors or stem cells are found to promote hematopoiesis.