Extramedullary hematopoeisis within a convexity meningioma

Abstract

Background Hematopoiesis outside the bone marrow is known to occur in patients with severe anemia, leukemia, polycythemia, or myelofibrosis, and in patients affected by chronic poisoning by marrow-toxic substances. Case Description A 66-year-old right-handed man complained of 4 days of terrible right-sided, sharp, and shooting headache for which he saw his primary care provider. Routine laboratory examination showed a WBC count of 30 800/ μL. Neuroimaging showed a large, right frontotemporal, extra-axial, heterogeneously enhancing, dural based mass with associated recent intramural hemorrhage with evidence of midline shift and uncal herniation. The mass was resected using a right-sided extended craniotomy with anterior fossa and middle fossa approach. A hematoxylin-eosin–stained biopsy specimen showed whorls of tumor cells, diagnostic of a meningioma. Interspersed within the tumor bulk were nucleated RBCs, representing areas of extramedullary erythropoiesis within a meningioma. Flow cytometric evaluation confirmed the clinical suspicion of an underlying chronic lymphocytic leukemia. Conclusion Occurrence of extramedullary hematopoiesis within a meningioma is extremely rare. Various theories may explain the occurrence of extramedullary hematopoiesis occurring within a meningioma in our patient, such as hematopoietic differentiation of multipotent mesenchymal tumor cells; direct extension of hematopoietic activity from the neighboring marrow cavity; displacement from bone marrow of stem cells that settle and develop in tissues where capillaries and blood vessels proliferate, such as a meningioma; or congenital heterotopia of totipotent connective tissue cells, which, under certain circumstances, may transform into hematopoietic tissue.