Extramedullary hematopoiesis—the presence of hematopoietic activity in sites outside of the bone marrow—can occur in malignant and non-malignant hematologic diseases, and they may be a complication of primary myelofibrosis.
Extramedullary hematopoiesis (EMH)—the presence of hematopoietic activity in sites outside of the bone marrow, such as the liver or spleen—can occur in malignant and non-malignant hematologic diseases, and they may be a complication of primary myelofibrosis (PMF). EMH has been observed in the lymph nodes of some patients with PMF, and a recent case report describes a presentation of lymphadenopathy, secondary to EMH, that occurred as a patient’s first manifestation of PMF.
The report describes a 63-year-old patient who experienced generalized lymphadenopathy for 9 months, and had fever, night sweating, and weight loss. She had no history of hematologic illness. Computed tomography revealed lymphadenopathy in the mediastinal, abdominal, and pelvic lymph nodes, as well as enlargement of the liver and spleen. Additionally, sclerotic lesions throughout the patient’s skeletal system were observed.
A lymph node biopsy showed no evidence of malignancy, though large abnormal cells were observed in the lymph nodes. A liver biopsy was negative for malignancy, but it showed inflammation and fibrosis with no evidence of EMH. After bone marrow examination and molecular studies, the patient’s final diagnosis was myeloproliferative neoplasm, consistent with PMF.
The patient was first treated with hydroxyurea at a dose of 500 mg/day, which resulted in only mild improvement, and dose escalation to 1 g/day did not produce good control of lymphadenopathy and splenomegaly. Next, the patient was given 10 mg of ruxolitinib twice daily, resulting in a dramatic response and a marked reduction of both spleen and lymph node size.
“EMH in a lymph node is a potential diagnostic pitfall in such [cases,] as it could be mistaken for metastatic cancer…Furthermore, presence of EMH can be problematic especially when evaluating lymph nodes during frozen section where morphology is frequently less than optimal,” write the authors. While they emphasize that EMH is not always a malignant process, a patient who has EMH should always be examined for underlying bone marrow disorders, as it may be the first manifestation of an underlying case of PMF.
Aljabry MS, Asiri S, Elsafi T, Elyamany G. Generalized lymphadenopathy secondary to isolated extramedullary hematopoiesis as an initial manifestation of primary myelofibrosis. Hematol Rep. 2018;10(2):7588. doi: 10.4081/hr.2018.7588.