Endoscopic ultrasound guided fine-needle aspiration of a splenic hemangioma with extramedullary hematopoiesis.

Extramedullary hematopoiesis (EMH) is the production of mature blood elements outside of the bone marrow and can occur as a compensatory result of a marrow replacing process or from marrow space occupying lesions such as tumor or marrow fibrosis. EMH can also be induced by factors elicited by neoplasms, such as vascular endothelial growth factor (VEGF). Usually, EMH is a diffuse process most commonly observed in lymph nodes, liver, and spleen. Rarely, EMH can form a mass lesion. Although the spleen is a common site for diffuse EMH, it is a rare location for a mass forming EMH. Hemangiomas are the most common benign tumors of the spleen. A case of a discrete, 8 cm lesion was noted incidentally on CT scan in a 59-year-old man with no significant past medical history. Endoscopic ultrasound guided fine-needle aspiration (EUS FNA) biopsy was performed and cytologic examination revealed trilinear hematopoiesis, with the most distinctive elements being megakaryocytes and erythroid precursors. A diagnosis of EMH was made. On resection, the mass was a hemangioma with EMH. EUS guided FNA is a useful tool for diagnosing splenic masses. Awareness of EMH, both as a mass forming lesion and a feature associated with benign and malignant vascular lesions is important, especially in patients with hematologic malignancies or marrow replacing processes.