Fine-needle aspiration cytology of extramedullary hematopoiesis (myeloid metaplasia).

Myeloproliferative disease may be associated with extramedullary hematopoiesis (EH). Clinically, however, the differential diagnosis of solid masses in these patients includes not only EH but also inflammatory lesions and malignant neoplasms, including granulocytic sarcoma. We report the fine-needle aspiration (FNA) cytology of extramedullary hematopoiesis in five patients with a history of myeloproliferative disease. All of the masses developed subsequent to the diagnosis of myeloproliferative disease. Two of the patients had chronic myelogenous leukemia, one had essential thrombocythemia, and two had an unspecified chronic myeloproliferative disorder. The patients ranged in age from 50 to 88 years, and all presented with solid masses involving the kidney (two aspirates), liver (one aspirate), and lymph nodes (three aspirates). One of the lymph node aspirates was from a paratracheal lymph node. Cytologically, the lesions were composed of varying numbers of hematopoietic cells from all three hematologic cell lines. The Diff-Quik stain was especially helpful in the recognition of the hematopoietic cells such as granulocytic precursors, eosinophils, and megakaryocytes. In several cases, the megakaryocytic component was particularly prominent. In one case, the Factor VIII immunoperoxidase stain was used to confirm the megakaryocytic lineage of the multinucleated cells. The cytologic differential diagnosis, which includes granulocytic sarcoma, inflammatory disorders, and other lesions containing multinucleated giant cells, is discussed.