Extramedullary hematopoiesis in the prostate.

A case of bone marrow myelofibrosis with extramedullary hematopoiesis in the prostate gland is described. This 75-year-old man had an 8-year history of myelofibrosis, massive hepatosplenomegaly, and progressive anemia and a 5-year history of bladder outlet obstruction symptomatology. Transurethral resection of prostate was performed, and light microscopic examination of the prostatic chips revealed a diffuse distribution of atypical megakaryocytes, immature granulocytes, and normoblasts in the prostatic stroma. The prostatic glandular epithelium was uninvolved. Immunostaining for hemoglobin in erythroid precursors and a chloroacetate esterase stain for granulocytic precursors were useful in confirming the diagnosis and in defining the extent of prostatic involvement. Extramedullary hematopoiesis is a rare process in the prostate gland, but it should be included in the differential diagnosis of cellular prostatic stromal lesions, particularly when atypical giant cells are observed.