Myelolipoma

This rare neoplasm has been described in both the dog and cat, but reported involvement of the liver is limited to the cat (McCaw et al., 1990; Kamiie et al., 2009). Myelolipomas form as a nodular mass composed of islands of hematopoietic precursors and adipocytes. Cytologically, large amounts of morphologically unremarkable adipocytes and a population of erythroid, myeloid, and megakaryocytic precursors are present. Distinction of myelolipoma from EMH can be challenging. Extramedullary hematopoiesis is frequently seen as a diffuse lesion with abundant amounts of hepatocytes also present on the slides, while myelolipoma is commonly diagnosed from a nodular mass with abundant immature and mature hematopoietic cells and minimal liver tissue.