SMALL ANIMAL CYTOLOGIC DIAGNOSIS by Anne M. Barger and Amy L. MacNeill

Author:Anne M. Barger and Amy L. MacNeill
Language: eng
Format: epub
Publisher: CRC Press

Extramedullary hematopoiesis

Embryologic hepatoblast cytokine production induces the niche necessary to make liver the first site of hematopoietic production (Sugiyama et al., 2011). Under conditions of increased hematopoietic need in the adult, this capacity is revived and manifests as development of both erythroid, myeloid, and/or megakaryocytic cell proliferation associated with resident Kupffer cells (Figures 9.23A–C; Otsuka et al., 2011). Although the cytologic diagnosis of extramedullary hematopoiesis (EMH) can be made based on the presence of any one hematopoietic cell line with complete maturation outside the bone marrow, EMH of more than one cell line will commonly be observed in the same patient. EMH, like lipid and glycogen accumulation, is a fairly nonspecific finding. It should be considered a secondary change and an aid to help define the nature of the primary problem. Care should be taken to ensure that the sample is truly representative of liver, as incidental aspiration of the spleen during hepatic FNA is common (colloquially termed a ‘spliver’ sample by the authors) and the spleen is a more common site of EMH. Hepatic EMH produces a multifocal to diffuse lesion ultrasonographically and therefore a higher cytologic accuracy for this entity could be predicted; however, data hint at potentially low positive and negative predictive values in small study populations (Warren-Smith et al., 2012; Bahr et al., 2013). Myelolipoma is an uncommon tumor, which presents as a nodular lesion with bone marrow elements and adipocytes cytologically. Myelolipoma can be challenging to distinguish from EMH by aspiration alone.

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