Acute Granulocytic Leukemia in a Slaughter Goat

A 14-month-old crossbred goat was presented for slaughter at a federally inspected slaughter plant. On antemortem inspection, the goat was thin with no other abnormalities. Gross findings on postmortem examination included splenic enlargement (5 x normal), green proliferative tissue extending from the pericardial surface, fibrous epicardial tags, and variable enlargement of all lymph nodes with inguinal lymph node hemorrhage and greenish discoloration of a purulent exudate. The liver was discarded before inspection. The kidneys appeared normal grossly. Samples of kidney, lung, spleen, heart, muscle, pericardium, bone marrow (sternum), and lymph nodes were fixed in 10% neutral buffered formalin and shipped to the US Department of Agriculture, Pathology Division, Athens, Georgia, for histopathologic examination. Tissues were routinely processed, embedded in paraffin, sectioned at 4 μm, and stained with hematoxylin and eosin. Formalin-fixed lymph node, spleen, and pericardial tissue were further processed by sectioning into 2-3-mm cubes, rinsing for 1 hour in distilled deionized water, and postfixing in picric acid fixative Figure 1. Lymph node; goat. Granules within promyelocytes (2% glutaraldehyde, 2% paraformaldehyde, 0.2% picric acid (arrow). Bar = 10 μm. in 0.1 M cacodylate buffer). These tissues were then routinely processed and sectioned for transmission electron microscells and promyelocytes predominating) and increased maccopy. rophage activity. Significant histologic findings were limited to the lymph Transmission electron microscopic examination of perinodes, pericardial tissue, pleural adipose tissue, spleen, and cardial tissue revealed a consistent population of neoplastic bone marrow. Lymph nodes exhibited variable replacement cells with granules typical of primary (electron dense, large, of normal architecture and invasion of perinodal fat by large oval to elongate), secondary (more granular center with no cells with hyperchromatic nuclei with coarse stippled or veelectron dense core), and tertiary (bacilliform) granules of sicular chromatin and, rarely, a small eosinophilic nucleolus. neutrophils. 6 Nuclei were indicative of juvenile and myeloThese cells had scant to moderate lightly basophilic cytocyte levels of differentiation with dispersed chromatin, scant plasm with variably distinct borders. There were 1 or 2 michromocenters, and primitive nucleoli (Fig. 2). Occasional totic figures per 40 x field of view. Admixed with these cells mature eosinophils had large granules containing central were cells with round to band-shaped nuclei with marginated crystalloids (Fig. 3). chromatin and 1 or 2 darkly basophilic chromocenters. These cells also had moderate to abundant homogeneous eosinophilic cytoplasm with distinct eosinophilic granules (Fig. 1). Smaller numbers of mature neutrophils and occasional eosinophils were admixed with these cells. Prominent single cell necrosis and scattered, occasionally confluent areas of hemorrhage with necrosis were observed. Pericardial tissue (adipose) and pleural adipose tissue were similarly infiltrated and expanded. The spleen was markedly congested with marked extramedullary hematopoiesis (megakaryocytes, nucleated red blood cells). There were rare myelocytes or juvenile granulocytes within sinuses. The bone marrow was markedly hypercellular with granulocytic hyperplasia (blast