Animal ID: 8 years old, male, Staffordshire Bull Terrier dog.

Organ: Formalin-fixed spleen specimens following total splenectomy.

Clinical findings: In the routine examination, abdominal swelling was noticed by the referring veterinarian and an enlargement of the spleen was determined as a result of ultrasonography. The animal’s hemogram and biochemical findings were within normal limits. Post follow up revealed that the animal is healthy with no sign of diseases.

Macroscopic findings: Splenomegaly accompanied by large and small sized nodular structures. Cross section of the spleen showed in yellow color due to the presence of fat cells in some areas (Figs 1 and 2).

Cytological findings: Benign adipocytes were seen together with many hematopoietic precursor cells. It was noted that
hematopoietic cells are cells from the myeloid, erythroid and megakaryocytic series of the normal bone marrow (Fig 3).

Histopathological findings: Well differentiated, mature adipocytes were distributed diffusely in the spleen parenchyma along with normal- appearing megakaryocytic cells and other hematopoietic precursor cells from myeloid, erythroid series (Figs 4 and 5).

Hemosiderin pigment laden macrophages were detected in the subcapsular areas. In addition, the spleen capsule, which was thickened in some areas with fibrosis were merged with sclerotic trabeculae of the spleen. In some areas, adipocytes were either merged or were necrotic, and foreign body giant cells were seen in these regions (Fig 6). White pulp was not detected in the spleen parenchyma. Diffuse haemorrhage and necrosis in the spleen were noted as well.

Diagnosis: Splenic myelolipoma.

Differential diagnosis: Hematoma, extramedullary haematopoiesis, lipoma without hematopoietic tissue, liposarcoma, mesenchymal tumors with three or more components lymphoid hyperplasia and tumors.

References:

Boes KM, Durham AC. Bone marrow, blood cells, and the lymphoid/lymphatic system. In: James F. Zachary; Editor, Pathologic Basis of Veterinary Disease, 6th Edition, Elsevier Inc., pp.724-804, 2017.

Linder KE. Tumors of the spleen. In: Donald J Meuten, Editor, Tumors in Domestic Animals. 5th edition, John Wiley & Sons Inc., pp.307-321, 2017.

Valli VEO, Kiupel M, Bienzle D, Wood RD. Hematopoietic system. In: M.Grant Maxie, Editor, Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, 6th Edition, vol.3, Elsevier Inc., pp.102-268, 2016.

Archive Material: Ondokuz Mayis University, Faculty of Veterinary Medicine, Department of Pathology, Samsun, Turkey

Block ID: 215/20

Referring Clinic: Çağatay Veterinary Clinic, Bodrum, Muğla, Turkey

Macroscopy:

• • Fig 1. Nodular splenomegaly.
  • Fig 2. Yellowish appearance due to lipoid material in the fixed tissue sample.

Cytology:

• • Fig 3. Myeloid and erythroid cells along with mature adipocytes. Giemsa staining.

Histopathology:

• • Fig 4. Adipocytes and megakaryocytic, erythroid and myeloid precursors, Haematoxylin-eosin.
  • Fig 5. Adipocytes and megakaryocytic, erythroid and myeloid precursors, Haematoxylin-eosin.
  • Fig 6. Multinucleated giant cells formed against lipoid material released from ruptured adipocytes, Haematoxylin-eosin.