Subcutaneous and hepatic myelolipomas in four exotic birds.

Abstract

Myelolipomas are benign extramarrow neoplasms that are composed of various proportions of fat and hematopoietic cells. These tumors are reported infrequently in human being~,’.*.’~ domestic and exotic cats,Io and dogsI4 but have not been reported in birds. The purpose of this brief communication is to report myelolipomas originating from the subcutis or liver in four exotic birds. All neoplasms were encountered over a 5-year period in routine surgical biopsy or necropsy tissues submitted to the Department of Veterinary Pathology and Athens Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia. An adult female saffron toucanet (Baillonius bailloni) died suddenly following a brief period of weakness. At necropsy, the liver appeared enlarged and had multiple white foci ranging from 2-3 mm to 1 cm in diameter. The presumptive clinical diagnosis was avian mycobacteriosis. A 4-year-old female society finch (Lonchura domestica) was submitted for examination of an elevated, broad-based, slowly enlarging, semisoft, 2x 2.5x I-cm subcutaneous mass over the right thigh. The size of the mass interfered with perching, balance, and limb movement. Neoplasia was suspected, and the bird was euthanatized. The only lesion observed at necropsy was the subcutaneous mass. On gross section, the mass appeared brownish yellow with a pale tan to white center. An adult hyacinth macaw (Anodorhynchus hyacinthinus) of undetermined sex was presented for examination of a slowly enlarging 3x 5x 2.5-cm dermal mass over the right thigh. A lipoma was suspected clinically, and the mass was surgically excised under general anesthesia. Recovery from anesthesia was uneventful, and tumor regrowth was not observed following surgical resection. On cut surface, the mass appeared circumscribed, soft, and pale off-white to yellow-brown. A 10-year-old male cockatiel (Nymphicus hollundicus) was presented for a slowly enlarging 4x 4x 3-cm mass over the left thorax. Neoplasia was suspected clinically, and surgical excision was attempted by the refemng veterinarian. The bird died from intraoperative hemorrhage. A necropsy was not performed; however, the excised subcutaneous mass was submitted for histopathologic examination. On cut surface, the mass was firm and yellow. All tissue specimens were preserved in 10% neutral buffered formalin, processed routinely, embedded in paraffin, sectioned at 3 pm, and stained with hematoxylin and eosin (HE). Liver sections from the toucanet also were stained for iron by Perl’s technique. Additional hepatic specimens from the toucanet were examined ultrastructurally for the presence of retrovirus and herpesvirus, which can induce various hemolymphatic neoplasms in poultry.’ Tissue was transferred from formalin to Trump’s fixative and processed routinely for transmission electron microscopy. Specimens were postfixed in osmium tetroxide, dehydrated in graded alcohols, embedded in Spurr plastic, sectioned, placed on formvar-coated copper grids, stained with uranyl acetate and lead citrate, and examined at 80 kVp. Table 1 contains a summary of the signalment of the four birds and some general characteristics of the myelolipomas. Upon gross inspection, all of the neoplasms were circumscribed to lobulated and soft to semisoft and had an appearance suggestive of adipose tissue with hemorrhage. Microscopically, the hepatic myelolipomas were clearly demarcated form the adjacent parenchyma but were unencapsulated (Fig. 1). In contrast, the subcutaneous neoplasms were encapsulated partially by a thin layer of connective tissue (Fig. 2). All neoplasms were composed of various percentages of lipocytes and hematopoietic cells. Within the