A dermal vascular hamartoma in a sun conure (Aratinga solstitialis).

Abstract: A 19-month-old sun conure (Aratinga solstitialis) of undetermined sex was examined for feather picking of the cranial ventral thoracic region and a lump on the right shoulder. An irregular dermal mass present on the dorsal aspect of the bird's right shoulder was surgically removed. On the basis of histopathologic, histochemical, and immunohistochemical examination, the mass was determined to be a cutaneous vascular hamartoma.

Key words: cutaneous vascular hamartoma, vascular anomaly, skin, avian, sun conure, Aratinga solstitialis

Clinical Report

A 19-month-old sun conure (Aratinga solstitialis) of undetermined sex and weighing 107 g was presented for examination with a 2-month history of feather picking on its chest and a lump over the right shoulder. The bird was housed in a wire cage (91 x 76 x 76 cm [36 x 30 x 30 in]) with several perches, a fleece cave, and a newspaper substrate. A commercial pelleted conure diet, bran flakes, peeled grapes, and fresh water were provided.

On physical examination, an irregular dermal mass was observed on the dorsal right shoulder, and feather loss was present over the sternum. No other physical abnormalities were observed. A blood sample was obtained for a complete blood cell count and plasma biochemical analysis. Hypophosphatemia (3.1 mg/dl) was the only abnormality noted on results.

The bird was anesthetized with isoflurane administered by face mask, and the shoulder area was surgically prepared. A bright pink, lobulated dermal mass (approximately 1.0 x 0.5 x 0.75 cm) on the dorsal aspect of the right shoulder and overlying integument was resected and submitted for histopathologic examination. The wound was closed routinely with 3 absorbable skin sutures. The bird was given fluids subcutaneously (lactated Ringer's solution, 1.5 ml) postoperatively. No analgesics were administered. The bird recovered from the procedure and anesthesia uneventfully. On discharge from the hospital, the owner was instructed to restrict the bird's activity, keep the bird confined to the cage, and observe for picking at the surgical site. Three days later the owner reported the bird was doing well and the breast feathers were regrowing. To date, there is no report of regrowth.

Formalin-fixed tissues were prepared by standard techniques and stained with hematoxylin and eosin. On histologic examination, a multilobulated, irregularly spaced, multinodular, hypercellular mass was present throughout the superficial dermis. The lobules contained variably sized proliferating vascular structures including capillaries, venules, and arterioles frequently associated with medium-sized arteries (Figs 1 and 2). Many contained erythrocytes within the lumen. Masson trichrome stain, used to distinguish muscle from collagen, marked the muscular walls of the vascular structures of the mass the same as normal arteries within the section, as well as the arterial walls of the external control. Standard indirect streptavidin-biotin immunoperoxidase techniques were performed on paraffin-embedded samples to confirm the vascular identity of the structures. Antibodies to actin and factor VIII-related antigen were used to confirm the presence of vascular smooth muscle and endothelial cells, respectively. Normal blood vessels within the tissue samples served as internal positive controls.

[FIGURES 1-2 OMITTED]

The cells lining all the vascular structures of the mass, as well as the normal blood vessels of the sample and the vasculature of the external control, stained positively with factor VIII-related antigen (Fig 3). Similarly, the muscular walls of the vascular structures of arterial character in the mass and normal arteries all stained positively with the smooth muscle actin antibody (Fig 4). The diagnosis of cutaneous vascular hamartoma was made on the basis of the histologic, histochemical, and immunohistologic features.

[FIGURES 3-4 OMITTED]

Discussion

A hamartoma is defined as a focal malformation that grossly and microscopically resembles a neoplasm, resulting from either a faulty development in an organ, an abnormal mixture of tissue elements, or an abnormal proportion of a tissue element normally present in that site. (1) These are frequently present at birth and can develop and increase in size at the same rate as normal components as the individual grows. Vascular hamartomas are usually congenital anomalies comprising malformations of capillaries; venous, arterial, or lymphatic channels; or various combinations of these. To our knowledge, this is the first report of a hamartoma comprising various vascular structures within the dermal tissues in a psittacine bird.

Vascular lesions generally result from congenital anomalies, inflammatory diseases, or neoplastic processes. Vascular anomalies are fairly common in people and can be present in up to one half of the general population. Hemangiomas, vascular tumors with a characteristic rapid growth phase of endothelial proliferation followed by a slow involution phase, are the most common benign soft tissue tumor of childhood. Vascular malformations are also very common. (2,3) These are structural malformations of fully formed vasculature at birth that are relatively static and composed of capillaries, veins, arteries, lymphatics, or combinations thereof and that possess normal endothelial turnover and never involute.

Congenital or juvenile vascular neoplasms in animals are uncommon to rare and have infrequently been reported in birds. Published reports include horses, (4-6) pigs, (7) cattle, (8) and broiler chickens. (9) Vascular neoplasia has been associated with retrovirus infection in young chickens. (10,11) Hemangiomas in birds occur in the subcutis, spleen, liver, kidney, and testicular capsule. (12,13) Hemangiosarcomas occur in the skin, liver, lungs, spleen, muscle, mesentery, kidney, heart, oviduct, bone marrow, myocardium, and bone or synovium. (13,14) Individual case reports of hemangiosarcomas in older birds include an Amazon parrot (Amazona farinosa), (15) a golden pheasant (Chrysolophus pictus), (16) and a budgerigar (Melopsittacus undulatus). (17)

Vascular anomalies are also uncommon to rare in animals and have not been reported in birds. Vascular anomalies of the central nervous system have been reported with the greatest frequency. They occur in dogs, (18-20) calves, (21) cats, (22) goats, (23,24) and foals. (25) Cutaneous hamartomas in the scrotum of dogs, (26) the face of a thoroughbred horse, (27) and the hip of a Saanan goat (23) have been reported. Hamartomas of vascular origin have also been described in the skin (28) and livers of cattle (29) and dogs, (30) the ovaries and testicles of cattle, (31,32) the ovary of a horse (33) and pigs, (34) the gingiva of cows (35,36) and a cat, (37) muscle (38) and lungs (39) in dogs, and tendon sheaths in horses. (40)

To our knowledge, this case represents the first report of a presumably congenital vascular hamartoma in a bird.

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From the Department of Pathobiological Sciences (Steinberg) and the Department of Surgical Sciences (Paul-Murphy), School of Veterinary Medicine, University of Wisconsin, Madison, 2015 Linden Drive, Madison, WI 53706, USA; and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University (Pare), College Station, TX 77843, USA.