Extraskeletal osteoma in a canary (Serinus canaria)

Abstract

Osteoma is an uncommon bone tumor in avian species and other animals. A 2-year-old male canary (Serinus canaria) with a history of an oval mass in the left wing for several months was examined. Radiographs showed a radio-opaque mass. Upon the bird's owner request, the canary was euthanatized and submitted for necropsy. The histopathologic examination revealed numerous trabeculae consisting of both woven and lamellar bone covered by one to several rows of normal osteoblasts. The trabeculae were closely packed, having only small intertrabecular spaces which contained proliferating osteoblasts, sinusoids and myeloid tissue. Based on clinical, radiographic, and histopathologic findings, the mass was diagnosed as extraskeletal osteoma. To the best of authors' knowledge, extraskeletal osteoma has not been reported in in avian species so far, and this is the first report of osteoma tumor in the birds. However, benign tumors of bones are extremely rare in the birds, osteoma should be considered as a differential diagnosis in the birds with bone lesions.

Keywords: Avian; Canary (Serinus canaria); Extraskeletal osteoma; Histopathology.

Fig. 1

A) The encapsulated oval bony mass (arrow) approximately 12 × 8 × 6 mm is observed on the left wing of a Serinus canaria; B) Radiograph of the left wing shows a regularly ovoid, radio-opaque mass in the forearm region.

Fig. 2

Closely-packed woven bone (W) with small inter-trabecular spaces (stars) surrounded by a periosteum (P), (H & E; Bar = 220 μm

Fig.3.

A) Numerous trabeculae consisting of woven bones (W), (H & E; Bar =80 μm); (B) Osseous trabeculae covered by a row of osteoblast with normal appearance (arrows), (H & E; Bar = 20 μm

Fig. 4

Small intertrabecular spaces contained proliferating osteoblasts, sinusoids and myeloid tissue which varied in amount (H & E; Bar = 220 μm