Follicular thyroid carcinoma in a domestic pigeon (Columba livia)

A 10-year-old female domestic pigeon (Columba livia), presented with marked depression, hyporexia, and scant green droppings for approximately two weeks, according to the owners. On general physical examination, a nodule was detected in the subcutaneous tissue at the level of the crop. Due to the bird´s poor prognosis, euthanasia was performed. At necropsy, an oval mass was found in the subcutaneous tissue of the ventral region of the distal third of the neck, located above the crop and adjacent to the trachea. The mass measured 3.5 x 2.2 x 1.5 cm, was light brown, had a slightly irregular and firm consistency, and on cut section showed small cavitations. The tissue was submitted to Departamento de Patología, Facultad de Medicina Veterinaria y Zootecnia, UNAM, for histological evaluation, where it was diagnosed as follicular thyroid carcinoma. In birds, thyroid neoplasms have been reported as incidental findings and their prognosis is usually poor. Antemortem diagnosis is difficult because birds tend to show nonspecific clinical signs; therefore, in most cases, the definitive diagnosis is made postmortem. Although papillary thyroid adenomas have previously been reported in pigeons, the aim of the present study is to report the first case of follicular thyroid carcinoma in a domestic pigeon.