Ingluvial squamous cell carcinoma in a game chicken.

A 4.5-yr-old rooster was presented for a "lump on the neck." The bird exhibited dyspnea immediately prior to death. Necropsy revealed a crateriform lesion in the crop. Histologically, the lesion was diagnosed as an invasive squamous cell carcinoma, extending almost the entire thickness of the crop. Polymerase chain reaction and ultrastructural examination failed to identify a viral component. Early vascular invasion was identified.