Proventricular hemangiosarcoma identified in a broiler at slaughter

A discrete circumscribed red nodule present on the surface of the proventriculus of a 7-week-old broiler was diagnosed as a hemangiosarcoma. Histologically, discrete islands and dense sheets of anaplastic ovoid to spindle-shaped basophilic cells surrounded irregular vascular clefts and spaces. Mitotic figures were focally numerous, and extension into the tunica muscularis of the proventriculus was seen. Neoplastic islands were also present in the tunica mucosa and the adjacent mesentery.