A primary extranodal lymphosarcoma causing recurrent episodes of dyspn
ea and exercise intolerance is described in a 13-year-old cat. The aff
ected segment of the tracheal wall was markedly thickened due to trans
mural infiltration of monomorphic neoplastic lymphoid cells and the lu
men was severely compressed. The diagnosis was based on light microsco
pic studies, positive immunostaining for feline IgA, and special stain
s.