Ocular histiocytic sarcoma in a cat.

A 13-year-old male neutered British blue cat presented with uveitis, hyphema, and dyscoria in the right eye. Light microscopic examination revealed that the ciliary body, iris root, drainage angle, and adjacent choroid were infiltrated by sheets of large neoplastic mononuclear and multinucleate round to polygonal cells. Neoplastic cells stained immunopositive for CD18 and HLA-DR (MHC class II) and were immunonegative for CD3, CD79a, MUM-1, CD117 (c-Kit), and S100.