206 Brief Communication

laminated appearance. The wall is infiltrated irregularly in most areas by large numbers of mixed inflammatory cells, predominantly heterophils and macrophages. In addition, the wall may be edematous. In our study, multiple masses were present and all conformed to this appearance. The smallest was approximately 2 mm in diameter and the largest approximately 15 mm in diameter. The rate of growth can be rapid with masses reaching 1 cm in diameter in one month. In the past these structures have been designated as cysts of the feather follicle; however, we feel they should be considered benign neoplasms of follicular cells which are forming microscopic feather-like structures. This is based on the complexity of the wall of the cystic mass with a demonstrable proliferative component, and on the similarity of these masses to the common benign hair follicle tumors of dogs, such as trichoepithelioma and pilomatricoma. Thus, we prefer the term feather folliculoma. In our experience the masses are most commonly seen in orange canaries; inbreeding for this particular color pattern may predispose to the development of these skin masses. Feather folliculomas may be large, may become multiple, and may result in incapacitation of the bird. They are amenable, however, to resection with no evidence of recurrence or metastasis