The occurrence of estrogen and progestin receptors and anti-estrogen binding sites (AEBS) in canine non-Hodgkin's lymphomas.

In the present study the occurrence of estrogen and progestin receptors in the lymphoid tissue of 20 canine non-Hodgkin's Lymphoma patients was investigated. Lesions in all dogs were histologically classified according to criteria used in human patients. No progestin receptors could be demonstrated. Estrogen receptors were found only in the cytosol of two canine lymphomas. Antiestrogen binding sites were present in all 18 cases examined (range 37-356, median 110 fmol/mg protein). No correlation with age, sex or histological classification was found. A pilot study was carried out in five of these dogs that were negative for estrogen receptors and positive for antiestrogen binding sites. These dogs were treated with the antiestrogen tamoxifen (20-30 mg/day) for 2-3 weeks, but the treatment had no apparent effect. It was concluded that if antiestrogens do play a role in the treatment of non-Hodgkin's lymphoma in the dog, it is most likely not by means of antiestrogen binding sites.