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Papillary ductal adenocarcinoma in the mammary glands of two horses
  1. G. P. Reppas, BVSc, DipVetPath, FACVSc, MRCVS1,1,
  2. S. A. McClintock, BVSc, MVetClinStud, MACVSc1,
  3. P. J. Canfield, BVSc, PhD, MRCPath, FACVSc, MRCVS2 and
  4. G. F. Watson, MBBS, FRCPA3
  1. 1 Rural Veterinary Centre, Department of Animal Health, University of Sydney, Camden, New South Wales 2570, Australia
  2. 2 Department of Veterinary Pathology, University of Sydney, Sydney, New South Wales 2006, Australia
  3. 3 Department of Anatomical Pathology, Royal Prince Alfred Hospital, Missenden Road, Camperdown, New South Wales 2050, Australia


Mammary gland neoplasms in horses are uncommon and may initially be confused with mastitis. Masses from the mammary glands of two horses with chronic discharges were examined by cytology and histopathology. Both masses were diagnosed as papillary ductal adenocarcinomas with extensive intraductal and intralobular involvement and only focal infiltration of the adjacent stroma. Complementary immunohistochemical studies were made of both fresh and formalin-fixed tumour tissue, and attempts were made to assess the steroid receptor status of fresh tissue biochemically to assess the possibility of hormonal treatment as an adjunct to surgery. The results of these tests for oestrogen and progesterone receptors were negative.

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  • Mr Reppas's present address is 304-3 10 Horsley Road, Horsley Park, New South Wales 2164, Australia

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