Mammary gland
neoplasms in macropods are uncommonly reported, and the morphological and immunohistochemical characteristics are incompletely described. The goal of this study was to describe the morphologic features of macropod
mammary neoplasms and to determine the molecular subtypes of mammary
carcinomas using a panel of
antibodies against
estrogen receptor (ER),
progesterone receptor (PR),
human epidermal growth factor receptor 2 (Her-2), p63, smooth muscle actin (SMA), and
epidermal growth factor receptor (EGFR). Biopsy and necropsy specimens were examined from 21 macropods with mammary
tumors submitted to Northwest ZooPath from 1996 to 2019. In accordance with the histologic classification of canine mammary
tumors proposed by Goldschmidt and colleagues, tubulopapillary (2), tubular (10), and comedo-
carcinomas (2),
adenoma (1), lobular
hyperplasia (3), fibroadenomatous
hyperplasia (1), and
mastitis (2) were diagnosed. Red kangaroos (Osphranter rufus) were most commonly diagnosed with mammary
carcinomas (79% of all
carcinomas). Seven
carcinomas had lymphovascular invasion and 2 also had pulmonary
metastases. Six of these 7
carcinomas were classified as grade 3. Immunohistochemistry (IHC) for all
antibodies was performed on 9/14
carcinomas, and partial IHC was performed for 3 cases. All 12
carcinomas were immunoreactive for PR, 5 for ER, 9 for EGFR, and none for Her-2. Five of the 9 mammary
carcinomas with complete IHC data were classified as
luminal A subtype, and 4 were normal-like subtype. Accurate classification of mammary
tumors in macropods based on morphology, immunohistological characteristics, and molecular subtype may be helpful in guiding clinical management, prognosis, and potential therapeutic targets.