Complex carcinoma of the mammary gland in a free-living Japanese raccoon dog (Nyctereutes procyonoides viverrinus).

A complex carcinoma of the mammary gland was diagnosed in a free-living old female Japanese raccoon dog (Nyctereutes procyonoides viverrinus). Invasion into lymphatic vessels and metastasis in the inguinal lymph node were observed. This is the first report of complex carcinoma of the mammary gland in a raccoon dog.