A “Swiss kiss” is a white mark located typically behind the neck, but may be a part of the neck. A full ring would not meet type standard. The AKC breed standard lists, as disqualifications, blue eye color, and any ground color other than black. The breed standard for the Bernese mountain dog states that dogs should not be 'aggressive, anxious or distinctly shy', but rather should be 'good-natured', 'self-assured', 'placid towards strangers', and 'docile'. He only attacks if really needed (his owners getting attacked). The temperament of individual dogs may vary, and not all examples of the breed have been bred carefully to follow the standard. Bernese Mountain Dogs are killed by many types of cancer, including malignant histiocytosis, mast cell tumor, lymphosarcoma, fibrosarcoma, and osteosarcoma. Inherited medical problems that a Bernese Mountain Dog may face include malignant histiocytosis, hypomyelinogenesis, progressive retinal atrophy, and possibly cataracts and hypoadrenocorticism.