Arterial, venous and lymphatic pathways in dorsal mucosa of dog tongue (implicated routes for metastatic lesions).

Because metastatic lesions of the tongue are known to spread primarily via lymphatics and secondarily via veins, it would seem likely that knowledge of their distribution would be essential to clinico-pathologic interpretation. Although there is unaminity of opinion regarding lymphatic afferent pathways from the tongue to regional lymph nodes, unanimity of opinion is lacking regarding distribution of lymphatics and veins in the dorsal mucosa. Pivotal questions are: Do lymph vessels in the dorsal lingual mucosa extend across lines of fusion of embryonic lingual processes (lingual raphe and sulcus terminalis)? Do anterior and posterior portions of the tongue drain separately? To resolve these problems and to clearly delineate arteries, veins and lymphatics, each vessel type was perfused with a different colored perfusate. Imaging techniques provided by perfusion methods demonstrated precisely that the lymphatic network extends uniformly throughout the mucosa from tip to base crossing the sulcus terminalis in route and from border to border crossing the median lingual raphe. Mucosal veins are peltate in form anteriorly, but are pennate in form forward to the vallate papillae. The distribution characteristics of these vessel types provides opportunities for multidirectional spread of metastatic lesions. Because spread via both routes is rapid and multidirectional, it becomes clear that chemotherapy and radiotherapy may be preferable to surgery. The latter is frequently mutilating and sometimes the patient is left without capabilities of phonation and deglutition. Furthermore, radical surgical procedures do not provide assurance that the patient has been entirely separated from the malignancy.