20 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
LYMPHANGIOMA 
Lymphangiomas are neoplasms consisting of dilated lymph vessels 
or lymph spaces. They are either acquired or more often congenital 
in man. In domestic animals they are unimportant and rarely 
found. Several cases of lymphangioma have been reported in the 
pleura, pericardium, and heart in horses and as superficial skin 
changes about the nipples in cats. It is often difficult to separate 
dilations of lymphatic channels due to obstruction from hyperplastic 
processes. The dilated lymph vessels usually preserve the original 
channels, as in lymphangioma simplex, or the number of the lymph 
vessels may be increased and their spaces enlarged, as in lymphan- 
gioma cavernosum ; or the lymph spaces may form cystic dilations, as 
in the cystoid lymphangiomas. 
Among the congenital lymphangiomas of man may be mentioned 
macroglosia, a congenital enlargement of the tongue, macrochilia, 
the enlargement of the lips, and nevus lymphaticus of the skin. 
Dilated lymph channels are accompanied by stasis of the lymph 
caused by the presence of a parasite, Filaria sanguinis, which pro- 
duces a hyperplastic process in the skin that is known as elephantiasis 
or diffuse fibromatosis. This condition is sometimes found in horses 
and should not be taken for a neoplasm. 
LYMPHOMA 
Definition. — The name " lymphoma " designates a progressive 
proliferation of lymphadenoid tissue. The enlargement of lymph 
glands constitutes a debated subject in pathology. Formerly the 
name of lymphoma was used indiscriminately for all enlargements 
of lymphatic tissues independently of their cause. 
Seats. — Lymphomas start in any of the lymphoid tissues, which 
are so widely distributed in the animal economy. They frequently 
have their genesis in the lymph follicles or nodes found in mucous 
membranes, and in the compound lymphadenoid structures, as the 
lymph glands. They are found in the course of lymph vessels, or in 
the spleen, the red bone marrow, and thymus glands. These lym- 
phoid tissues are regarded as the parent source of leucocytes and 
lymphocytes, and are therefore affected by disturbances of the cir- 
culation and blood disorders. Lymphatic tissue reacts most readily 
to infective agents in all diseases of a septic and infectious nature. 
Any irritant that is responsible for an acute or chronic disease 
produces enlargement of the lymphadenoid tissues. 
Conditions resembling lymphoma. — Inflammatory enlargements of 
the lymphoid tissues are not true neoplasms. It is often very difficult 
to differentiate between them. 
Acute inflammation of the lymph glands which is manifested in 
the hyperplastic or in the exudative form is common in man and 
very common in domestic animals. The chronic form is as common 
in man as in the lower animals. The lesions may occur in a single 
node, but are more frequently found in several nodes of the same 
group, or in groups situated in different parts of the body. Tuber- 
culous lymphadenitis is the most frequent of these lymph-gland en- 
largements in domestic animals, especially in cattle and hogs. The 
lymph glands are enlarged, often contain hemorrhagic areas, may 
