Lymphoma is actually what we usually refer to as lymphatic cancer; they are in fact the same disease. When we talk about cancer, it generally refers to malignant tumors that occur in epithelial tissues, and we call them cancer, such as lung cancer, intestinal cancer, nasopharyngeal cancer, etc. Lymphoma, however, is also a type of malignant tumor, but it typically occurs in the lymph nodes, or malignant tumors of some extranodal tissues or organs, which we refer to as lymphoma. It's called differently simply because it arises from different locations and tissues; lymphoma is essentially what is commonly known as lymphatic cancer.