Malignant tumours are generally named according to their tissue origin.
Malignant tumours that occur in epithelial tissue, called carcinomas, invade the lymphatic vessels from the primary site, reach the lymph nodes and continue to grow, forming the same type of tumour as the primary cancer (metastatic lymph node cancer).
Malignant tumours of mesenchymal tissue origin are called sarcomas.
Lymphoma, on the other hand, is a malignant tumour of lymphopoietic tissue origin.
Thus lymphoma and lymphoma, with different tissue sources, are diagnosed and treated differently accordingly.