Final answer:
Hodgkin's disease is the malignancy of the lymphatic system mentioned in the question, and it is a type of lymphoma.
Step-by-step explanation:
The malignancy of the lymphatic system referred to in the question is known as Hodgkin's disease. This is a type of lymphoma, which is a form of cancer where masses of malignant T and/or B lymphocytes collect in the lymph nodes, spleen, liver, and other tissues. This is different from leukemia, which is a cancer involving an abundance of leukocytes.
The other conditions listed, such as cystic fibrosis, Martin-Bell Syndrome, and leukocytosis, are not malignancies of the lymphatic system. Cystic fibrosis is a genetic disorder affecting the lungs and digestive system, Martin-Bell Syndrome, also known as fragile X syndrome, is a genetic condition causing intellectual disability, and leukocytosis is a condition involving an abnormally high number of white blood cells but is not a cancer.