The Collaborative International Dictionary of English v.0.48:

Lymphoma \Lym*pho"ma\, n. [NL. See Lymph, and -oma.] (Med.)
   A tumor having a structure resembling that of a lymphatic
   gland; -- called also lymphadenoma.
   [1913 Webster]

   Malignant lymphoma, a fatal disease characterized by the
      formation in various parts of the body of new growths
      resembling lymphatic glands in structure.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lymphoma
    n 1: a neoplasm of lymph tissue that is usually malignant; one
         of the four major types of cancer