The Collaborative International Dictionary of English v.0.48:

Sarcoma \Sar*co"ma\, n.; pl. L. Sarcomata (# or #), E.
   sarcomas. [NL., from Gr. ?, from sa`rx, sa`rkos, flesh.]
   (Med.)
   A tumor of fleshy consistence; -- formerly applied to many
   varieties of tumor, now restricted to a variety of malignant
   growth made up of cells resembling those of fetal development
   without any proper intercellular substance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sarcoma
    n 1: a usually malignant tumor arising from connective tissue
         (bone or muscle etc.); one of the four major types of
         cancer