The Collaborative International Dictionary of English v.0.48:

Mastodynia \Mas`to*dyn"i*a\, Mastodyny \Mas*tod"y*ny\, n. [NL.
   mastodynia, fr. Gr. masto`s the breast + ? pain.] (Med.)
   Pain occuring in the mamma or female breast, -- a form of
   neuralgia.
   [1913 Webster]