A woman notices what seems to be a strange growth on her arm. Hypochondriac that she is, she runs off to her dermatologist before the day is over. The doctor takes a graft from her arm and gives it a look under a microscope. The results are a relief: what she thought was cancerous turns out to have been her lunch. As the doctor put it (each dash is a letter):

"-- --------. --- -- - -----."

If you've got the answer, do post it in a comment.