Brown spotting between periods is often a sign of irregular menstrual cycles. It may also be a sign of endometrial or cervical cancer according to WebMD.com.
Often associated with old endometrial tissue, a brown discharge should not necessarily be a cause for concern. This discharge may occur in the middle of the menstrual cycle when a woman is ovulating. The discharge may also be caused by menopause, pelvic inflammatory disease or sexual transmitted diseases such as gonorrhea.
Sometimes a brown discharge is accompanied by other symptoms, which may include pain, burning, itching, vaginal dryness, frequent urination or pain during intercourse.