Maura Tierney's Breast Cancer

With her career in full swing and roles in multiple shows, 44-year-old 'ER' veteran Maura Tierney is dropping everything to undergo further treatment for breast cancer.

Tierney announced on Thursday that she was dropping out of NBC's new series 'Parenthood' in order to treat the disease, of which she claims her doctors are optimistic about the outcome.

Tierney also had a major role on the most recent season of FX's 'Rescue Me.'