Tina is 34 years old and has been suffering with bloody diarrhoea and abdominal cramps for the past 8 weeks. She has noticed some weight loss and reduced appetite. On further questioning there is mucus in her stool and she has been opening her bowels overnight which is unusual for her. She works in real estate and has become increasingly tired recently. She takes Microgynon for contraception but has no other medical problems. She has not changed her diet recently and there is no family history of cancer.
On examination, her vital signs are stable and abdominal and rectal examination are unremarkable.
What is the most likely diagnosis?