If you cough up blood does it mean that you have throat cancer?

No: The most common cause for coughing up blood is a sore throat. The other common reasons are pneumonia, a pulmonary embolus (blood clot), lung cancer, throat cancer, tuberculosis.

Possibilities...: The most common etiology of hemoptysis, coughing blood, is bronchitis. But, malignancy, including in the throat, lung, etc., is another possibility. So, hemoptysis always requires a work-up to rule out malignancy. See your doctor if you are experiencing hemoptysis.