Sayyidah Aishah (may Allah be pleased with her) said that Fatimah bint Abi Hubaysh (may Allah be pleased with her) said: O Messenger of Allah! I suffer from istihadah (prolonged bleeding) and do not become pure; shall I then leave the prayer? The Prophet (peace and blessings be upon him) said: "That is only the blood of a vein, not menstruation. When the menstruation comes, leave the prayer, and when it ends, wash off the blood and take a ritual bath (ghusl), then pray."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21256