It is narrated from Aishah (may Allah be pleased with her) that Fatimah bint Abi Hubaysh (may Allah be pleased with her) came to the Prophet (peace and blessings be upon him) and said: I suffer from istihadah (prolonged non-menstrual bleeding) and I do not become pure; should I abandon the prayer? He (peace and blessings be upon him) said: "This is a vein; it is not menstruation. When your menstruation comes, leave the prayer, and when the menstruation ends, wash the blood off yourself and pray."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4084