Could you tell me what are chances of suspicious lump in mammogram being cancer?

Ultrasound: The details are a bit too broad to give you a good answer. Often an ultrasound is done for a suspicious lump to further characterize the lump as solid or filled with fluid (cyst). If the lump has very irregular edges and/or associated suspicious calcifications a biopsy may be advised without an ultrasound. This may give you some help in talking about your findings with your doctor.

Much depends: on the specific mammographic characteristics of the mass with respect to the probability of cancer, but in general a BIRADS category 4 (suspicious) lesion has about a 30% positive predictive value for malignancy. This means 70% of the time it is benign. A category 5(highly suspicious) lesion has a 95% positive predictive value for cancer.