BIRADS IV suggesrs there is suspicion of malignancy. Patient should undergo a biopsy or fnac  for confirmation

I would definitely recommend a trucut biopsy. In case lump is small than USG guided otherwise if it easily palpable can be done without USG as an OPD procedure . There is a significant probability of it being malignant in case biopsy is inconclusive would mandate an excision biopsy as next step.biopsy should be preferred over fnac.