Lavayana 29 year old woman presents with a single 2 cm by 2 cm lump in the breast. The lump is mobile and hard in consistency. On examination, the mass is painless and there is also palpable lymph node in the axilla. An ultrasound was performed which shows a mass with hypoechoic, ill-defined, spiculated and microlobulated margins. A mammogram shows ill-defined, spiculate borders. A fine needle aspiration cytology was performed which results came back as normal. What is the SINGLE most appropriate investigations to confirm the diagnosis?