Background: Ductoscopy is a minimally invasive procedure, using a sub millimeter fiber optical camera, to explore the mammary ductal epithelium for Pathological Nipple Discharge (serous fluid discharged from the milk duct) and breast cancer, detecting lesions up to eight years before other modalities. Although ductoscopy can revolutionize breast disease screening, an improved method to take a biopsy during the procedure is needed. The goal of this study was, therefore, to develop a new biopsy method for the removal of a small tissue sample during ductoscopy for the pathological examination and a definite diagnosis. Method: In order to develop the novel biopsy instrument the clinical situation and cutting forces were analyzed. The novel biopsy instrument, contains ∅1:0x0:1 mm and ∅1:2x0:1 mm needles including a knife design at the tip. The needles are actuated by the handle design, able to create a single- and a counter rotating motion. Subsequently the fully functioning prototype has been evaluated on its mechanical functionality and biopsy capabilities. In these experiments three different tip geometries: The Straight-, Beveled- and Reverse beveled-knife, were evaluated based on the resection time, displacement, operation force Biopsy points and sample volume. To mimic the ductal wall and tumorous tissue, gelatin with a Young’s modulus of 150 kPa was used. Results: Comparison of the two rotational configurations demonstrated a decrease in all tested variables (resection time, displacement and tissue cut angle), using the counter rotation configurations. The Beveled tip designs showed an inability to debulk the lesion, however the other two geometries, the Straight and Reversed beveled tip proved to be able to debulk the breast mimicking phantom. The resected volume was 1:0 mm3 sufficient for future pathological examination. Conclusion: The experiment has revealed the potential clinical application of the instrument to debulk lesions found in the mammary ductal epithelium. Even so, more knowledge on the biomechanical properties of the lesions and an in-vivo experiment is needed, to find an optimal knife design for the different clinical situations. In future the novel instrument could be combined with a ductoscope, improving the diagnosis of breast cancer patients in an early stage of the disease.