Recent trends in the management of early breast cancer have moved toward breast conservation, without a loss in disease-free intervals or overall survival. The in situ ablation of breast tumors without the need for lumpectomy is the next logical extension of this trend. Advances in stereotactic guided localization, ultrasound and magnetic resonance imaging (MRI) technology has markedly improved our ability to visualize, biopsy and possibly treat breast tumors. With these technologies, probes for delivery of energy for ablating tumors and for monitoring the effect can be placed precisely within breast tumors. Several methods are available to destroy tumors in situ, based on thermal destruction of tumor with either heat or cold. Cryoablation is performed using a liquid-nitrogen cooled needle. Heating techniques include delivery of the heat through probes placed in the lesion to conduct radiofrequency irradiation or laser light energy. Two techniques, focused ultrasound and focused microwave thermotherapy, are truly non-invasive in that they do not involve any skin puncture. In addition to the incentive of eliminating lumpectomy from the treatment paradigm for early stage breast cancer, and the potential cosmetic advantages, in situ ablation may also provide an immunological benefit by providing a source of antigens for the development of a systemic anti-tumor immune response. The augmentation of this response may provide an advantage to in situ ablation in terms of recurrence and survival rates.