Needle biopsy is a simple, reliable, inexpensive, well tolerated, and minimally invasive procedure for the diagnosis of tumors both in superficial and deep sites. In the new scenario determined by a more conservative approach to tumor treatment, and in the era of 'tailored' or 'targeted' oncological therapies the use of this technique is expected to increase dramatically for the diagnosis of neoplasia in all different phases of the disease. The efficacy of needle biopsy is, however, strongly influenced by the experience of the physician performing the technique and by the pathologist's attitude towards the interpretation of such minimal cellular harvest. Aim of this volume is to provide all possible clues for the optimization of the needle biopsy diagnosis. By using a problem-oriented approach, the best interventional maneuver and sample triage will be described for all types of lesions, and the interpretation of all possible cytological findings will be supported by the pattern analysis methodology. The reader will be guided to pattern recognition in the cellular sample and to provide the most correct interpretation, based on the integration with clinical and preanalytical data.