Grey zone lesions of breast: Potential areas of error in cytology.

Fine-needle aspiration cytology (FNAC) of the breast is a rapid, cost-effective, and sensitive procedure to diagnose breast lesions, and was widely employed to diagnose breast lesions in the past. However, in recent times, core needle biopsy of the breast is gaining popularity and acceptability, although FNAC still looms large. There are some intrinsic disadvantages to FNAC, of which the most important is probably difficulty in classification of a significant percentage of breast lesions. Such lesions are usually denoted by the rubric "grey zone lesions of the breast." This article attempts to review these grey zone lesions and highlight the difficulties in diagnosing them.